BULLETIN OF THE FLORIDA STATE MUSEUM BIOLOGICAL SCIENCES Volume 6 Number I POSTCRANIAL OSTEOLOGY OF THE WATERFOWL Glen E. Woolfenden 6<0~1-i--..4,Juu -I = F » UNIVERSITY OF FLORIDA Gainesville I96I Numbers of the BULLETIN OF THE FLORIDA STATE MUSEUM are pub- lished at irregular intervals. Volumes contain about 800 pages and are not necessarily completed in any one calendar year. WILLIAM J. RIEMER, Managing Editor OLIVER L . AUSTIN, JR., Editor Consultants for this isaue: Hildegarde Howard Jean Delacour Communications concerning purchase or exchange of the publication and all nianuscripts should be addressed to the Managing Editor of the Bulletin, Florida State Museum, Seagle Building, Gainesville, Florida. Published 28 June 1961 Price for this issue $1.60 POSTCRANIAL OSTEOLOGY OF THE WATERFOWL GLEN E. WOOLFENDEN2 SYNOPSIS: Postcranial osteology of nearly all the genera of waterfowl of the worId is described. On. the basis of this study certain changes in the classifica- tion within the order are proposed. In comparison. with the most recent classifi- cation of the waterfowL that of Delacour, the. following changes are proposed: Anseranas is placed in a monotypic family; Stictonetta is removed from the Anatini and placed tentatively in the Dendrocygnini of the Anserina6; Cereopsis is moved from the Tadornini to a monotypic tribe of the Anserinae; Plectropterus is moved from the Cairinini to the Tadornini; Tachyeres is moved from the Tadornini to the Anatini; the tribe Cairinini i5 merged with the Anatini; Mer- ganetta is moved from the Anatini to a monotypic tribe; Rhodonessa is moved from the Anatini to the Aythyini; the tribe Somateriini is merged with the Mergini. The following genera are rdurrected: Olor, Nesochen, Cattonetta, Pteronetta, Metopiana, Mergellus, Lophodytes, and Nomonux, and, tentatively, Asafcornis and Satua,lorina. TABLE OF CONTENTS Page Introduction - 2 Acknowledgments Materials and methods 8 Descriptive osteology 5 Humerus 6 Carpometacarpus 21 Sternum 84 Coracoid 46 Scapula 59 Furculum 64 Femur - 66 Tibiotarsus ~- 73 Tarsometatarsus 79 Pelvis 86 Vertebral column 89 Discussion and conclusions 95 Appeadix: Ligaments of the pectoral girdle 124 Literature cited 126 i The author, Instructor in Biological Sciences at the University of South Florida, Tampa, completed this work while a graduate student and an instructor at the University of Florida, Gainesville, An earlier version formed his doctoral disserta. tion and was accepted by the Graduate School in August 1960. Manuscript sub- mitted 19 December 1960.-ED. 2 BULLETIN FLORIDA STATE MUSEUM Vol. 6 INTRODUCTION It seems logical that the waterfowl, as the Anatidae are commonly known, should be a well-studied group. They have great economic and recreational value, and many species are easily reared in captivity. No living species completely new to science has been discovered since 1894. But, as Delacour and Mayr (1945) point out, their internal anat- omy is a completely neglected field. Until Verheyen's osteological work (1955), no modern comparative anatomical study of all the taxa within the family was ever undertaken. Verheyen bases his classification almost entirely on the number of vertebrae in the different regions of the column and On relative lengths of various limb elements.' He admits that structural details of the in- aividual bones are of great importance to pa[leontoldgists, but further states, somewhat antithetically, that such features rarely serve to dis- tinguish one waterfowl from another. Previous work with anatid fos- sil material convinced me that a detailed analysis of the structure of their bones might contribute .signifcantly to better understanding of waterfowl phylogeny. Many osteological studies emphasize the relative lengths of limb bones. This characteristic may be of significanee between closely re- lated species, but in such ancient and diverse groups as the waterfowl, it seems likely that relatively similar proportions could have arisen in- dependently several times. The concept that structural features of the different elements may be more significant than relative sizes underlies this study. As the skull is treated by other investigators (Verheyen, 1955; Good- man and Fisher, MS), the present study is based primarily on quali- tative structural differences in 10 postcranial elements. The relative taxonomic usefulness of these elements is respectively: humerus, car- pometacarpus, coracoid, sternum, tarsometatarsus, femur, tibiotarsus, scapula, pelvis, and furculum. Size and Other characters of a specific nature variable within the genus are disregarded. The ulna, radius, and fibula are generally considered of lesser taxonomic value and were not studied. Anatomical nomenclature follows Howard (1929). In a few in- stances it has been necessary to name other features. When an addi- tional term is first used, it is defined or a reference is cited. ACKNOWLEDGMENTS I extend my deep appreciation to Professor Pierce Brodkorb for his valuable and untiring supervision throughout the course of the problem. 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 8 Sincere thanks are also due to the 6ther biologists who critically read the manuscript, Oliver L. Austin, Jr., Jean Delacour, J. C. Dickinson, Jr., Hildegarde Howard, Roland F. Hussey, and James N. Layne. To Ted T. Allen, who made the drawings, and Robert W. MeFarlane and J. Hill Hamon, wbo did the photographic work, I am also grateful. Finally, I wish to acknowledge financial aid frem a grant from the Sig- ma Xi-RESA Research Fund and also from Lester B. Woolfenden and Gwen S. Woolfenden. MATERIALS AND METHODS The skeletal collection of Pierce Brodkorb was supplemented by ma- terial borrowed from the American Museum of Natural History, United States National Museum, National Museum of Victoria, Australia, and Peabody Museum of Natural History; these specimens were Obtained through the kindness of Dean Amadon, Herbert Friedmann, A. R. MeEvey, and Philip S. Humphrey, respeetively. Additional material was donated by Richard G. Naegeli, Director Of Busch Gardens, Ethel L. Woolfenden, Joseph R. Jehl, Jr., Charles T. Collins, William O. Wirtz II, and Henry M. Stevenson, Jr. Norman L. Ford sent data from specimens in the University of Michigan Museum of Zoology. Over 85 percent of the currently recognized genera were studied. Only 8 of the 62 genera recognized by Peters (1931) were unavailable, namely Cyahochen, Asarcornis, Stictonetta, Pseudotadorna, Nesonetta, Saluadorina, Camptorhynchus, and Thalassornis. By Delacour's classi- fication (1954, 1956, 1959) only 5 of his 41 genera were lacking, namely: Cyanochen, Stictonetta, Lophonetta, Camptorhynchus, and Thalas- sornis. The assembled collection of 432 specimens represents 105 of the 167 species of waterfowl recognized, by Peters. Those species and sub- species examined and the number of specimens involved are: Cygnus cygnus 2 Anser anser 1 C. colunibianus 24 A. albifrons albifrons 1 C. buccinator 1 A. fabilis. 1 C. olor 2 Eulabeia indica 1 C. melancoriphus 8 Cugnopsis Cugnoid 2 Chenopis atrata 4 Philacte canagica 1 Anseranas semipal;nata 1 complete + Branta bernicla hrota 6 1 body skeleton B. b. nigricans 1 Plectropterus gambensis 2 B. canadensts canadensis 8 Cereopsis n.hollandiae 2 B. c. hutchinsii 2 Chen caerulescens i B, rufico?lis 1 C . hyperborea 2 Nesochen sanduicensis 1 C. rossii 9 Chlo6phaga melanoptera 4 4 BULLETIN FLORIDA STATE MUSEUM Vol. 6 C. leucoptera 1 Rhodonessa caruophyllacea 1 body C. diapar 3 skeleton Chenonetta fubata 2 Aix sponsa 16 Dendroc!/gna viduata 1 complete + 1 Dendronessa galeficulata 5 body skeleton Cheniscus coromandelianus Coromandel- 0 0 O P P bicotor bicolor 1 ianus 4 gavanica 2 C. putchellus 1 autumnalia autumnalis 1 Nettapus auritus 1 a. discolor 1 body skeleton Pteronetta hartlaubil 1 arborea 3 Heteronetta atricapilla 1 Alopochen degyptiaca 3 Netta ndina 2 Neochen iubata 1 complete + 1 body Metopiana peposaca 8 skeleton Aytht/a ("Nurocd") calisineria 3 Sarkidiornis melanota 1 A. terina 1 Cairina moschata 4 A. americana 5 Coscoroba coscoroba 1 A, collaris 14 Casarca cana 2 A. fuliguta 6 C. tadornoides 1 A. nvroca 1 C . oariegata 2 A. marila marila 21 Tadorna tadorna 4 A. m. nearctica 6 Anas platgrhynchos platy'hynchos 6 A. a#inis 25 A. poecilorhyncha 1 Tach!/eres brachyptera (i.e., pteneres) 1 A. luzonica· 1 Bucephala dangula clangula 2 A. meNeri 1 B. c. americana 5 A. fulvigula fulvigula 7 B. albeola 7 A f. maculosa 1 Clahgula huemalis 5 A. rubripes 6 Histtionicus histrionicus pacificus 1 A. undulata 1, Somateria mollissima u-nigra 1 A. c!/anoptera cyanoptera 8 S. m. dresseri 7 A. discors 10 S. spectabilis 8 A. querquedula 4 Arctonetta lisheri 1 A. castanea 2 Oidemia nigra nigra 8 A. crecca crecca 1 0. n. americand 1 A. c. carolinensts 10 Melanitta fusca fusca 1 A. formosa 1 M. f. deglandi 5 A. falcata 1 M. perspicillata 1 A. leucophrys 1 Polt/sticta stelleri 1 A. brasiliensis 1 Hymenolaimus malacorhunchos 1 A. acuta tzitzihoa. 5 Nomont/x dominicus 2 A. angustirostris.1 body skeleton Oxyufa jamaicensis iainaicensis 11 A. bahamensis rubirostris 2 0. uittata 1 Mareca penelope 14 Biziura Iobata 1 M. americaha 4 Mergellus albellus 1 M. sibilatrix 1 Lophodytes cuoullatus 7 Chaulelasmus streperus 9 Mergw merganser merganser 2 Spatula 04,peata 5 M. m. americanus 2 S . platalea 1 M. serrator 18 Malacrohynchus membranaceus 1 com- Merganetta armata armata 2 plete + 1 partial skeleton 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 5 , All the ratios presented are intramembral and reflect relative pro- portions within a given element. Obtained by dividing the width or depth of various portions of the element by its length, the ratios are expressed as percent of the length. Linear measurements are taken to the nearest tenth of a millimeter. The methods of taking the measure- ments are explained where first mentioned under each element. DESCRIPIIVE OSTEOLOGY Listed below are the genera of Anatidae according to Peters (1981), ar- ranged in the subfamilies and tribes of Delacour (1954, 1956, 1959). Two generic changes (Authya for Nyroca, cf. American Orinthologists' Union, 1945; Lampronetta for Arctonetta, Of. Parkes, 1955), and two additions (Lophonetta and Amazonetta from Anas, cf. Delaeour and Mayr, 1945) are incorporated. Parentheses enclose the genera not rec- ognized by Delacour, and these follow the genera with which they are synonymized. Asterisks mark tbe generanot available for this study. Where additional genera are mentioned in the text an authority is listed. I have altered slightly the vernacular names of certain of the tribes and the arrangement of the tribes in the subfamily Anatinae. The latter change allows fot clearer presentation of the osteological data which follow this arrangement: Subfamily Anseranatinae (Pied Goose) Anseran-as. Subfamily Anserinae (Whistling Ducks, Swans and Geese). Tribe Dendrocygnini (Whistling Ducks) Dendrocvgna. Tribe Anserini (Swans and Geese) Cdscoroba; Cygnus, (Chenopis); Anser, (Cugnopsis), (Chen), (Philacte), (Eutabeia); Branta, (Nesochen) Subfamily Anatinae (Ducks). Tribe Tadornini (Sheldrakes) Cereopsts; Chloaphaga; Cyanochen®; Neochen; Alopochen, Tadorna, (Cbsarca), (Pseudotadorna)*; Lophonetta®; Tacht/eres. ' Tribe Anatini (Dabbling Ducks) Anas, (Nesonetta); (Chautelasmus), (Mareca), (Spatula), (Satuadorina)'; Rhodonessa. Malacorhvnchus; Hymenolaimus, Mer- ganetta, Stictonetta*. Tribe Cairinini (Perching Ducks) Amazonetta; Chenonetta; Aix, (Dendronessa); Nettapus, (Cheniscus); Sarkidiornis; Cairina, (Asarcornis)6, (Ptetonetta); Plectropterus, Tribe Aythyini (Pochards) Netta, (Metopiana); Authya, Tribe Somateriini (Eiders) Polusticta; Somateria, (Lampronetta). Tribe,Mergini (Sea Ducks) Melanitta, (Oidemia),· Camptothunchus®; Histrionicus; Clangula; Bucephala; Mergus, (Mergellus), (Lophodytes), Tribe, Oxyurini (Stiff-tailed Ducks) Ox!,ura, (No,nonyx), Thalassornis®; Biziura; Heterolietta. t 6 BULLETIN FLORIDA STATE MUSEUM Vol. '6 - Hurnerus Paleontologists and osteologists generally consider the humerus in birds to be extremely useful taxonomically. Of the 10 elements described herein, it shows the greatest number of characters of systematic value. ANSERANATINAE The pied,goose (Anseranas semipalmata) differs from ail other Anatidae by three humeral characteristics: (1) The prominent capital shaft ridge (Ashley, 1941) is situated more medially. Correspondingly, the at- tachment of the external head of the triceps is restricted; it barely ex- tends proximally to the base of the internal tuberosity. In all other waterfowl it extends past the tuberosity toward the head of the hum- erus. (2) The pneumatic fossa is greatly reduced. The fossa does not extend to the humeral head, and the floor is elevated from the bicipital surface. (8) The facet for the anterior articular ligament is less elevat- ed, particularly along the inner margin. Because of its superficial resemblance to Plectropterus, Delacour and Mayr (1945) treated Anseranas as an aberrant member of the perch- ing ducks . Further consideration led Delacour ( 1954) to place Anser- anas in a separate subfamily on anatomical evidence presented by Boetticher (1943), who considers several skeletal features important. The structure of its humerus shows Anseranas to be a primitive anatid, and completely justifies its removal from the Anatinae. ANSERINAE Delacour and Mayr place the whistling ducks and swans and geese in the same subfamily. Similarity in the form of the humeral head in Dendrocygna and certain geese has been noted previously (Wetmore, 1924). The prominent capital shaft ridge directed towards the humeral head, coupled with an area of attachment for the external head of the triceps that extends virtually to the humeral head, characterizes the. subfamily. In the Anserinae and Anseranatinae the area of pectoral at- tachment on the external tuberosity is elevated and somewhat circular; in the Anatinae it iies essentially flush with the proximal portion of the shaft and is elongate. In the Anserinae and the Anseranatinae the cap- ital groove is not extensive, whereas in the Anatinae it extends laterally over the anconal surface and undercuts the head considerably. TRIBE DENDROCYGNINI (WHISTLING DUCKS). The humerus of whistling ducks can be distinguished from those of the swans and geese, and also of Anseranas, by the width of the space between the external condyle and the facet for the anterior articular ligament in relation to the facet's 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 7 -'.- 35*.8 r , j f j 0% ,« I .- \ f 4 7 j/ , 4/1 1 I.- 4.2 ~1 1 , FIGURE 1. Right humerus, anconal view. Top row: Anseranas sen*i/)almata, Dendrocugna autumnalis, Cugnus melancoril)hus, Branta bernicla, Cereopsis n. hollandiae. Bottom row : Chloepliaga melanoptera. Anas platy ,·hunchos, Aterga- netta armata, Auth!/a marila, Clangula hue,nalis, Ox!/um famaicensis. 8 BULLETIN FLORIDA STATE MUSEUM Vol. 6 width. In the whistling ducks the space is narrower than the facet, whereas in the swans and geese the reverse is true . The small size of the humerus and its prominent capital shaft ridge have been considered distinctive of Dendrocygna. These two features alone, however, do not separate the genus from the smaller true geese. TRIBE ANSERINI (SWANS AND GEESE). The prominent capital shaft ridge, the extension of the area of attachment-for the external head of the tri- ceps almost to the humeral head, and narrowness 6f the facet for the attachment of the anterior articular ligament (narrower than the space between the facet and the external cdndyle) define this tribe. Features ofi the humerus indicate the tribe is comprised of two dis- tinct units, one containing the swans and Coscoroba, the other the geese. These two units are distinguishable by the relative width of the distal end, of the humerus. In the swans the relatively narrow distal end constitutes 12.2 to 18.9 percent of the total length, and in Coscoroba 13.9 percent. In geese the range is from 14.1 to 15.6 percent. Further characteristics distinguishing these two groups pertain to the con:figuration ofthe internal tuberosity afid entepicondyle. (1) The entepicondyle is not extended distally as far in swans as in geese. (2) The entepicondylar prominence is more produced laterally in swans, in part the result of the more medially-situated entepicondyle. (8) The internal tuberosity is shorter and more rounded at the tip in swans. In true swans a short, wide furrow leads transversely from near the proximal end, of the capital groove onto the internal tuberosity; this furrow is indistinct in Coscoroba. Neither Peters nor Delacour recognize the genus Olor as 'distinct from Cygnus. Other authorities (Wetmore, 1951) consider the separa- Mon of the swans into two or more genera warranted. Howard (1946) lists sevdral distinguishing features of the humerus. (I) The inter- muscular line on the capital shaft ridge is short, indefinite, and not turn- ed inward below the head in Cygnus. In Olor the line runs along the ridge and turns inward about 34 inch below the head. (2) The area of attachment of the supraspinatus is clear-cut in outline and situated be- low the pneumatic foramen; it is bordered by a raised line continuous with the median crest in Cygnus (poorly marked in C. melancoriphus). In Olor the attachment is less clearly' marked and spreads past the median crest, and it lacks· the raised bordering line at the edge. (8) The ligamental funrow is broad and shallow in Cygnus olor, but not in C. melancoriphus, whereas in Olor it is narrower and deeper. (4) The attachment of the anterior articular ligament is short, broad, and heav- ily bordered on its outer edge next to the attachment of the pronator 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 9 bfevis in Cygnus. In Olor the attachment is long, narrow, and smooth- ly rounded at the edges. (5) The impression of the brachialis anticus in Olor is short, broad (particularly at the proximdexternal edge) clearly outlined, and usually deeply depressed. In Cygnus the irnpression is less clearly Outlined. The series of swans available to me confirm these features, the iast of which proves particularly useful. Chenopis is sim- ilar to Cygnus-in all these featuifes. The hilmeri of the -true geese, Branta, Nesochen, Anser, Cygnopsis, Eulabeia, Philacte, and Chen are very similar. Two specimens of Cyg- nopsis; both aviary birds, are distinguishable from the Other genera throfigh. the larger, more rounded and distally extended pneumatic fossa which excavates more of the shaft and the bone forming the me- dian rim of the fossa. Miller (1987) was unable to distinguish the humeri of Philacte, Anser, and Chen from one an6ther, but f6und the impressiOn of the] external head of the triceps somewhat useful in separating Nesochen and Branta from these three genera. The impression has a. distinct border in Nesochen and Branta, whereas in Philacte, Anser, and_Chen it is most often indistinct. C!/gnopsis and Eulabeia resemble the latter group in this respect. Miller remarks that Branta shows greater curv- ature distally; with my series this feature is not particularly ziseful. Brodkorb (MS) mentions that the deltoid crest ih anconal view shows a distinct bend in the middle in Branta: whereas in Philacte, Anser and Chen it is more rounded. In a now larger'series of geese we find this feature useful in most cases, but flot infallible. Nesochen and Eulabeia resemble' Branta in this character. One. feature. of the humerus, although not infallible, aids in separ- ating Chen from Anser and Philacte. In Chen the humerus, in anconal view, has the head rotated toward the ihteirnal side,. and thus the lip of'bone extending from the head over the capital groove is more prom- inent. As only two specimens of Anser are available it is difficult to assess the value of this character. ANATINAE Duck humeri lack the prominent capital shaft fidge directed toward the head that is typical of the Anserinae (Cereopsis is an excepti6n, see Tadornini, paragraph 7). A few ducks have a humeral ridge directed toward the external tuberosity, but most lack it. In Anatinae the capi- tal groove extends laterally over the anconal surface and deeply under- cuts the head. The differences in size and position of the capital shaft ridge seem to re5ult from a difference in the attachment of the external head of the triceps, which is stronger in the Anatinae. Miller (1987) 10 BULLETIN FLORIDA STATE MUSEUM Vol. 6 postulates that greater strength of the muscle is indicated by the more lateral position of the ridge in Chlo6phaga (here. placed in the Anatinae) as compared with certain true geese. The structure of the humerus of the Anatifiae indicates that the sheldrakes and stiff-tailed ducks are the two most distinct tribes; where- as the dabbling ducks, perching ducks, pochards, eiders, and sea ducks a-te more' closely related to one another. TRIBE'TADORNINI (SHELDRAKES). The sheldrakes have the following humeral characteristics: (1) The capital shaft ridge is fairly prominent as in Anserinae, but is directed towards the external tuberosity. (2) The area of origin of the external head of the triceps is narrower than in other ducks; as a result the area between the attachment of the muscle and the external tuberosity is elevated. (8) The deltoid crest is latger and more flaring than in 6ther ducks. Furthermore, when compared in lateral view, the entire'crest tends to be·more rounded, and when an abrupt bend is present it lies more posteriad.· (4) The deltoid crest extends flirther distally (most evident when the distal borders of deltoid and, bicipital crests are compared). (5) The head is rotated so that the external tuberosity is usually higher or more anconal in rela- tion to the head than in other ducks. This feature is best seen by view- ing the proximal end of the bdde with the palmar surface lying on a horizontal plane. The external tuberosity represents more than 89 percent of the height of the head in the sheldrakes, with Tachyeres and Neochen as exceptions. (The height of the humeral head is the distance between the plane on which the palmar surface lies and a parallel plane touching the anconal surface of the head). In Neochen,the head is rotated as in other members 6f the tribe, but a robust head results in the external tuberesity constituting only 87.2 percent of the head height. Tachyeres measured 86.2 percent and showed no indication of the rotation present in the other genera assigned to this tribe. - Miller (1937) remarks on the striking modification of Chlo6phaga, namely the much broader depression of the triceps, whieh is directly related to the more lateral position of the capital shaft ridge and the external. flaring of the deltoid crest. A feature he does not mention that further distinguishes Chlodphaga from the, true geese and relates it to the other sheldrakes is the greater elevation of the facet for the anterior articular ligament. Miller (1987) felt that Chloaphaga would prtive to be more closely-related to some anserine other than the N6rth American geese. The relationship appears even more distant than he suspected, and more recent monographers place the genus in a sub- family apart from that containing the true geese. 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 11 Based on humeral characteristics, the seven available genera of sheldrakes fall into five distinct drof~ps: Tadorna and Casarca form one, Chlogphaga and.Alopochen another, and Neochen, Cereopsis, and Tachyeres individually the other three. Tadorna and Casarea cannot be separated by features of the hum- erus. Together they differ from Chlodphaga and Alopochen as follows: (1) The external tuberosity is less prominent as a result of its distal portion lyih g almost f[ush witth the shaft. (2) The external head of the triceps is narrower and the capital ahaft ridge curves ill-ward toward its external edge. In Alopochen and Chlotphaga, where the-external head of the triceps is wider, the capital 5haft ridge is straight and diree ted towards the median edge of the external tuberosity. (8) The distal end of the humerus possesses characters that tend to distinguish Ta- dorna and Casarca from Alopochen and Chlodphaga, but none is con- stant. The lack of an anconal protuberance on the entepicondyle is the most reliable of these. Alopochen differs from ChloEphaga as follows: (1) The capital shaft ridge is more prominent in Alopochen; correspondingly the area be- tween the ridge and the pneumatic fossa is a much more steeply in- clined surface in Chlo6phigd. (2) The ihternal tuberosity is less elevat- ed in Aloljochen (best observed by looking along the shaft towards the pneuniatic fossa). (3) The,facet for the anterior articular ligament is a rounded knob in Alopochen; in Chlotphaga the surface is Hat. The humerus of Neochen is quite different from those· of other shel- drakes, and certain features indicate. a relationship to the dabbling ducks. (I) The depression for the external head of the triceps extends laterally to the external tuberosity. This is characteristic of ducks other thaii sheldrakes; all available sheldrake speBimens have a space between the area of niusele attachment and the tuberosity. (2) The lip extending from the head over the impression f6rmed by the external head of the triceps is curved. In most dabbling ducks it i5 almost straight and perpendicular to the shaft. Chlogphaga and Alopochen show curvature in this area. (3) The deltoid crest is less Haring and more abruptly bent in the middle as in the dabbling ducks, but· ex- tends farther distally, and this is characteristic only of the sheldrakes. (4) The head is rotated as mentioned previously. This feature isunique to the sheldrakes among the ducks. From the characters of the humer- us the position of Neochen remains uncertain, although its strongest affinities do seem to lie with the sheldrakes. The humerus of Cereopsis is more like that of the swans and geese than any of the sheldrakes. It resembles them in the following ways: (1) The capital shaft ridge is extremely promihent and directed towards 12 BULLETIN FLORIDA STATE MUSEUM VoI. 6 the head. (2) The surface for pectoral attachment on the external tub- erosity is elevated from the shaft and, therefore, less elongated than in sheldrakes. (8) The facet for the anterior articular ligament is fess elevated than in sheldrakes. (4) The entepicondylar pr6minenee is laterally produced as in swans. Cereopsis differs from the swans ahd geese as £ollows: (1) The deltoid crest is more evenly curved through- out its length. (2) The head blends in with the shaft instead of being delimited by a depression on the anconal surface. Thus the features of the humerus of ereopsis pdint toward a strong affinity with the swans and geese. The humeral feature that best distinguishes the sheldrakes from the other ducks, the rotation. Of the head, is lacking in the aberrant Tachyeres. In sheldrakes the external tuberosity comprises more than 89 percent of the height of the head. In Tachyeres the external tuberos- ity constitutes only 86.2 percent. Tachyeres has the following addi- tional characteristics: (1) The exeavation for the external head of the triceps is very deep. The depth results in a prominent capital shaft ridge directed towards the external tuberosity. The surface mediad to the ridge upon whith the muscle attaches is steeply inclined, and the proximal extent of the muscle forms ·a deep cavity beneath the hdad. (2) The ikiternal tuberosity is bent distad so that it toilsiderably over- hangs the pneumatic fossa. This striking feature is most evident when the bone is viewed from the internal side, (8) The deltoid crest has the proximal portion condave in anconal view; the distal portion flares wide- ly, and meets the shaft,at an abrupt angle. (4) The brachial depression is indistinct, but covers a wide area. (5) The facet for the attachment of the extensor metacarpi radialis (a depression on the external sid© of the distal end of the humerus immediately proximal to the ectepicondy- lar prominence) is more mediad than in other ducks. TRIBE ANATINI (DABBLING Ducks). The humerus of the dabbling ducks can be, described as follows: (1) The capital shaft ridge is obsolete, in contrast with the sheldrakes. (2) The pneumatic fossa is oyaloid and unrimmed with heavy bone, in coutrast with the perchers (see perching ducks for additional details). (8) The pneumatic fossa is open and contains bony struts (Woolfenden, 1959) instead of being closed as in the pochards (except Netta and usually Metopiana), eiders, sea ducks (except Mergus and Lophodytes),and stiff-tailed ducks. In dabblers the ectepicondyle is equal or subequal in- anconal height to the entepicondyle when. the humerus is placed ona horizontal flat surfaces palmar side down: In the pochards, including Metopiana and Netta, the entepicondyle is distinctly higher. 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 18 Dabblers differ from mefgansers in the form of the internal tuber- osity. In the mergansers, and this is essentially true of all sea ducks, it is shorter and the length (measured perpendicular to the shaft from the ligamental furrow to the tip) is less than the width (measured from the capital groove to the area of attachment of the infraspinatus). No humerAl features have been found that enable the separation of Chaulelasmus, Mareca, and Spatula from the genus Anas. Specimens of Mareca frequently display a robust shaft and a compressed distal condylar area, but these features do not seem consistent enough in large series to merit generic distinction. On the basis of the humerus alone the species Anas leucophrys de- serves segregati6n in a separate genus. The distal condylar area is grossly different from that of the 22 available species of typical dabbiers (Anas, Chaulelasmus, Mareca, Spatula). The name Callonetta, pro- posed as a subgenus by Delacour (1936) for this little-known species can be used (Delacour spells it Calonetta in later publieations [1945, 1956]). Its humerus differs from those found in the aforementioned genera as follows: (1) The shaft is more signioid than in Anas. (2) The distal end is rotated so that, the ectdpicondyle is much more elevated than the entepicondyle. (S) In anconal view the entepicondyle appears distally elongated. In typical dabblers the entepicondyle is generally as high as the eatepicondyle. and is never distally elongated. (4) The deltoid crest is more rounded distally from the bend, instead of being angular as in typical dabblers. Features 1, 2, and 3, and also a robust shaft (8.0 percent of total length) strongly oppose Delacour's suggestion (1956) of the possible afRnities Of Callohetta to the pochards (wherein the shaft varies from 6.0 to 7.0 percent). In certain perching ducks (Nettapus, Cheniscus, and Amazonetta), and sea ducks (Histrionicus and Clangula), however, the rutation of the condyles and thickness of the shaft resemble that of Callonetta. Of these two tribes only the perching ducks have· the open fossa found in Callonetta. The affinities of Malacorhynchus are inconcluSive from its humeral characteristics, which are: (1) The pneumatic fossa is closed as in the diving tribes. (2) The rim of the pneumatic fossa is ovaloid and lacks heavy bone, thus contrasting with typical perching ducks. (3) The facet for the anterior articular ligament is elevated as in dabbling and perching ducks. (4) The rotation of the condyles, which results in the ectepicondyle being slightly higher than the entepicondyle, contrasts with the pochards. (5) The position of the pits for the muscles that attach to the internal' surface of the entepieondyle resembles that found Only in dabbling and perching ducks. 14 BULLETIN FLORIDA STATE MUSEUM Vol. 6 Humenolaimus · and Merganetta have several features in common that distinguish them from all other dabbling ducks. The fact that both genera habitually dive may account for their similarities: (1) The entepicondyle is less flaring and less extended distally. (2) The area for the attachment of the external head of the triceps is more deeply and broadly excavated. (8) The deltoid crest is reduced and more rounded and thus less angular at the bend. (4) The bi'cipital crest joins the shaft at a much wider angle than in other dabblers, particularly in Merganetta. (5) The internal tuberosity is less produced anconally, and possesses a distally directed Rexure. These two genera are best distinguished from each other by com- paring the depth of the ligamental furrow. In Merganetta this is ex- tremely shallow, more so·than in any other anatid, whereas in Hymeno- laimus it appears to be of normal depth. The brachial depression, al- though not deep in Merganetta, covers a larger area than is character- istic of the tribe. Lastly, Merganetta has the facet for the anterior articular ligament less elevated than Hymenolaimus. Rhodonessa has humeral characteristics intermediate between those of the dabljling ducks and the closely related pochards. The following features are worth noting: (1) The shaft is intermediate in width (7.0 percent of total length) between dabbling ducks (average 7.44 per- cent) and pochards (average 6.88 percent). (2) The facet for the anter- ior articular ligament is less elevated than in dabblers, but more eleva- ted than in pochards. (8) The entepicondyle has a more prominent pro- cess on the anc6nal surface than in any other dabbling duck. In this respect Rhodonessa resembles the pochards, for When the humerus is viewed from this distal end with the palmar surface lying flat, the en- tepicondyle is more elevated than the ectepicondyle. The reverse is true of the dabbling duck. TRIBE CA[RININI (PERCHING DUCKS). The most trenchant feature of perching duck humeri is the rim of the open pneumatic fossa. This tribe shows a definite trend toward a reduction of the fossa to a re- stricted, circular opening rimmed with heavy bone. In the extremely similar humeri of dabbling ducks the fossa becomes ovaloid by an up- ward extension into the internal tuberosity. The shaft of the humerus in many perching ducks tends to be more robust so that the range for the available genera (all but Asarcornis) is from 6.7 to 8.7 percent of the total length, with an average of 7.81. The ratio in the aberrant Plec- trot*erus is 5.7 and 6.8 percent. Chenonetta, Nettapus, and Cheniscus are similar and can be dis- tinguished from other perching ducks in several ways: (1) The proxi- 1961 WOOLFENDEN: OSTEOLOGY OF WATERF6WL 15 mal end of the humerus is inflected to give, a more sigmoid appearance of the shaft. (2) The prominent deltoid crest is more Haring and the head is seemingly less prominent. (8) The pneumatic fossa is more re- stricted. When the humerus is viewed from the internal side down a line perpendicillar to the. shaft and passing through the internal tuber- osity, the fossa can scarcely be seen. In other perching ducks one can normally see into the fossa when the humerus is so orientated. (4) The , distal c6ndyles are rotated so that in distal view the ectepicondyle is elevated above the entepicondyle. Sarkidiornis and Amazonetta also have this feature. Nettapus and Cheniscus, whose humeri are indistinguishable on qualitative features, have the entepicondylar prominence distally pro- duced and the facet for the anterier arficular ligament more flush with the shaft' than does Chenonetta. Otherwise the sinfilarity between these three genera is striking. Chenonetta, Nettapus and Cheniscus share with Aix, Dendronessa, Cairina, and Pteronetta a differeace in the form of the head as com- pared with other perchers. In these genera the depression formed by the external head of the triceps is indistinet along fhe internal edge of the external tuberosity, and blends with the external portion of the head. In Amazonetta and Sarkidiornis the depression is distinct and extends to the external tuberosity, as in the dabbling ducks. Aix. Dendronessa, Cairina, and Pteronetta have additional similar- ities in the form of the humerus. The shaft is curved in these genera in.contrast to Sarkidiornis, but the head is not inflected, in opposition to Chenonetta, Nettapus, Cheniscus, and Amazonetta. Cairina and Pteronetta differ from Aix and Dendronessa through greater overhang of the lip over the eapital groove. Otherwise the humeri of these four genera are qualitatively extremely similar. Fur- thermore, all would be difficult. to separate from the typical dabblers if it were not for differences of the f6ssa and the area of attachment of the external head of the triceps. The humeri of Aix and Dendronessa are indistinguishable. A few minor differences in the prdximal end exist between Ptero- netta and Cairina. (1) In~ Pteronetta the depression for the external head of the triceps extends farther laterally, whereas Cairina shows an elevated area immediately medial to the external tuberosity. (2) In Pteronetta the deltoid crest extends farther out the shaft than in Cairina. This is best seen by comparing its distal extent with that of the bicipital crest. The humerus of Amazonetta can be distinguished from those of typical dabblers quite easily. Amazonetta has the same pronounced 16 BULLETIN FLORIDA STATE MUSEUM Vol. 6 sigmoid curvature of the shaft, with the flaring deltoid crest and in- Hected head as do Chenonetta and Nettapus. In Atizazonetta the dis- tal 06ndyles tend to be rotated so that in distal view the ectepicondyle 0 elevated above the entepicondyle, as in Callonetta. Certain features of the humerus of Amazonetta show greater re- semblance to the dabbling ducks than to the perching ducks. (1) The pneumatic fossa is ovaloid. (2) The depression for the external head of the triceps is excavated to the external tuberosity instead of blending with the head laterally. 'The humeral characteristics of Amazonetta. leave its position in the Anatinae somewhat in doubt; but certainly it is generally distinct from Anas. Sarkidiornis has the constricted, round pneumatic fossa that char- acterizes the tribe, but differs from typical perching ducks in havitig the depression for the external head of the triceps distinct and extend- ing to the external tuberosity as in the dabbling ducks. Sarkidiornis differs from all other perching ducks in that the shaft 66 the humerus is very straight. . The species also has the distal portion of the external tuberosity elevated so that the plane which passes through the area of pettoral attachment almost parallels the plane of the shaft. Further- more, the bicipital. crest is more rounded and meets the shaft at almost a right angle. Several humeral features of Plectropterus suggest its closer afanity to: the sheldrakes than the perching 'ducks. The head. is rotated as in the sheldrakes, although the external tuberosity measures less than 89 percent of the total height of the head in the two specimens available. Another sheldrake, feature is the rather prominent capital shaft ridge directed towards the external tuberosity. The shaft of the humerus, thick in the perching ducks, is thin in Plectropterus (5.7 to 6.8, percent of the total length), not only thinner than in the perchers, but even thinner than in. the sheldrakes. TRIBE AYTHYINI (PO€HARDS). The iinportant differences between the pochards and the closely similar eiders and sea ducks are associated with the distal end of the element. The pochards have the following characteristics: (1) The impression for the brachialik anticus is usually a well-formed depression with the distal medial rim sharply defined. Stettenheim (1958) uses this feature to distinguish.Aythya from similar- sized Clanguld and Lophodytes. (2) The distal condyles are ratated so - thatthe entepicondyle is higherthan the ectepicondyle when the palmar surface is lying fat. As a result the palmar f[oor of the olecranal fossa lies alntost parallel to the flat surface in the pochards, whereas in the eiders and sea ducks a considerable angle is formed. The angle ih 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 17 eiders and sea ducks results from pronounced rotation of the coadyles in the opposite direction from that in pochards. (8) .In pochards the intercondylar furrow B essentially confluent with the olecranal fossa without the transverse ridge that separates them in the eiders and sea ducks. With the exception of the closed pneumatic fossa, the humerus of Af/thi/a is similar to dabbling duck humeri. However two additional features seem useful: (1) The shaft is relatively thinner (6.0 to 6.9 per- cent 6f total length, average 6.33) than in typical dabblers (6.7 to 8.4 percent, average 7.44). (2) The facet for the anterior articular ligament is less elevated. Humeri of species in the genus Ayth!/a are extremely similar, vary- ing significantly only in total length. The width of the shaft and the width through the distal end, given as percentages of the total length, range:from 6.0 to 6.9 and from 18,9 to 15.8 respectively for 27 speci- mens of Aythya marila. The ranges for 45 specimens of seven other species of Aythya fall within those obtained fer the one species. Metopiana and Netta, which possess open fossae, show their affili- ations to the genus Aythya in the shape and elevation of the anconal portion of the entepicondyle. As previously mentioned, in distal view the entepicondyle is higher than the ectepicondyle. In Metopiana (6.8 t66.9) and Netta (6.7 to 7.0), the shaft is intermediate in width between Agthya (6.88 average) and the typical dabblers (7.44 average). Ele- vation of the facet f6r the anterior articular ligament is also inter- mediate between the low one found in Aythya, and the bigh one of typical dabblers. The differences between the humeri of AYetopiana and Netta are of generic magnitude. In Metopiana the bicipital crest arises more abruptly from the shaft, and the head is more robust than in Netta. In Metopiana the head comprises from 7.6 to 7.8 percent of the total length, whereas both specimens of Netta have a percentage of 6.6. TRIBE' SOMATERIINI (EIDERS). Delacour and Mayr (1945) placed the eiders and sea ducks in one tribe. In his later work Delacour (1956) states that the affinities of the eiders lie more with the dabblihg ducks and places them in a separate tribe near this group. Humphrey , (1958a) published evidence in support of the change. Structurally the humeri of eiders and sea ducks are Very similar. They differ from those of the dabbling ducks in a number of significant characters. (1) The pneumatic fossa is closed in the eiders, and with two exceptions, in the sea ducks. (2) The internal tuberosity is short and deep. (8) The facet for the anterior articular ligament is lower. 18 , BULLETIN FLORIDA STATE MUSEUM Vdl. 23 1 (4) The pit for the origin of the pronator longus (the distal pit nearest the anterior articular ligament) extends farther proximally. (5) The pit for the origin of the pronator brevis (the most proximal of the three pits situated on the internal side of the entepicondyle, also see Howard [1929, fig. 21]) is situated farther distally. The last three features reduce the area occupied by the entepicondylar prominence, a trait characteristic of sea ducks. Delacour and Mayr (1945) place the four eider species in one genus, Somateria: Humphrey (1958a) agrees that Lampronetta should be synonymized, but maintains that Polysticta is generically distinct, a judgment followed by Delacour ( 1959). The fbrm of the humerus sup- ports this conclusion. No features of the humerus Were found to sep- arate Lampronetta from Somateria, but in Polysticta the distal end is much more str6ngly,rotated. As a result the anconal portion of the ex- ternal condyle is elevated above the entepicondyle. The only other ducks with a similar degree of rotation of the distal end are Clang-ula and Histrionicus of the sea ducks. Thus the distinctness of Polusticta brought forth by Humphrey also points to a close relationship of the genus to certain sea ducks. Becatise eiders and sea ducks are simjlar in the form of the humerus, the eiders are included in the discussion of the sea ducks which follows. TRIBE MERGINI In Oidemia this measurement varies from 13.9 to 14.4 percent of the total length, in Melanitta the range is· 14.5 to :15.8 percent. In mergansers the deltoid crest is large and sharply angular. Typ- ically, when the humerus of a mei*nser· is·placed palmar surfacd down on a Rat surface, Only the angle in the middle of the crest touches the surface. This contrasts sharply with the humerus of the closely related Bucephala, in which the deltoid crest is small and roundedat the bend. Mergellus is the most distinct of the merganser genera in qualita- tive features of the humerus. The deltoid crest, although angular, is not as large as in Mergus and Lophodytes. The pneumatic f6ssa is clesed, whereas it is always open (Merglis), or almost always open (Lophodytes) in the others. Mergellus differs from the similarly-sized Lophodytes in still other ways. The relative width of the shaft is 6.4 percent of the total length in Mergellus, from 7.1 to 7.7 percent in Lo- phodytes. The relative width of the distal condyles in Mergellus is 14.4 percent of the total length, in Lophodytes 15.6 to 17.8 percent. Other than size the most obvious feature separating Lophodutes and Mergus is the shape of the humeral shaft. In Lophodytes the shaft is distinctly more sigmoid in anconal view thah.in Mergus, in which it is straighter than in most other ducks. The humeri of the two species of Mergus examined are separable by the width of the shaft relative to its total length (Wetmore, 1948). Four specimens of M. merganser range from 7.0 to 7.3 percent. In'17 specimens of M. serrator the range i5 5.6 to 6.9 percent. Bucep/mla differs from Somateria and Lampronetta in having great- er curvature of the shaft, and a more restricted, e16sed pneumatic fossa. In Somateria, although the fossa is closed, it is rather deep. TRIBE OXYURINI (STIFF-TAILED D~CKS). The humerus of the stiff-tailed ducks shows the tribe to be very distinct among the Anatinae. Howard (1946) commented on the ease with which Oxyura jamaicensis can be distinguished from all other (i.e. North American) ducks, and this spe- cies has many features in common with the, other genera assigned to the tribe. The tribe is' unique in the following ways: (1) The pneumatic fossa is shallow, barely reaching the head, and has numerous fora- 20 BULLETIN FLORIDA STATE MUSEUM Vol. 6 mina piercing the walls. In other ducks the fossa may be closed or open, but if closed it is not. as shallow, nor is it pierced by an abun- dance of foramina. (2) The scar for the latissimus dorsi posterioris lies essentially in line with the outer edge of the pectoral attachment. In all other Anatidae the Bear lies far mediad to the outer edge of the pec- toral attachment. (3) The entepicondyle is reduced, as is the pit for the flexor carpi ulnaris (the distal pit farthest from the anterior articular ligament). Oxgura possesses the following identifying features: (1) The surface for the external head of the triceps is deep, and broadly excavated. (2) The distal portion of the external tuberosity is elevated so that the surface for pectoral attachment lies in a plane that almost parallels the plane of the shaft. (8) The shaft is thin (5.2 to 6.0 percent of the total length). (4) The facet for.the anterior articular'ligament is only slight- ly elevated from the shaft, and is distinctly turned towards the internal edge of the element. (5) The external condyle has a ridge extending toward the brachial depression. Nomonyx appears less Specialized than Oxyura. It may be distin- guished from Oxyura as follows: (1) The internal tuberosity is elongate instead of very short. (2) The facet for the anterior articular ligament is more elevated and faces palmad instead of internally. (8) The de- pression for the external head of the triceps is less excavated. (4) The distal portion of the external tuberosity is less elevated and therefore 1 less distinct from the shaft. The one available complete humerus has the shaft thin (6.Opercent of total length), but thicker than in most of the 13 specimens of Oxyura. The humerus of Biziura shows it to be definitely a stiff-tailed duck: (1) The pneumatic fossa is shallow and perforated. (2) The distal por- tion of the external tuberosity is elevated from the plane of the shaft. (3) The shaft is thin (5.5 percent of the total length). (4) The facet for the anterior articular ligament is turned towards the internal edge of the element. Many features of generic magnitude occur on the humerus of Biziura: (1) The depression for the external head of the triceps is re- stricted to an area well below the head and mediad to the capital shaft ridge. Thus the head blends in with the shaft instead of being delimit- ed by a distinct lip as in Oxyura. (2) The external tuberosity has the distal portion even more elevated than in Ort/ura, and as a result the area of pectoral attachment is more rounded and less elongate than in other genera. The external tuberosity is further accentuated because the proximal portion of the deltoid crest ben'ds inward under the tuber- osity. (3) The scar for the latissimus dorsi posterioris lies largely distal 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 21 to the bicipital crest. (4) The ectepicondyle is greatly reduced, without the groove between it and the external condyle present in all other duck5. (5) The entepicondyle is very small, and on the internal edge only one large pit is evident. (6) The brachial depression is broad and rounded distally. In other stiff-tails the distal end of the depression is usually pointed. (7) The ridge extending from the palmar tip of the external condyle, described above for Oxyt#a, is indistinct. Strong evidence supports placing the genus Heteronetta with Oxy- ura, Nomonux, and Biziura. The humerus has the trenchant character- istics of the tribe, namely the shallow, abundantly perf6rated pneumat- ic fossa and the laterally situated scar for the latissimus dorsi posteri- oris . The degree of development of certain features of Heteronetta suggest it to be the least specialized member of the tribe: (1) The entepicondyle is reduced, but not to the extreme exhibited by Oxyura and Biziura. (2) The shaft is thin (6.8 percent of total length), but thicker than in any other stiff-tail. (8) The facet for the anteri6r articu- lar ligament is low, but not as low as in other stiff-tailed ducks. (4) The plane of the surface for the pectoral attachment is inclined to the plane of the shaft, more as in Anatinae other than the stiff-tailed ducks. (5) The area of attachment of the external head of the triceps is reduced and blends in with the head, and it lacks the depression and Over- hanging.lip of the other stiff-tails. (6) The scar for the latissimus dofsi posterioris is situated laterad, but not as far as in other stiff-tails. The humerus of Heteronetta indicates this genus to be a link between the quite distinct stiff-tails and some other tribe, possibly the dabbling ducks. Carpometacarpus The carpometacarpus is very useful taxonomically because of its many articulating surfaces and muscular attachments. ANSERANATINAE The carpometacarpus of Anseranas has several characteristics that distinguish it from those of all other waterfowl: (1) The carpal trochlea has the lower portion of the external rim unnotched. In all other anatids the outer rim is distinctly notched below. (2) A large pneu- matic foramen is present in the internal ligamental fossa. A similarly situated foramen is present in other waterfowl, but none has it as large. (S) The process of metaearpal I is small. (4) Metacarpal H curves upward distally more than in other waterfowl. (5) The facet for digit II is wider and has a more extended lower, lateral process in cor- respondence with feature 4. (6) Metacarpal III is more curved 1 54 ·· s V 3- 9~Z 1 4. * A I #*-. 1 *Ge , I. ./ FIGURE 2. Left carpometacarpus. Row 1: external view Anseranas semipalmata and Cairina moschata; dorsal view Dendrocugna atitumnalis, Branta bernicla, and Anas rubrives. R()w 2: external view Cygnus· melancoriphus and Branta canaden- sis; internal view Branta canadensis and Cereopsis n.hollandiae. Row 8: external view Tadorna tadorna and Anas rubripes, internal view Anas crecca and Aferga- netta armata. Row 4: external view Authuci a#inis and Clangula hyemalis; ventral view Bucephala albeola and Oxuitra jamaicensi,s. 1961 W.OOLFENDEN: OSTEOLOGY OF WATERFOWL 28 throughout its length, particularly distally. (7) Metacarpal III is un- grooved on the lower proximal surface. (8) The facet for digit III protudes farther distally. In most other anatids this facet does not extend beyond that for digit II. ANSERINAE Two traits seem characteristic of the Anserinae: (1) The upper sur- face of metacarpal II, and particularly the distal half, is flat and the angle fofmed with the external surface is correspondingly rather sharp. In the Anatinae the upper surface is rounded, without sharp angles. (2) The extensor attachme'nt is confined to the tip of the short, but high, process of metacarpal I. In the Anatinae the extensor attachment is longer and extends distally onto the distal edge of the process. TRIBE DENDROCYGNINI (WHISTLING DUCKS). The thin, elongdte carpo- metacarpus of,whistling ducks has the following three features to dis- tinguish it from all Other anatids. (1) Metacarpal II in dorsal view is strikingly incurved. (2) The external rim of the carpal trochlea is only slightly notched. In all other waterfowl, except Anseranas, the external rim is notched distinctly. This character may be evidence of the primitive position of .the whistling ducks. (8) A prominent neck is present between the carpal trochlea and metacarpal III. 1 TRIBE ANSERINI (SWANS AND GEE:SE). The. carpometacarpi of swans and geese agree in: (1) Metacarpal III has a distally pro'kressive ro- tation toward the medial side. (2) The pollical facet has a smalllateral articulating surface. Swans may be distinguished from geese by several carponhetacarpal features: (1) In lateral view the external rim of the carpal trochlea slopes sharply downward from the process of metacarpal I. In geese the angle between the posterior edge of the process of metacarpal I and the upper, external rim of the carpal trochlea is smaller. (2) The pit on the internal ·side below and distal to the pisiform process is sep- arated by a raised area from the intermetacarpal space. (8) The pro- cess 6f metacarpal I is lower and has a proximal edge that usually slopes toward the carpal trochlea. In geese the process is higher and the proximal edge is nearly perpendicular to the shaft. (4) Metacarpal II has Only a slight depression on the external surface immediately proximal to the facet for digit II; in geese the depression is deeper. (5) The external rim of the facet for digit II is widely rounded; in geese this edge is almost straight. Coscoroba resembles the true swans in all five of these character- istics. It can be separated from them by differences in the lower, 24 BULLETIN FLORIDA STATE MUSEUM ' VoI. 6 distal portion of the carpal trochlea. (1) The cuneiform fossa (Brod- korb, 1958b), which lies between the rims of the carpal trochlea dis- tally, is delimited proximally by a ridge that extends medially from the external rim of the carpal trochlea. In true swans the ridge is lacking and the fossa extends proximally between the two rims. Howard (1946) lists three criteria for separating the carpometacarpi of Olor and Cygnus; all seem weak in the series of specimens I have studied. Listed in a sequence of decreasing usefulness these are: (1) Cygnus has the external crest of the trochlea short, and the lobe at its distal edge appears aborted in comparison with Olor. (2) Cugnus has the process of metacarpal I straighter and more evenly swollen at the tip, whereas in Olor the process inclines more definitely toward the inner side. (8) Cygnus has the area below the pisifonn process exca- vated into a distinct pitlike depression, the posterior rim of which is prominent. In Olor the area is roughened, sometimes depressed, but it tends to slope away toward the posterior face without an intervening rim. Additional criteria were found more useful in my series: (4) The cuneiform fossa is deeper, and has a distinct proximal and medial rim in Cygnus. In Olor the rim is indistinct, the fossa gradually inelining to the surrounding areas. (5) Metacarpal I has a deeper depression on the external surface immediately proximal to the facet for digit II in Cygnus, and thereby more closely resembles geese. In Olor this area is noticeably shallower. Chenopis is similar to Cygnus in all of the char- acteristics discussed above. No criteria of the carpometacarpus are apparent to enable qualita- tive separation of the several genera of true geese (Anser, Cygnopsis, Chen, Philacte, Eulabeia, Branta, Nesochen). The shorter, broader facet for digit III attributed to Chen (Miller, 1987) is not constant. Externally the true geese strongly resemble several genera assigned to the sheldrake tribe by Delac6ur and Mayr (1945). A number of carpometacarpal features support the allocation of these superficially gooselike species of the genera Chlogphaga, Neochen, and Alopochen to a position near the sheldrakes Tadorna and Casarca, as well as nearer the other duck genera. The following four characteristics of true geese serve to separate them from the sheldrakes: (1) The ex- ternal rim. of the carpal trochIea has the upper poftion extending proxi- mally before curving downward. (2) The external rim of the carpal trochlea is shallowly notched below. In sheldrakes the notch is notice- ably deeper, as js generally true of all ducks. (3) The internal rim of the carpal trochlea is less rounded and usually grades more smoothly into the ridge of hone lying distal to it. In sheldrakes the more. round- 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 25 ed fim falls off sharply. (4) The process of metacarpal I in lateral view is lower; the height through the process ranges from 19.7 to 24.4 per- cent of the total length of the carpometacarpus. In sheldrakes the pro- · cess is typically higher (23.8 to 28.6 percent), a feature that Miller (1937) uses to separate Chlogphaga, from the North American genera of true geese. The process of metacarpal I frequently has a rugose cap in both geese and sheldrakes. Shufeldt (1892) attributes this condition to dis- ease; Miller (1937) thinks its frequency of occurrence makes a patho- logical origin unlikely. Many waterfowl commonly fight with their Wings, and the occurrence of the knob may well be correlated with this behavior. Chlo6phaga, Alopochen, and Neochen almost always have the knob, and all are listed as very quarrels6me by Delacour and Mayr, Caps also occur on the carpometacarpi of Cygnus, Chenopis, Branta, Anser, Tachyeres (large), Hymenolaimus (large), Merganetta (large), and Sarkidiornis. Two genera, Merganetta and Plectropterus, have developed carpal spurs (Rand, 1954), and the latter is known to be aggressive in captiv- ity. In addition to a metacarpal I process seemingly designed for a spur, one specimen of Merganetta, labelled a juivenile male (U.S.N.M. 846808) possesses a sharp claw 8 mm. in length on the tip of the pollex,' a fact apparently unrecorded in the literature (Fisher, 1940). ANATINAE The Anatinae can be distinguished from the Anserahatinae and Anserinae by two carpometacarpal features: (1) The upper surface of metacatpal II is r6unded, without sharp angles. (2) The extensor attachment on the tip of the process of metacarpal I.is longer and ex- tends distally onto the anterior edge of the process (a weak character for sheldrakes). With the ducks the most critical region of the carpometacarpus is the external surface of the trochlea. The shape and location of the attach- ments for two ligaments and the ridges on the bone associated there- with are particularly significant Howard (1929) labels an external lig- amental attachment on her drawings. In waterfowl the ligament at- tached theron extends to the Culieiform (ulnare). Another place of liga- mental attachment from which a ligament extends to the scapholunar (radiale) lies distal to the one labelled in Howard. The external scapho- lunar ligament crosses over the external cuneifdrm ligament. Delaeour (1954, 1956, 1959) divides the Anatinae into seven tribes. Features of the carpometacarpus separate the subfamily into five groups: (1) sheldrakes, (2) dabbling and perching ducks, (8) pochards, 26 BULLETIN FLORIDA STATE MUSEUM Vol. 6 (4) eiders and sea ducks, and (5) stiff-tailed.ducks. Although the carpo- metacarpi of dabbling and perching ducks (greup 2), pochards (group 8), and eiders and sea ducks (group 4) are very similar, combinations of the characteristics listed at the beginning of each should make pos- sible the proper determination of all specimens, assuming comparative material is available. TRIBE TADORNINI (SHELDRAKES). Sheldrakes have three features of the carpometacarpus that distinguish them from other ducks; all three fea- tures are common to the true geese, perhaps an indication of an in- termediate position Of the. sheldrakes between the geese and ducks: (1) The external scapholunar ligamental attachment is ·broad, usually prominent, and situated higher and more distal than in other ducks. It always lies distal to the ridge that extends from the external cuneiform ligamental attachment to the proximal fornix (the point of fusion of metacarpal II and III proximally). (2) The lobe at the distal end of the external rim of the earpal trochlea is larger. (3) The process of metacarpal I is higher, shorter, and frequently has a rugose cap. The carpometacarpus of Cereo'pals resembles those of the Anserini of Delaeour and Mayr (1945). Two unique features distinguish the species: (1) In the process of metacarpal I the proximal edge slopes forward, and the distal edge is more concave so that the tip is more pointed. (2) The distal metacarpal symphysis is approximately twice as. long as that found in geese. With Cereopsis removed because of its resemblance to the true geese, three major groups remain within the sheldrakes: Chloaphaga, Alopochen, and Neochen form one group; Tadorna and Casarca an- other; and Tachyeres the third. No qualitative features separating Casarca from Tadorna are evi- dent, but the two as a unit can be distinguished from Chlodphaga, Alopochen, and Neochen by a combination of characteristics: (1) The process of metacarpal I is lower, thinner in proximal view, nearly perpendicular 'to the shaft, and usually without a rugose cap. In the other three genera the process is higher, thicker, bent proximally, and frequently it possesses a rugose cap. (2) The cuneiform fossa is longer and extends proximally beyond the lobe that marks the distal extent of the external rim of the carpal trochlea. In the others the fossa ends rather abruptly a't a point opposite the lobe. (3) The tuberosity of metacarpal II is more prominent in dorsal view, and does not rise so high up from the shaft in the three gooselike genera. (4) The facet for digit III falls decidedly short of the facet for digit II. In the other three genera the two facets are almost equal in distal extent. 1961 WOOLFENDEN: OSTEOLOGY, OF WATERFOWL 27 Alopochen seems the most distinct of the three gooselike genera. The following features set it apart from the other two: (1) The external surface situated below the external cuneiform ligamental attachment is deeply grooved. (2) The anterior carpal fbssa is shallow. In Chlog- phaga and Neochen the anterior carpal f6ssa forms an obvi6us pit at the edge of the carpal trochlea. (8) The flexor attachment is more dis- tal. In the other two genera the fiexor attachment lies farther prbiti- mad. A ratio of the distance to the midpoint of the f[exor attachment from the proximal end divided by the carpometacarpal length ranges from 27.5 to 30.8 percent with only 1 specimen of 8 having a greater percentage than 29.3. The same ratio ranges from 29.5 to 81.4 in 8 specimens of Alopochen. Although the 8 genera of gooselike sheldrakes are very similar, Neochen seems slightly closer to Chlo6phaga. The f[exor attachment ratio is 28.6 percent for the one specimen, and the ariterior carpal fossa is deep. The groove below the external cuneiform ligamentai attach- ment, however, seems deeper than in most specimens of Chlogphaga Delacour (1954) includes Tachyeres in the sheldrakes, but it dif- fers from that tribe in two diaghostic features Of the catpometacarpus: (1) The external scapholunar ligamental attachment lies on the diago- nal ridge that passes from the external cuneiform ligamental attach- ment to the proximal fornix. In sheldrakes the attachment lies distal to the ridge. (2) The lobe at the distal end of the external rim of the carpal trochlea is essentially lacking. All true sheldrakes have a prom- inent lobe. In Tachyeres the process of metacarpal I is long as in most ducks. The process appears high, as in sheldrakes, but this may be due to foreshoftening of the element; correlated with. a Bightless con- dition. Although a rugose cap is- present as is typical of sheldrakes, this condition is found sporadically throughout the Ariatidae. TRIBES ANATINI AND CAIRININI (DABBLING AND PERCHING DUCKS), (1) The distal portion of the external rim of the carpal trochlea has a noticeable prominence, but it is usually smaller than that found in eiders and sea ducks. The lateral outline of the area is convex. (2) The cune- iform fossa is deeper than in pochards, but us'ually shallower than in eiders and sea ducks. (3) The external scapholunar ligamental attach- ment is prominent and larger than in pochards, and usually lies On a conspicuous ridge that extends from the external cuneiform ligamental attachment to the proximal fornix. (4) The flexor attachment extends distally beyond the proximal fornix. The extent of the proximal end of the flexor attachment is variable. (5) The pro2ess of metacarpal I is higher and straighter than in eiders and sea ducks., 28 BULLETIN FLORIDA STATE MUSEUM Vol. 6 TRIBE ANATINI (DABBLING DUCKS). Features of the carpometacarpus, - do not support the recognition of Chaulelasmus, Mareca, and Spatula as distinct genera. Some differences do occur, but none was found that has a high constancy. Many characters that appear useful in a small series break down when additional specimens are compared. In com- paring 16 specimens of Mareca with 7 of Chaulelasmus, 5 of Spatula, and Over 40 of numerous species of Anas, Mareca proved the most dis- tinct of the three, some specimens being assignable without compara- tive study. The straight, robust shaft and the recessed condition of the facet for digit III are the best. criteria. However, not all the speci- mens could be identified, even with the aid of comparative material. Wetmore (1944) and Brodkorb (1958a) mention that the carpomet- acarpus 6f Anas (Nettion) carolinensis can be sep~arated from that of Anas (Querquedula) discors as follows: (1) Nettion has the anterior carpal fossa very shallow, whereas it is deeply excavated in Querque- dula. (2) In Nettion the length of the distal metacarpal symphysis is 6.0 mm. or less, whereas in Querquedula it is approximately 7 mm. or more. The feature pertaining to the depth of the anterior carpal fossa readily separates 17 of 25 specimens (Nettion 9, Querquedula discors 10, Q. cyanoptera 8, Q. quequedula 8), but for 3 (Nettion 2, Q. discors 1) the character is reversed, and in 5 others it appears intermediate. Just how Wetmore measured the distal metacarpal symphysis is un- certain, but some of the available specimens of Querquedula apparently measure less than. 7 mm:, so,even this character is not entirely constant. Qualitative features of the carpometacarpus indicate that 4 of the. available genera of dabbling ducks are distinct from Anas, namely Callonetta, Malacorhynchus, Hymenolaimus, and Merganetta. Callonetta has three distinctive features: (1) The process of meta- carpal I has its. distal edge sloping sharply proximally, and has only a small attachment surface at the tip. (2) The base of metacarpal III is narrower in ventral view. (8) The external rim of the carpal trochlea is slightly longer and narrower. Malacorhunchus also has three criteria that distinguish it from typi- cal dabblers: (1) The process of metacarpal I appears decidedly shorter in lateral view and has only a small extensor surface. (2) The proximal end of metacarpal III is very narrow and does not extend laterally around the cuneiform fossa. (8) The shaft of metacarpal II is notice- ably thinner in dorsal View . Hymenolaimus is very different from other dabbling ducks: (1) The internal rim of the carpal trochlea is enlarged; it curves farther down- ward and is thicker. (2) The groove between the rims of the carpal trochlea and the cuneiform fossa is very deep. (3) The external scapho- 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 29 lunar ligamental attachment is larger and situated farther distally. In this respect Humenolaimus resembles the sheldrakes. (4) The external portion of the proximal end of metacarpal III fuses with metacarpal II farther distad. (5) The tuberosity of metacarpal II is reduced. (6) The facet f6r digit III is enlarged with the lateral end bent downward and both, ends extended distally. (7) A rugose knob is present on the pro- cess of metacarpal I. Although present in many distantly related water- fowl, a knob is mosttypical of the sheldrakes. The very short carpometacarpus of Merganetta resembles that Of Hymenolaimus in a number of features. As both are inhabitants of mountain streams, convergence of some features might be expected The fbllowing,characteristics distinguish Merganetta: (1) Both rims of the carpal trochlea are enlarged, and especially the internal one; they curve farther downward, and the internal rim is thickened. (2) The groove between the rims of the carpal trochlea and the cuneiform fossa is very deep. (3) The proximal end of metacarpal III is narrower and does not extend so far laterad. (4) The tuberosity of metacarpal II is greatly reduced. (5) The facet for digit II has the external edge more rounded. (6) The facet for digit III is distally produced. (7) The pro- cess of metacarpal I is larger, curves sharply proximad, and sometimes has a large knob. TRIBE CAIRININI (PERCHING DucKs). The perching ducks are only weak- ly differentiated from the dabblers. Two features of the carpometacar- pus are somewhat useful in sepatatingthe tribes: (1) The external scaph. olunar ligamental attachment tends to be obscure. (2) The process of metacarpal I tends to be higher, shorter, and straighter. Features of the carpometacarpus of Plectropterus indicate the genus is a sheldrake and not a perching duck: (1) The external scapholunar ligamental attachment is situated distal to the ridge that passes from the external cuneiform ligamental attachment to the proximal fornix. This feature is typical of the sheldrakes. (2) The lobe at the distal end of the external rim of the carpal trochlea is large. In ducks other than sheldrakes, the lobe is relatively small or even absent. Although Plectropterus does not have the enlargement of inetacar- pal I typical of the sheldrakes, a process of the scapholunar -(figured in Rand, 1954) serves its quarrelsome nature. On the basis of carpometacarpal features, the two most distinct of the remaining genera are Sarkidiornis and Pteronetta. Cairina, Cheno- netta, Aix, and Dendronessa are all very similar to one another. Sarkidiornis can be characterized as follows: (1) Metacarpal I is located farther distad with the highest point of its process opposite the 80 BULLETIN FLORIDA STATE MUSEUM Vol. 6 pisiform ,process. In other perchers the peak is proximal to the pisi- form, and the anterior carpal fossa is more extensive. (2) The external rim of the carpal trochlea is rounded proximally. In the others the rim tends to be acuminate, the point occurring immediately proximal to the ekternal cuneiform ligamental attachment. (3) The groove on the ex- ternal surface below the external cuneiform likamental attachment is deeper. Pteronetta is rather easily distinguished from other perching ducks, including Cairina: (1) The process of metacarpal I is higher. (2) The eurve of the internal rim of the carpal trochlea is situated so that the lowest point underlies the pisiform process, whereas in the others the lowest point is more proximal. The large, robust carpometacarpus of Cairina has one. distinctive fea- ture: The process of metacarpal I is slightly excavated by a depression that lies along the external edge of the base. No qualitative features useful in distinguishing Aix, Dendronessa and Chenonetta were found. Nettapus and Cheniscus, for which I End no mutually exclusive characteristics, differ from other perching ducklin the following way: (1) The prominence proximal to the external cuneiform ligamental at- tachment is higher and extends proximally to the posterior rim. In other perchers it is lower and it terminates distal to the proximal rim. Features of the carpometacarpus of Amazonetta strongly support its recognition as a genus distinct from Anas. The process of metacar- pal I is higher and straighter, a feature characteristic of the perching ducks. In addition, the external rim of the carpal. trochlea appears longer and narrower than in Anas. Separating Amazonetta from other perchers; and. the dabblers, is the facet for digit III that is reduced in size and recessed; :thhs it does not extend distally as far as the facet for digit II. TRIBE A¥THINI (POCHARDS). The carpometacarpus of pochards is quite distiact with the following characteristics: (1) The distal portion of the external rim of the carpal trochlea is usually without a swelling, and generally so greatly reduced that the outline in lateral view is con- cave. (2) The cuneiform fossa is shallow. (8) The external scapho- lunar ligamental attachment is usually prominent, but small. The diagonal ridge from the external cuneiform ligamental attachment to the proximal fornix is usually obscure. (4) The flexor attachment al- ways lies entirely proximal to the proximal fornix. (5) The process of metacarpal I is high and straight as in the dabblers. 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 81 Metopiana and Netta are near Aythya, especially as indicated by the position of the flexor attachment, but certain features of the carpomet- acarpus indicate an intermediate positian between Authya and the dabblers: (1) The bone is shorter and more robust than in Authya (2) The process of metacarpal I is straighter. In Aythya the process curves more proximad. (3) The distal portion of the external rim of the carpal trochlea is more prominent. The area is more reduced in Aythya. (4) The region on the external surface, situated proximal to the external cuneiform ligamental attachment, is larger. In Aythya this area is much reduced. The carpometacarpi of Metopiana and Netta are very similar, but most individuals can be separated by the tubefosity of metacarpal II and the external rim of the facet for digit II which, in dorsal view, are produced farther laterally in Metopiana than in Netta. It is unfortunate that no carpometacarpus of Rhodonessa is available because its humeral features indicate this genus belongs with the pochards and not with tlie dabblers. TRIBES SOMATERIINI AND MERGINI (EIDERS AND SEA DucKS). Eiders and sea ducks form a group easily distinguished from the pochards. The two as a unit seem more like the dabblers, and particularly the perch- ers, in carpometacarpal features. The followin'g distinguishing char- acteristics were noted: (1) The distal portion of the external rim of the carpal trochlea has a prominent swelling that is usually larger than in dabblers and perchefs. (2) The cuneiform fossa is deeper than in the - other groups, and it frequently excavates under or around the internal rim of the carpal trochlea. (8) The external scapholunar ligamental attachment is obscure, and the diagonal ridge "is frequently absent. (4) Thi flexor attachment is variable with the genera. (5) The process of' metacarpal I is lower, wider, and curved proximally. This feature is not useful for separating Bucephala, Lophodytes, or Mergellus, but is extremely useful for the other genera. Examination 6f the carpometacarpi of 70 specimens of eiders and sea ducks reveals two basic facts: (1) The eiders show greater similar- ity to the sea ducks, and particularly to the scoters and Histrionicus, than to the dabblers; (2) the most obvious division of the genera is into two units, one containing Bucephala and the mergansers, the other the eiders, scoters, Histrionicus, and Clangula. This same division is also evident from features of the humerus. The important features for separating the two units are found in the process of metacarpal I, and in the position and shafe of the pollical facet. In Bucephala and the mergansers the process tends to be higher, 32 BULLETIN FL0RIDA STATE MUSEUM Vol. 6 and the extensor attachment on the tip is shorter, In the other group of genera the process is lower, longer in lateral view, and the extensor attachment extends down the sloping distal edge of the process. These features are most distinct in Bucephala, Lophodytes, and Mergellus at one extreme, and Clangula at the other. Some specimens of Mergus are very similar to certain scciters and eiders, but in Bucephala and the mergansers the pollical facet lies in line with Or proximal to the internal rim of the carpal trochlea. In the other genera the pollical facet lies distal to the internal rim of the carpal trochlea. Furthermore, Buce- phala and the mergansers have only a small lateral lobe on the pollical facet, best compared in proximal view. In the other genera the lobe is larger and has a prominent pit or groove between it and the shaft of metacarpal II. These characteristics permit 100 percent separation between Bucephala and the mergansers and the remaining sea ducks. With some features the division within the Bucephala and mergan- ser group appears to lie between Bucephala and the mergansers, but with others the break occurs between Mergus and the other three gen- era. This is the case with humeral features, which indicates that Buce- phala and the mergansers have been previously placed in separate taxa only because of such plastic features as the shape of the bill. A basic difference in the shape of the process of metacarpal I di- vides the sea ducks into two groups. One of these groups, Bucephala and the mergansers, shows significant differences in the relative height of the process. In 18 specimens of Bucephala, Lophodytes, and Mer- gellus the range for the height through the process of metacarpal I is 22.5 to 23.9 percent of the total length of the bone. In 19 specimens 6f Mergus (17 M. serrator, 2 M. merganser) the range is from 21.0 to 22.6 percent, except for one adult M. serrator which measures 17 .9 percent. Only one individual of the latter group overlaps the minimum for the other genera. Of the 17 available specimens of M. serrator, 14 are from Florida and all are immature birds.- It seems likely from comparison with adult birds that the ratio would be more significant if the sample were not biased in respect to age. The small size of the lobe at the distal end of the carpal trochlea separates Bucephala from the mergansers. In Lophodytes, Mergellus, and Mergus the lobe is relatively large. An additional feature useful for separating Bucephala from Mel'gus is the structure of the pisiform process. In proximal View it curves sharply upward in Bucephala, forming a deep groove for the flexor digitorum profundus. In Mergus the pisiform process is directed medially, forming more of a shelf than a groove. Specimens of Lophodytes and Mergellus are intermediate for thii feature. 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 88 With Mergus distinguished by the relatiye height of the process of metacarpal I, the best characters for separating Bucephala from Lopho- dytes and Mergellzd are: (1) the feature pertaining to the external rim of the carpal trochlea mentioned above, and (2) the shape of the facet for digit II. In Bucephah the external portion of the facet for digit II is larger and extends farther down into the groove between the facets for digits II and III. In Lophodytes and Mergellus it is smaller and does not extend down as far. No valid feature for separating Mer- gellus from Lophodytes was found 6n the carpometacarpus. Of the remaining members of the eider and sea duck group, Clangula seems the most distinct. It has the.following characteristics: (1) The process of metacar~al I is very low, with the distal edge thick and curving sharply preximally. (2) The carpal trochlea is depressed; its external rim forms only a slight angle with the trend of the shaft; the internal rim has only a relatively small depression between it and the base of metacarpal III. (8) The pit distal to and below the pisiform process is very deep. (4) The tuberosity of metacarpal II is situated more medially, and as a result the external edge of the facet for digit II appears more rounded. (5) The shaft of metacarpal II is robust (7.8 to 8.8 percent of the total length). The range for the others is 6.5 to 7.9, except for Histrionicus which measures 8.0 percent Two characteristics of the eiders separate them from the scoters and Histrionicus: (1) The flexor attachment is nearly twice as 16ng as in the others, and. is situated fafther distad. (2) The upper surface of the shaft of metacarpal II in.medial view is arched. The carpometacarpus of Lampronetta appears indistinguishable from that of Somateria, but Pdlysticta differs from both in: (1) The notch in the external rim of the carpal trochlea is smaller in ventral view. (2) The 16be immediately distal to the notch is smaller. (3) The cuneiform fossa is shallower. The carpometacarpus of Oidemia is slimmer than that of Melanitta (width of metacarpal II relative to the total length 6.5 to 7.1 percent in Oidemia, 7.0 to 7.9 percent in Melanitta), but otherwise it appears indistinguishable from that genus. Histrionicus has a thick shaft of metacarpal II (8.0 percent of the total length), and a larger lobe at the distal end of the external rim of the carpal trochlea. TRIBE OXYURINI (STIFF-TAIL* DUCKS). The stiff-tailed ducks are the easiest of the Anatinae to deEne on the basis Of the carpometacarpus: (1) The distal margin of the internal rim of the earpal trochlea appears nearly parallel to the shaft in ventral view. In the Others the rim is deflected laterally. (2) Metaearpal III is narrower at the proximal end. 84 BULLETIN FLORIDA STATE MUSEUM Vol. 6 In members of the other four groups metacarpal III widens at the prox- imal end and thus reaches, or virtually reaches, the external side of the element. (3) The area on the external surface below the external liga- mental attachments is deeply grooved. Although a groove is present in other ducks it is not nearly as deep. (4) The facet for digit II is nar- row, crescent-shaped, and has the lower margin concave (Heteronetta is an exception). In the other ducks the facet is broader, and the lower margin is nearly straight. Features of the carpometacarpus strongly support the close rela- tionship of Heteronetta, Nomonyx, Oxgura, and Biziura pointed Out by Delacour and Mayr (1945). Heteronetta is the least specialized mem- ber of the tribe. The features that separate it from the other stiff-tails are generally those found in ducks of other tribes: (1) The process of metacarpal I is higher, and in lateral view, noticeably narrower. (2) The distal margin of the internal rim of the carpal trochlea is defiected laterally in ventral view. In other stiff-tails the process is nearly paral- lel to the shaft; in other tribes it is' even more def[ected than in Heter- onetta. (3) The facet for digit II is broadly rounded externally and has the lower margin straight. (4) The tuberosity of metacarpal II is smaller. (5) The prominence on the internal edge at the proximal end of metacarpal IiI is situated nearer to the proximal fornix. In other stiff-tails it lies more proximad. Nomonyx resembles Oxyum less than itt does Biziura in features of the carpometacarpus. It can be separated from these two genera by the following featurds, all of which seem to indicate a lesser degree of specialization: (1) The process of metacarpal I is noticeably narrower in lateral, view. (2) The distaI margin of the internal rim of the carpal trochlea in ventral view has a slight lateral def[ection greater than that found in Oxyum and Biziura but less than in Heteronetta. (3) The tuberosity of metacarpal II is smaller. (4) The external rim of the carpal trochlea is not as deeply grooved as in other stiff-tails. The following carpometacarpal features separate Biziura from Oxgura: (1) The external rim of the carpal trochlea is extremely deep- ly grooved, more so than in all other anatids, so that the bottom of the , cuneiform fossa can be seen in lateral view. (2) The distal portion of the internal rim of the carpal trochlea is thickened. In Oxyura the rim is of uniform thickness throughout. (3) The tuberosity of metacarpal II curves more laterad. Sternum The sternum has received an exaggerated amount of attention from avian taxonomists. It is not as useful as the humerus, carpometacarpus, 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 85 4,: : I1 1.~- ~-~\ j I 1-- ) Et .. _®ff 4 .. .1. b .../; .am v i 4 1fn 9. J .1 1, b le UIL- -~ a 1 1 A F Ii ,-~ 0 N 1r 2-J- .-- FIGURE 8 . Sternum, dorsal view . Top row : Anseranas semipalmata, Dendrocugna auttimnalis, Cygnus olor, Branta canadensis. Middle row: Cereolisis n.hollandiae, Alopochen aegyptiaca, Anas fulvigilla, Mel·ganetta armata. Bottom row: Agthya ca/:sineria, Clangula hue,nalis, Ox!/ura lamaicensis. 36 BULLETIN FLORIDA STATE MUSEUM Vol. 6 or coraceid; however, some features of phylogenetic significance do occur. Certain structural features of the sternum and pectural girdle may be better understood by reference to the ligaments described in the Appendix. The posterior margin of the sternum 'varies considerably. Most Anatidae have sternal notches, but in a few genera the n6tches are characteristically ossified posteriorly to form fenestrae. Other genera may, on Occasions, have one or both notches so enclosed. ANSERANANNAE The primitive Anseranas is easily distinguished from all other anatids by the following criteria, the first Bve of whieh are unique among the waterfowl: (1) The costal margin is over 50 percent of the length of the basin (measured from the dorsal sulcal lip to the postpectoral line). , (2) The sternal basin is deep. (8) The dorsal surface of the sternal plate ' is pierced by numerous foramina and crossed by transverse ridges. (4) The sternum is trilobed posteriorly, because of very shallow sternal notches and a rounded xiphisternum. (5) A stout median bar extends from the dorsaI sulcal lip into the basin. (6) The dorsal and ventral manubrial spines are lacking. ANSERINAE The Anserinae can be distinguished from the Anseranatinae in the fol- lowing ways: (1) The costal margin is shorter, always less than 50 per- cent of the basin length. (2) The sternal basin is shallower. (8) The pneumatic foramina are confined to the area posterior and ventral to the dorsal sulcal lip, and to the anterior median portion of the basin. (4) The xiphisternum Hares laterally; its posterior margin is truncate or slightly concave, and the sternal notches are deeper. (5) There is no stout bar as described for Anseranas. The Anserinae can be distinguished from the Anatinae as follows: The dorsal sulcal lip overhangs the sternal basin medially, and forms a large concavity at the anteriof end of the sternal plate. The over- hanging lip and the rather prominent costal margins cause the sternal basin to appear deeper. This character is least developed in Nesochen. TRIBE DENDROCYGNINI (WHISTLING DUCKS). The sternum of whistling ducks shares the greatest number of similarities with that of the pied goose. The costal margin is almost as long as in Anseranas, the sternal basin is almost as deap, and the manubrial spines are lacking. Den- drocygna differs from Anseranas in the characteristics listed for the Anserinae; numbers 1, 4,and 5 are particularly useful. The whistling 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 87 ducks can be distinguished from the swans and geese by their lack of a ventral manubrial spine. TRIBE ANSERINI (SWANS AND GEESE). Swans and geese can be separat- ed.into two very distinct units on the basis Of the ster-num. Swans and Coscoroba form One group, and geese form the other. The sterna of these two units are so different as to suggest they might be treated as separate tribes. The sternum of swans is unique in the position of the intermuscular line delimiting the supracoracoideus from the pectoralis superficialis as noted by Stejneger (1882). In swans the line extendi along the sternal plate only a short distanbe, usually less than 75 percent of the carinal length, before it curves down onto the carina. In all other waterfowl the ·intermuscular line extends along the plate essentially to the poster- ior end of the carina. The reduction in the relative length of the line is indieative of the reduction of the supracoracoideus muscle. Further indication of a reduction in this muscle is apparent when the sternum is viewed in ventral aspect. In swans the intermuscular line angles sharply toward the carina; in geese the line essentially parallels the carina throughout its length. The supracoracoideus functions to raise the wing. In the Catharti- dae, Fisher (1946) associates a reduced supracoracoideus with a de- crease in speed of wing flapping. It seems likely that the same princi- ple applies to the swans, which also have a slow wing beat. The swans are further distinguished as follows: (1) The sternal notches are shallow. (2) The posterior lateral processes rarely extend beyond the *iphisternum. (3) The posterior lateral processes are near- ly in a line with the costal margin. (4) The costal margin is elongate, , forming from 40 to 50 percent of the basin length. (5) A ventral man- ubrial spine is present which serves to distinguish swans from Anseranas and Dendrocygna. (6) A pit is present in the dorsal portion of the anterior carinal margin in some specimens of all species. In Olor columbianu&, 0. buccinator, 0. cygnus, and 0. bewickii the pit becomes a huge cavern for a loop of the· trachea. In Cygnus olor, C. melan- coriphus, akid Chenopis·the pit is small or absent, and does not contain the trachea. Only one feature of the sternum, additional to the cavern for the tracheal loop, supports the recognition of Olor as distinct from Cygnus, and this may be a result of widening of the carina in Olor. The pos- terior portion of the pectoralis superficialis lies close to the carina in Cygnus, but far laterad to the carina in Olor, 88 BULLETIN FLORIDA STATE MUSEUM Vol. 6 The sternum of Coscoroba indicates it is closely related to the · swans. The intermuscular line, although more extensive than in the , true swans, curves down onto the carina well anterior to its posterior termination. In ventral view the line gives additional indication of a reduction of the supracoraceideus by distinctly angling toward the carina throughout its length as shown in 'Stejileger (1882). Further evidence for considering Coscoroba near the swans comes from the fact that some specimens possess a pit in the dorsal portion of the ca- rinal margin. Coscoroba can be distinguished from the true swans by the following criteria: (1) The intermuscular line extends beyond 75 percent of the carinal length (usually about 90 percent). (2) The pos- terior lateral processes extend well beyond the xiphisternum. Both features are figured in Stejneger (1882). Of all the Anserinae, the true geese are closest to the Anatinae. , Geese may be distinguished from Anseranas and other Anserinae by: (1) The costal margin is less extensive (usually less than 40 percent of the basin length). (2) The sternal notches are deeper (more than 88 percent of the basin length). (8) The posterior lateral processes flare from the costal margins. (4) The xiphisternum is normally widened posteriorly. (5) A dorsal manubrial spine is present. In other Anser- inae and in Anseranas the notch is enlarged and eliminates the spine. These characters, except the last, are also present in the Anatinae. The sterna of geese show little ,generic variation. Miller (1987) in his comparison of Nesochen with Branta, Anser, Chen and Philacte found several features to distinguish Nesochen, but no constant char- acters to separate the remaining fQur genera. from one another. Nesochen is characterized by the following features: (1) The ster- num is narrower, the width (narrowest e*tent between the costal mar- gins) varying from 67 to 40 percent of the basin length. In all other geese the minimum is over 41 percent. (2) The carina is visibly lower. As Miller states, the difference in carinal height is evident only posterior to the apex where no fixed points for measurements can be selected. (8) The ventral manubrial spine is a transverse ridge less thick than the buttonlike prominence of other genera. (4) The pneumatic foramen is very small, less than a millimeter wide. (5) In addition to these fea- tures, which have been verified in the present series, the one available Nesochen has a less prominent intermuscular line, especially posterior- ly. Possibly all of the above features, and certainly 1, 2, and 5, can be attributed to eurtailed Hight. One character that . allows the separation of Branta from Anser, Chen, Philacte, and Nesochen is the shape of the ventral manubrial spine. In Branta the spine is compressed into a vertically spatulate 1961 WOOLFENDEN: OSTE0LOGY OF WATERFOWL 89 process, whereas in the other four it is of the normal peglike shape. Tiko specimens of Cygnopsis and One of.Eulabeia are intermediate in this .respect. ANA#NAE In the ducks the sternal basin is distinctively Hattened. The reduced posterior surface of the dorsal sulcal lip and the less prominent costal margins eliminate the large concavity at the anterioY end of the sternal plate. Miller found this character the best means of distinguishing Cm06phaga, here considered in the Anatinae, from the true geese. All the duck tribes cannot be separated by sternal chatacters alone, but a number of sternal features aid in distinguishing 'some tribes or parts of tribes. For those tribes that cannot 'be characterized by the sternum alone, the various genera are discussed under the tribal units of Delacour (1954, 1956, 1959). Similarities to gentra in other tribes are mentioned. TRIBE TADORINI (SHE:LDRAKES). Within the Anatinae the sheldrakes are most like the true geese in features of the sternum, particularly in the rather prominent dorsal sulcal lip and the numerous pneumatic fora- mina in the sternal basin. In addition to lacking a distinct concavity beneath the dorsal suleal lip, the sheldrakes may be separated from the closely 5imilar true ge~ese as follows: 01) the costal facets number six or less, except in the aberrant Cereopsis and Tachyeres (in geese a minimum of seven is present). (2) The costal margin typically tapers Do#enorly. The sternum of sheldrakes is narrowest immediately ad- jacent to the last costal process; whereas in geese the narrowest point, which is sometimes difficult to establish, always lies anterior to at least two costal processes. The difference is undoubtedly a manif6sta- tion of the above characteristics. Milier uses the shape of the sterno-coracoidal process to aid in separating Chlo*haga from the true geese; in Chlo6phaga it is longer and projects more anteriorly. Although the process is variable, the differences between Chlo6phaga and true geese are generally those be- tween Anatinae and Anserinae, and therefore it serves t6 Separate the two subfamilies. Miller's other criterion for separating ChloLphaga from the true geese is the relative length of the posterior lateral pro- cesses, extending well beyond the xiphisternum. As a few goose speci- mens show the same feature, this character is not infallible. The sheldrakes form a fairly distinct tribe. The stifnal basin is deeper than in other ducks, although there is overlap with some dab- blers and perchers. The shape of the pneumatic fossa is also of limited 40 BULLETIN FLORIDA STATE MUSEUM VoI. 6 use. The fossa is typically a large opening bordered laterally by stout bars, which frequently are fused with the sternal plate. The resulting fossa does not have the rouiid or eliptical shape of other ducks, but instead it is a constricted opening that is either oval or somewhat rec- tangular in outline. The sterno-coracoidal process is shorter and has a more prominent posterior extension in the sheldrakes than in other ducks. Tachyeres differs strongly from other sheldrakes in its broad, flat sternum. (1) The width is 55.6 percent of the basin length. (2) The ventral manubrial spine barely protudes beyond the ventral sulcal lip. (3) The carina is greatly reduced, with the posterior two-thirds of its margin virtually a straight line. (4) The posterior lateral process curves mediad more than in other sheldrakes. (5) The pneumatic fossa is ellip- tical and small. (6) The stern6-coracoidal process is longer and lacks a prominent posterior extension. The very shallow basin, ducklike sterno-coracoidal process, pos-sibly the elliptical fossa, and the seven costal processes suggest that Tachyeres may be incorrectly located in the sheldrake tribe. Characteristics of the sternum of Cereopsis disclose little more than the fact that.it is aberrant. The element has qualities of both the shel- drakes and the true geese. The following features were noted: (1) The sternal basin is deeper than in sheldrakes, but lacks the concavity beneath the dorsal sulcal lip found in geese. (2) The dorsal manubrial area is notched as in many sheldrakes, whereas no geese.have a distinct noteh. (8) The ventral manubrial spine is lacking. All geese have such a spine, as do most sheldrakes. (4) The xiphistefnum is not flared. pos- teri6rly as is true of all sheldrdkes and most geese. (5) The costal processes number 6 or 7; a minimum of 7 was counted f6r geese, a maximum Of 6 for sheldrakes, Tathyeres excluded. (6) The carinal margin is more curved throughout its length than in members of either of the two tribes. Among the m6re typical sheldrakes, ChloKphaga has the widest sternum (46.9 to 50.8 percent of. basin length), Tadorna and Casarca the narrowest (40.1 to 45.1 percent), whereas Alopochen (44.9 to 49.8) and Neochen (45.8 to 45.8) are intermediate. Chloaphaga usually has abundant pneumatic foramina; Tadorna and Casarca have onily the large, 66ntrally located one; Alopochen and Neochen are intermediate, but nearer ChloEphaga. In Chlo6phaga, Alopochen and Neochen the posterior lateral processes extend well beyond the xiphisternum. In Tadorna and Casarca, where they are shorter, they normally extelid less than 5 mm. beyond. 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 41 Chlotphaga has a narrower xiphisternum (its least width divided by the least width between costal margins, 31.8 to 44.8 percent) than Alopochen (66. 5 to 66. 9), and Neochen (50.5 to 54. 6), but in Tadorna and Casarca the structure varies greatly in width with the different species. Chloaphaga has a higher carina than Alopochen, and it ex- tends farther back on the sternal plate. Neochen, Tadorna, and Casarca are more like Chloaphaga in this respect. TRIBE AIVATINI (DABBLING D.~CKS). The sternum of dabbling ducks shows the following characteristics: (1) The sternal basin is shallower than in the sheldrakes. (2) The single pneumatic foramen is elliptical or round. (8) The ventral manubrial spine is usually present and typi- cally long, thin, and peglike. (4) The sternum is narrow (Anas, Chaule- lasmus, Mareca, Spatula, 87.5 to 48.9 percent of·total length; Callonetta, 48.8, Malacorhynchus, 44.4, Hymenolaimus, 44.5), narrower than in most members of the four diving-duck tribes. Rhodonessa and Met- ganetta are exceptions: (5) The posteri6r lateral processes are Straight- er than in divers and only occasionally fused with the xiphisternum. Within the tribe the sterna of all genera except Rhodonessa and especially Merganetta are very similar. Callonetta has two weak fea- tures that support generic status: (1) The costal processes number six, whereas the vast majority of specimens of typical dabblers have seven, although the range is from six to eight. (2) The ventral manu- brial spine is thinner, with a weak dorsal area for the ligamental at- tachrrient. Malacorhynchus has the ventral manubrial spine large and strong as in typical dabblers but differs in having six costal processes. Hy- menolaimus is also very similar to the typical dabblers, surprising when one considers its habits. It has the following differences: (1) The costal processes number six. (2) The ventral manubrial spine is re- duced to a weak projection. (3) The dorsal manubrial area has a prominent notch. (4) The carina is slightly reduced with its ventral edge only slightly curved. Rhodonessa can be distinguished at once from the typical dabblers » by several good sternal features: (1) The sternum is wider (50.8 per- cent of basin length). (2) The dorsal manubrial area is notched. (3) The ventral manubrial spine is lacking. The one available specimen (USNM 844802) lacks the spine as apparently did the one used by Verheyen (1955). Though occurring also in certain perching ducks, this feature is generally limited to the species with diving habits, but Rhodonessa does not habitually dive (Delacour, 1956). 42 BULLETIN FLORIDA STATE MUSEUM Vol. 6 * In Merganetta the sternum has the following features: (1) It is wide, 52.7 to 52.9 percent of the basin length. (2) The ventral manu- brial spine is lacking. (8) The carina is greatly reduced, the margin being straighter than in typical dabblers. (4) The posterior lateral processes curve more mediad. (5) The sternal notches are reduced to 44 of the basin length (they measure approximately 43 in other dabbling ducks). (6) The dorsal manubrial area is deeply notched, and has two prominent lateral projections. The sternum of Merganetta diverges from th6Se of typical dabblers to the extent that tribal status for the species may be justified. The sternum of Saluadorina was studied by Mayr (1981), who found the element somewhat narrower than in Anas platyrhynchos, especially caudally, and with the intermuscular line less clearly marked. In sternal characteristics he concluded that Saluadorina is closer to Anas plat!/rhynchos than to A!/th!/a. TRIBE CAIRININI (PERCHING DUCKS). As the sternum of perching ducks does not differ significantly from that of the dabbling ducks, it is im- possible to characterize the tribe as a whole on the basis of this ele- ment. Within the tribe, Cairina, Aix, and Dendronessa have the ventral manubrial spine greatly reduced, whereas in Amazonetta, Chenonetta, Nettapus, and Cheniscus it is prominent. Pteronetta and Sarkidiornis are intermediate in this respect. Cairina has numerous pneumatic foramina beneath the dorsal sulcal lip and costal margins, and along the midline of the basin. In Other perching ducks, with the exception of the aberrant Plectropterus, only the large, anteriorly-and centrally located foramen is present. Plectrop- terus resembles the sheldrakes more closely than the perching ducks in the structure of the sternum: (1) The sternal basin is deeper than in all ducks except certain sheldrakes. (2) The pneumatic foramen is bordered laterally with struts as described for the sheldrakes. (3) The dorsal manubrial area is deeply notched and has the lateral processes found in certain sheldrakes. TRIBE AYTHYINI ing ducks, but not to the extent found in other divefs. (2) The external condyle extends farther distad than the in- ternal condyle as in the nondivers. ( 3) The amount of anterior over- hang of the internal condyle is greater than in the nondivers, but less than in other stiff-tails. (4) The outer cnemial crest is directed more laterad, less anteriorly. In this respect Heteronetta resembles non- diving ducks, and not stiff-tails. (5) .The shaft is thinner (4.1 percent of length) than in other stiff-tails (5.0 to 6.4 percent). Nomonyx appears less specialized for diving than either Oxyura or Biziura. Its tibiotarsus has the following characteristics:· (1) The ex- ternal condyle extends farther distad as in the nondivers and Heteron- etta. (2) The external ligamental prominence is obscure in anterior view. (8) The direction of the outer cnemial crest is intermediate be- tween Heter6netta and the other stiff-tails. (4) The inner cnemial crest lacks the long ridge found in the more specialized genera of the tribe. (5) The shaft width (5.4 percent of length) is similar to that of Oxyura (5.0 to 5.4), thicker than Heteronetta (4.1), and thinner than Biziura (6.4). Oxyum and Biziura share the following features of the tibiotarsus: (1) The distal extent of the two condyles is equal or subequal. (2) The 1961 WOOLEENDEN: OSTE0LOGY OF WATERFOWL 79 , external ligamental prominence is obvious in anterior · view. (8) The outer cnemial crest is directed more anteriorly than in the two less specialized stiff-tails. (4) The inner enemial crest possesses a ridge that extends distally beyond the proximal end of the flbularcrest. Although the tibiotarsi of Biziura.and Oxyura are quite similar, at least three good qualitative characters separate them. (1) In Biziura the shaft'is tbicker, 6.4 percent of the length, as opposed to a maximum ' Of 5.4 percent in the Other genera. (2) In Biziura the shaft,is virtually straight in lateral view. In Oxyum and. Nomonyx a. distinct curvature makes the posterior side concave. (8) In Biziura the proximal edge of the outer chemial crest is virtually a straight line; in Oxgura it is deep- ly concave. Tatsometatarsus The tarsometatarsus is the best taxonomic element of the leg. The - many articulating surfaces partly account for its usefulness. As with other leg b6nes, adaptive modifications frequently Obscure the more basic features. ANSERANATINAE Anseranas has many distinctive tarsometatarsal features: (1) The median calcaneal ridge of the hypotarsus is greatly enlargedZ In all other waterfowl the median ridge is the largest of the four, but it is not proportionately as large as in Anseranas. (2) The facet·for metatar- sal.I is deep and promirient, possibly as a reflection of a stronger hind toe useful foF perching; other waterfowl show virtually no evidence of this facet. (8) The shaft in lateral view is thin. In other waterfowl the shaft is thicker, especially distally. (4) The wing of the trochlea for digit II is gr,eatly enlarged. (5) The trochlea for digit II lacks· a pro- nounced median groove. (6) The external rim of the groove of the trochlea for digit IV is extended posteriorly. ANSERINAE One feature of the tarsometatarsus indicates. a close relationship be- tween the, whistling ducks and the swails and geese. The trocblea for digit II- has a prominent lobe on the anterior side at the point of the most proximal extent of the articulating surface. TRIBE DENDROCYGNINI Sf :% ''~i . 56' A"/0/b " -4 ./ 4- it ./F , i. I.. mrk. 4 1 JL .' '* j, 1 .1/~53, ' 11 1 1 - 34 , I. 111 , - -:" ff~5, f f L*&02 0SI . - -ES' . 9**, - - ''C. - 1* 2 *TER-COR: ,»* , '. 1 , , , i ,-,-1 51fs I 133 - './ 1 ' ' FURS - SQAR DOR, 4»--- : '| 1 C. -27-,i- , ''f--Ill'iV 1 - ~ COR-SCAP. EXT.*=4- E ' ' ' '41 ,/1 f ' 2 5 •1EudirS'GAR 3. ~,0 3, r 1„ ,./'4--96 ir , * COR.%>HARI'll: .,5 „ - 1 .~ toR- FURC . #1 ~ :'* ' ---11 - t..I 45 . . 476.:7. 2 ,/b 41* · k *&&· .4 * ' SY*ERS*'40 668.*/ - 0, - . f 1 + * 74 =S : i M b . i : JI m ' p.&".5 i.*. 4=,I -. 9, STER-COR-CUV." FIGURE 6. LIGAMENTS OF PECTORAL GIRDLE. Anterodorsal view of Anas pendope. Ligaments removed from left side. Membrana sterno-coraco-clavicularis re- moved from right side. Membrana interclavicularis completely removed. cor-caps. Ligamentum coraco-capkulare cor-fure. Ligamentum coraco=furculare con intrin. Ligamentum coracoideum intrinsicum cor-scap. ext. Ligamentum coracoideo-Scapulare externum cor-scap. inf. Ligamentuin caracoideo-scapulare inferius furc-scap. Ligamentum furculo-scapulare furc-scaD, dor. Ligamentum furculo-scapulare dorsale ster-cor. Ligamentum sterno-coracoideum ster-cor-clav: Menibrana sterho-coracd=clavicularis ster-cor. dor. Ligamentum sterno-coracoideum dorsale 124 BULLETIN FLORIDA STATE MUSEUM Vol. 6 APPENDIX: LIGAMENTS OF THE PECTORAL GIRDLE To understand the functional significance of the various processes on the bones of the pectoral girdle, it was necessary to study the ligaments connecting the three elements to each other and to the sternum. Nowhere in the literature are the ligaments in this area concisely explained, and some appear to be un- named, (see fg. 6) MEMBRANA STERNO-CORACO-CLAVICULARIS, Gadow, 1891 Lames latdrales and Lame midiane postdriet,re ou verticale de rappareit dpisternal combined. Harting, 1864, see Gadow, 1891. Ligamentum sterno-furculare. Gadow, 1891 (may be a synonym for only a part of the membrane). Composed of a single posteroventral sheet and a pair of anterolateral sheets. The single ligamentous sheet (Lame m~liane post#rieure) extends posteriorly from a line between the anterior tip 6f the ventral manubrial spine of the sternum and the furcular process of the furculum to the anterior carinal margin of the sternum: In species lacking a prominent spine the extent of the single sheet is reduced. The sheet becomes double (Lames latdrales) as it passes from the tip of the ventral manubrial spine Onto the lateral ridges on the dorsal surface of the spine and from the furcular process Onto the clavicles. Each sheet stretches from the , ventral manubrial spine to the coracoid, where it attaches along the internal , margin, from the midpoint of the shaft to the procoracoid and brachial tuberosity. From the brachial tuberosity the sheet passes to the lateral ridge on the coracoidal tuberosity of the furculum (an anteriorly directed process near the scapular tuberosity) by means of· the anterior portion of Ligamentum coraco-furculare. Thence, it soon passes posterolaterally to the medial side, where it reaches the symphysis of the furculum and joins the sheet from the other clavicle. A ligamentous line on the lateral surface of the sheet extends from the 'inter- muscular line of the carina to the triosseal canal,. to separate M. supra-coracoideus dorsomedially from M. pectoralis ventrolaterally. MEMBRANA INTERCLAVICULARIS Lame mddiane anterieure ou horizontale. Harting, 1864, see Gadow, 1891. Interclavicular membrane. Humphrey, 1958b. A membranous sheet stretching between the arms of the furculum, attaching along the medial edge of the bone from the symphysis almost to the tip of the scapular tuberosity of the furculum whence it extends to the short medial ridge of the acFomion of the scapula and thence to the axial musculature. It is pierced in the middle by the trachea, and more dorsally by the esophagus. The tracheal bulla, when present, lies posterior to this membrane. LIGAMENTUM CORACOIDEO-SCAPULARE EXTERNUM. Cadow, 1891 Attaches the glenoid facets of the coracoid and scapula, respectively, and - forms a U-shaped groove for the head of the humerus. It is very thick. 1961 WOOLFENDEN: OSTEOLOGY OF WATERFOWL 125 , LIGAMENTUM CORACOIDEO-SCAPULARE INFERIUS. Gad6w, 1891 Extends from the riblge on the dorsal edge of the procoracoid and the rim of the scapular facet of the coracoid to the anterior edge of the scapula, It holds the coracoidal articulation of the scapula: in the scapalar facet of the coracoid. LIGAMENTUM CORACO-CAPSULARE. Gadow, 1891 Extends from the brachial tuberdsity of the doracoid to the triosseal ridge on the dorsal surface of. the acromion of the scapula. LIGAMENTUM CORACOIDEUM INTAINSICUM - Connects the procoracoid and the brachial iuberosity of the coracoid. This ligameht and L. coraco-capsulare are very strong and closely parallel each other and Membrana sterno-coraco-clavicularis. The two ligaments seal off the medial side of the triosseal canal In some birds L. coracoideum intrinsicum is osseous. LICAMENTUM STERNb-CORACOIDEUM. Gadow, 1891 Extends from the most anterior rims of the coracoidal sulcus of the sternum to the most anterior ridges 6f the sternal facet of the coracoid. LIGAMENTUM STERNO-CORACOIDEUM DORSALE Extends from the lateral prominence of the dorsal manub~ial area of the sternum to the uppermost scar on the dorsal surface of the coracoid. LIGAMENTUM CORACO-FURCULARE. Gadow, 1891 Extends from the most anterior portion of the brachial tuberosity Qf the coracOid tu the lateral ridge of the scapzilar tuberosity of the furculum, and from the ventral portion of the furcular facet of the corac6id to the coracoidal tuberosity of the furculum. The tissue between these two strengthened Rortions of the ligament is membranous. Membrana sterno-coraco-claviculafis attaches to the latter of the two ligamentous portions desctibed as it passes. from coracoid to furculum. In geese the portion that extends to the coracoidal tuberosity is considerably broadened, and the coracoidal tuberosity forms a ridge instead of a tubercle. LICAMENTUM FURCULO-SCAPULARE. Gadow, 1891 Extends from the posterior surface of' the scapular tuberosity of the furculum to the dorsal surface of the acromion of the scapula. LIGAMENTUM FURCULO-SCAPULARE DORSALE Extends from the extreme tip of the scapular tuberosity of the furculum to the sOmetimes obsture ridge lying unteromediad from the dorsal protuberance (a swelling in the middle of the dorsal surface of the neck) of the scapula. In wateffowl the furcul\Im plainly makes no direct articulation with either of,the other elements of· the pectoral girdle, but instead is held in clbse proximity medially by several strong ligaments. The freedom of movement of the furculum can be detected in fresh specimens, 126 BULLETIN FLORIDA STATE MUSEUM Vol. 6 LITERATURE CITED Ashley, James F. 1941. A study of the structure of the humerus in the Corvidae. Condor, vol. 48, no. 4, pp. 184«195. American Ornitholdgists' Union 1945. Twentieth supplement to the American Ornithologists' Union checklist of North American birds. Auk, vol. 62, no. 8, pp. 486-449. Boetticher, Hans 1943. Die phylogenetisch-systematische Stellung von Anseranas. Zo61. Anz., vol. 142, pp. 55-58. 1952. Ginse und Entenv6gel aus aller Welt. Die Neue Brehm-Bucherei, val. 78, pp. 1-95. Brodkorb, Pierce 1955. The avifauna of the Bone Valley formation. Florida Geol. Surv:, Report Invest., no. 14, pp. 1-57. 1958a. Birds from the middle Pliocene of McKay, Oregon. Condor, vol. 60, no. 4, pp. 252-255. 1958b. Fossil birds from Idaho. Wilson Bull., vol. 70, no. 8, pA 287-242. 1960. The skeleton and systematic position of Gampson!/x. Auk, vol. 77, no. 1, pp. 88-89. IMS]..Birds ·from the Pliocene of Juntura, Oregon. In press, Univ. Oregon Press. Cotter, William B. Jr. 1957. 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Adaptations and comparative anatomy of the locomotor apparatus of new world vultures. Ibid., vol. 35, no. 3, pp. 545-727. Gadow, H ans 1891. V6gel. In H. G. Bronn (ed.), Klassen und Ordnungen des Thier-Reichs. C. F. Winter'sche Verlagshandlung, Leipzigs vol. 6, pt. 4, subpt. 1, pp. 1-1008. 1898. V6gel. Ibid., vol 6, pt. 4, subpt. 2 pp. 1-303. Goodman, Donald C., and Harvey I. Fisher [MS]. Functional anatomy of the feeding apparatus in fvuterfowl. In press, Southern Illinois Univ. Press, Carbondale. Hartert, Ernst 1928. Die V6gel der paliiarktischen Fauna. R. Friedlander & Sohn, Berlin, pp. 1-92. Howard, Hildegarde 1929. The avifauna of the Emeryville shellmound. Univ. California Publ Zool„ vol. 32, no, 2, pp. 801-394. 1946. A review of the Pleistocene birds of Fossil Lake, Oregon. Carnegie Inst. Washington Publ. 551, pp 141-195. Humphrey, Philip S. 1958a. Classification and systematic position of the eiders. Condor, vol. 60, no. 2, pp. 129-135. 1958b. The trachea of the Hawaiian goose. Condor, vol. 60, no. 5, pp. 803- 807. Humphrey, Philip S., and Robert S. Butsch 1958. The anatomy of the Labrador duck, Camptorhync/Mis labradorius (Gmelin). Smithsonian Misc. Coll., vol. 185, no. 7, pp. 1-28. Johnsgard, Paul A. 1960a. Hybridization in the Anatidae and its taxonomic implications. Condor, v61. 62, rio. 1, pp. 25-88. 196Ob. Comparative behaviour of the . Anatidae and its evoluti6nary implica- tions. The 11th Annual ReDort of the Wildfowl Trust 1958-1959, pp. 31-45. F. Bailey &. Son, Ltd., Dursley, Gloucestershire. 1960c. Classification and evolutionary relationships of the sea ducks. Condor, vol. 62, no. 6, pp. 426-483. Lorenz, Konrad [no date]. Comparatibe studies on the behaviour of the Anatinae. Avicultural Society, London, pp. 1-87. 128 BULLETIN FLORIDA STATE MUSEUM Vol. 6 Mayr, Ernst 1981. Zur Anatomie und systematischen Stellung der Salvadori-Ente (Sal- 1>adorina waigiunensis Rotscli. & Hartert). Ornithol. Monatsb,, vol. 39, no. 8, pp. 69-70. Mayr, Ernst, and Dean Amadon 1951. A classification of recent birds: Amer. Mus, Novitates, no. 1496, pp. 1-42. Miller, Alden H. , 1987. Structural modifcations in the Hawaiian goose (Nesochen sanduicensis). A study in adaptive evolution. Univ. California Publ. Zool., vol. 42, no.,1, pp. 1-80. Miller, DeWitt 1919. Notes on the structure of Anseranas semipalmata. Auk, vol. 86, no. 4, pp. 562-564. Moynihan, M. 1958. Notes on the behavior of the flying steamer duck. Auk, vol. 75, no. 2, Pp. 183-202. Newton, Alfred 1896. A dictionary of birds. Adam and Charles Black, London, xii + 1088 pp. Niethammer, G. 1952 . Zur Anatomie und systematischen Stellung der Sturzbach-Ente (Mer- ganettd armata). Jour. fur Ornithol., vol. 93, pp. 857.-860. Parkes, Kenneth C. _ 1955. The generic name of the spectacled eider. Auk, vol. 72, no. 1, pp. 85-86. Peters, James L. 1981. Check-list of ·birds of the worId. Harvard Univ. 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The electrophoretic patterns of avian egg-white proteins as taxonomic characters. Ibis, vol. 102, no. 2, pp. 215-284. Stejneger, 'Leonhard 1882. Outlines of a monograph of the Cygninae. Proc. U.S. Natl. Mus., vol. 5, no. 275, pp. 174-221. 1885. The standard-natural history. Birds. S. E. Casino and Co., Boston, vol. 4, viii + 558 pp. Stettenheim, Peter 1958. Bird fossils from the late Pleistocene of Kansas. Wilson Bull., vol. 70, no. 2, pp. 197-199. Stresemann, Erwin. 1959. The status of avian systematics and its unsolved problems. Auk, vol. 76, no. 8, pp. 269-280. Verheyen, Ren6 1955. La systdmatique des Ans6riformes basde sur l'ostdologie comparde. Bull. Inst. Roy Sci. Nat. Belgique, vol. 81, no. 85, pp. 1-18; no. 86, pp. 1-16; no. 37, pp. 1-22; no. 58, pp. 1-16. Wetmore, Alexander 1924. Fossil birds from southeastern Arizona. Proc. U.S. Natl. Mus.,» v61.. 64, art. 5, pp. 1-18: 1948. An extinct goose from the island of Hawaii. Condor, vol. 45, no. 4, pp, 146-148. 1944. Remains of birds from the Rexroad fauna- of the upper Pliocene of Kansas. Univ. of Kansas Sci. Bull,, vol 80, pt. 1, no, 9, pp 89-105. 1948. A Pleistocene record for Mergus merganser in Illinois. Wilson Bull., vol. 60, no. 4, p. 240: 1951. Observations on the genera of tlie swans. Jour. Washington Acad.'Sci., vol. 41, no. 10, pp. 888-340. 1960. A classification for the birds of the world. Smithsonian Misc. Coll., - vol. 139, no. 11, pp. 1-87. Woolfenden, Glen E.. 1959. A Pleist6cene avifauna from Rock Spring, Florida. Wilson Bull., vol. 71, no. 2, pp. 188-187. Contributions to the BULLETIN OF THE FLORIDA STATE MUSEUM may be in any field of biology. Manuscripts dealing with natural history or systematic problems involving the southeastern United States or the Caribbean area are solicited especially. Manuscripts should be of medium length-50 to 200 pages. Examination for suitability is made by an Editorial Board. 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