BULLETIN
of the

FLORIDA STATE MUSEUM
Biological Sciences

Volume 19 1975 Number 3

THE OSTEOLOGY OF MICROGOBIUS SIGNATUS POEY
(PISCES: GOBIIDAE), WITH COMMENTS

ON OTHER GOBIID FISHES

Ray S. Birdsong

e
UNIVERSITY OF FLORIDA GAINESVILLE



Numbers of the BULLETIN OF THE FLORIDA STATE MUSEUM.
BIOLOGICAL SCIENCES, are published at irregular intervals. Volumes con-

tain about 300 pages and are not necessarily completed in any one cal-
endar year.

CARTER R. GILBERT, Editor

RHODA J. RYBAK, Managing Editor

Consultants for this issue:

ERNEST LACHNER
STANLEY H. WEI'IZMAN

Communications concerning purchase or exchange of the publications
and all manuscripts should be addressed to the Managing Editor of the
Bulletin, Florida State Museum, Museum Road, University of Florida,
Gainesville, Florida 32611.

This public document was promulgated at an annual cost of
$1,629.50 or $1.630 per copy. It makes available to libraries,
scholars, and all interested persons the results of researches in
the natural sciences, emphasizing the Circum-Caribbean region.

Publication date: 28 March 1975 Price: $1.70



THE OSTEOLOGY OF MICAOGOBIUS SIGNATUS POEY
( PISCES: GOBIIDAE),

WITH COMMENTS ON OTHER GOBIID FISHES

RAY S. BIRDSONGl

SYNOPSIS: The osteology of Microgobius signatus is described in detail and com-
pared with other species of Microgobius and with representatives from selected re-
lated genera. Osteological evidence supporting the concept of the American seven-
spined gobies as a natural assemblage is presented, and the group is formally
recognized as the Tribe Gobiosomini of the Family Gobiidae. Osteological character-
istics and trends within the gobioids are discussed, and Miller's classification of the
group is commented upon.

TABLE OF CONTENTS

INTRODUCTTAN 1313
ACKNOWLEDGMENTR 136
METHODS 137
MATERIAL EXAMINED ............._--------------------------------------- 137
OSTEOLOGY OF Microbius st[gnat,of 140

Head Region 140
Pectoral Girdle and Paired Fins 157
Vertebral Column and Median Fins_.............___--_.....__- 159

DISCUSSION 183
Comparison of M. signatus with Other Species of Microgobius 172
Comparison of Microgobius with Related Genera..__...._ 173
Validity of the American Seven-spined Goby Group 180
Comments on Miller's Classification of Gobioids_.........---_.- 182

LITERATURE CrrED 184
KEY TO ABBREVIATIONS 187

1 The author is an Associate Professor of Biology and Oceanography in the Depart-
ment of Biology, Old Dominion University, Norfolk, Virginia 23508. Manuscript
accepted 25 March 1974.

Birdsong, Ray S. 1975. The Osteology of Microgobius signatus Poey (Pisces:
Cobiidae), with Comments on Other Gobiid Fishes, Bull. Florida State Mus.,
Biol. Sci., Vol. 19, No. 3, pp. 135-187.



136 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

INTRODUCTION

In recent years some 20 genera of American Gobiidae with seven
spines in the first dorsal fin have been grouped together as the American
"seven-spined gobies" ( B6hlke and Robins 1968, 1969; B6hlke 1969). The
grouping of these more than 100 species has been based primarily on
external characteristics; however, my study will show that they may
share several distinctive osteological characteristics as well. This new
evidence, combined with the circumscribed geographical distribution of
the seven-spined gobies, adds weight to their recognition as a natural
assemblage.

Bdhlke and Robins· ( 1968, 1969 ) clarified many of the relationships
within the central group of American seven-spined gobies ( i.e., Gobio-
soma and its derived genera). They specifically excluded from the
central group the genera Microgobius and Bollmannia, which they be-
lieved to be only distantly related to the Gobiosonia group, and the genus
Parrella, which they believed to be a composite and too poorly known
to relate. Hoese ( 1971) differed with some of the generic concepts pro-
posed by B6hlke and Robins, but agreed that Microgobius, Bollmannia,
Parrella, and Palatogobius do not appear to be closely related to the
Gobiosoma group. Ginsburg (1939:57) allied Microgobius to Bollman-
nia and stated that Parrella appeared to be intermediate between the two.
More recently, Gilbert ( 1971: 33) allied a new genus, Palatogobius, with
Microgobius and BoUmannia.

This study was undertaken to provide a detailed osteology of a repre-
sentative American seven-spined goby and to attempt to clarify the re-
lationships between Microgobius, Bolbnannia, Parrella, and Palatogobius
and the Gobiosoma group.

ACKNOWLEDGMENTS

I extend thanks to the many people who have rendered assistance during this
study. My special thanks goes to C. Richard Robins of the Rosenstiel School of
Marine and Atmospheric Sciences, University of Miami, for his support and review
of the manuscript.

Ernest A. Lachner, Stanley H. Weitzman, and Victor G. Springer, United States
National Museum of Natural History, have provided valuable discussion, specimens,
and review of the manuscript. Donn E. Rosen and Gareth Nelson, American
Museum of Natural History, gave advice on various points of nomenclature. Thomas
H. Fraser of the United States National Museum of Natural History provided
valuable criticism and suggestions. Other former students at the Rosenstiel School
of Marine and Atmospheric Sciences, University of Miami, who lent valuable assist-
ance in diverse ways are: William P. Davis, William N. Eschmeyer, Alan R. Emery,
Jon C. Staiger, Thomas Devany, David M. Dean, David G. Smith, and Tomio
Iwamoto.

Specimens were loaned by James E. B6hlke, The Academy of Natural Sciences,
Philadelphia; Charles E. Dawson, Gulf €oast Research Laboratory, Ocean Springs,
Mississippi; Carter R. Gilbert, Florida State Museum, University of Florida, Gaines-



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 137

ville; Boyd W. Walker, University of California at Los Angeles; Richard H. Rosen-
blatt, University of California at San Diego; John S. Ramsey, then of the University
of Puerto Rico, Mayaguez; Fernando Cervig6n, Museo Historia Natural La Salle de
la Estaci6n de Investigaci6nes Marinas de Margarita, Venezuela; John E. Randall,
The Bernice P. Bishop Museum, Honolulu; Ralph W. Yerger, Florida State Univer-
sity, Tallahassee; and Giles W. Mead, then of the Museum of Comparative Zoology,
Harvard University.

Special thanks go to my wife, Veronica, for her efforts in typing and proofread-
ing several drafts of the manuscript.

Portions of this study were supported by a grant from the Old Dominion Univer-
sity Research Foundation to the author and from National Science Foundation grants
GB4389, GB5614, and GB7015 to C. Richard Robins.

METHODS

Much of the material used in this study was cleared by the trypsin technique of
Taylor ( 1967), and the bones were stained with Alizarin Red-S. Specimens were
stored in 100% glycerin. Many specimens were dissected after clearing and stain-
ing for more specific examination. Skulls were disarticulated by heating them in a
diluted KOH solution. Many additional specimens were radiographed and data on
several characters, principally of the axial skeleton, were obtained from these flms.
Observations and illustrations were made using a Wild M-5 dissecting microscope
with camera lucida attachment. The nomenclature of the bones follows that of
Springer ( 1968).

I have devised the following notational procedure to facilitate the discussion of
the arrangement and relationships of the spinous dorsal fin pterygiophores with the
underlying vertebrae. The notation consists of an initial digit that indicates the
interneural space ( space between neural spines of the vertebrae) into which the
first pterygiophore is inserted (j.e., the starting point of the spinous dorsal Bn in re-
lation to the vertebral column). Following the initial digit is a series of numbers
in parentheses. Each digit within the parentheses represents an intemeural space,
and the digit is the number of pterygiophores that insert into that space. .All the
interneural spaces between the origin of the spinous dorsal fin and the origin of the
soft dorsal fin are accounted for in the formula. For example, the notation for
Microgobius signatus ( Fig. 11 ) is written as 3 ( 221110). Starting with the third
interneural space, the pterygiophores are inserted as follows: 2 pterygiophores in
space 3,2 in space 4, 1 in space 5, 1 in space 6, 1 in space 7, and 0 in space 8.
The insertion of the first pterygiophore of the soft dorsal Rn is implied in the formula;
in this example it inserts into space 9.

The condition in which pterygiophores are present without associated spines is
noted by an italicized number. For example, the formula for some specimens of
Evermannichthys silus would be given at 3( 122111), indicating that the pterygi-
ophore inserting in interneural space 8 bears no spine. This method of indicating
the arrangement of the pterygiophores is not adequatf for the description of all con-
ditions found in gobioid fishes, and it will be expanded upon in another study.

MATERIALS EXAMINED

The following list is of selected material. An additional several thousand speci-
mens from over 300 nominal species of gobioid fishes have been examined from
cleared and stained material or radiographs, and information has been drawn from
these in the preparation of this paper. The standard length is given in parentheses.
All material has been cleared and stained except as indicated.

Letter combinations appearing as prefixes to catalog numbers stand for the fol-
lowing museums and institutions: ANSP ( Academy of Natural Sciences, Philadel-
phia); BPBM ( Bernice P. Bishop Museum, Honolulu); FSU ( Florida State Uni-



138 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

versity, Tallahassee); GCRL (Gulf Coast Research Laboratory, Ocean Springs,
Mississippi); MCZ ( Museum of Comparative Zoology, Harvard University); MHNLS
( Museo Historia Natural La Salle de la Estaci6n de Investigaci6nes Marinas de
Margarita, Venezuela); ODU ( Old Dominion University, Norfolk, Virginia), SIO
( Scripps Institute of Oceanography, La Jolla, California); (SU Stanford University,
collections now deposited at the California Academy of Sciences, San Francisco);
UCLA ( University of California at Los Angeles); UF ( Florida State Museum,
University of Florida, Gainesville); UMML ( University of Miami, Rosenstiel School
of Marine Sciences, Miami); UPR ( University of Puerto Rico, Institute of Marine
Biology, Mayaguez); and USNM ( U.S. National Museum of Natural History, Wash-
ington, D.C.).

Microgobius signatus ANSP 105182, 5 males ( 40.1-52.0), 7 females ( 41.0-47.0),
Caribbean, Venezuela; MCZ 27130, 8, radiograph, Caribbean, Cuba.

Microgobius microlepis UMML 11821, I female ( 28.8), Atlantic, Fla.; UMML 11814,
1 male ( 32.5), Atlantic, Fla.; UMML 24737, 3( 23.3-29.7), radiograph, At-
lantic, Fla.; UMML uncat., 22, radiograph, Atlantic, Fla.

Microgobius guloms UMML 8795, 3 males, 3 females ( 25.4-31.5), 56(20.3-29.7),
radiograph, Gulf of Mexico, Fla.

Microgobius thalassinus UMML 8808, 2 males ( 27.2-28.7 ), 1 female ( 27.0 ), Gulf of
Mexico, Fla.; USNM 116649, 10, radiograph, Atlantic, N. C.

Microgobius carri UMML 7581 , 1 male ( 26. 5 ), Atlantic, Fla.; UMML uncat., 1 male
( 32.0), 1 female ( 28.5), Atlantic, Fla.; FSU 18792, 7( 34.3-54.8), radiograph,
Gulf of Mexico, Fla.

Microgobius meeki UP.R 2361, 1 male (25.9), Caribbean, Puerto Rico; UPR 2398,
2( 14.7, 16.0), Caribbean, Puerto Rico; MHNLS uncat., 1 female ( 31.8), Carib-
bean, Venezuela; USNM 49367, 1 male ( 29.1), holotype, radiograph, Caribbean,
Puerto Rico.

Microgobius emblematicus USNM uncat., 1 male ( 36.2 ), 1 female ( 36.9 ), Pacific,
Panama; UCLA W54-41, 3, radiograph, Gulfo de Nicoya, Mex.; UMML 24746,
10( 16.3-26.3), radiograph, Pacific, Panama.

Microgobius bret,ispinis SIO 62-106, 1 male ( 52.0 ), 2 females ( 61.5-62.7 ), Pacific,
Baja Calif.; UMML 23810, 1 ( 14.9), Pacific, Panama; SIO 62-719, 35(24.5-
63.7), radiograph, Pacifc, Baja Calif.

Microgobius tabagensis USNM uncat., 1 male ( 33.2 ), 1 female ( 37.0 ), Pacific,
Panama; UCLA W52-254, 1 male ( 39.9), 1 female ( 39.2), Pacific, Baja Calif.;
USNM 81844, 1 female ( 36.2), radiograph, holotype, Pacific, Panama; SIO
64-84, 9, radiograph, Pacific, Baja Calif.

Microgobius curtus UMML 23812, 1 female ( 36.1), radiograph, Pacific, Panama;
UMML 23813, 1 female ( 39.4), radiograph, Pacific, Panama; UMML 23811,
1 male ( 39.3), radiograph, Pacific, Panama.

Microgobius efectus SIO 64-740, 1 male (36.9), 1 female (36.7), Pacific, Panama;
SIO 64-354, 7, radiograph, Pacific, Panama.

Microgobuis cyclolepis SIO 64-875, 1 male (  49.7), 1 female ( 49.0), 23 specimens
radiographed, Pacific, Baja Calif.

Microgobius mira#orensis UCLA W52-44, 1 male ( 36.9), 1 female ( 31.9), 17 speci-
mens radiographed, Gulf of Calif., Mex.

Microgobius crocatus GCRL uncat., No. 1356, 1 male ( 29.3 ), 1 female ( 37.2 ),
Pacific, El Salvador; USNM 202587, 1 male ( 30.6), radiograph, holotype,
Pacific, Panama.

Amma histrio USNM 167583, 2(  37.5, 39.6), radiograph, Gulf of Calif.
Barbutifer antennatus USNM 202375, 2, radiograph, Caribbean, Barbados.
Barbulifer pantherinus USNM 167580, 2 ( 28.9, 33.8), radiograph, Pacific, Mex.
Bollmannia boqueronensis UMML uncat., P-751, 1 male (45.0), 1 female (35.2),

Atlantic, Venezuela; USNM 49366, 1 ( 70.0), radiograp.h, holotype, Caribbean,
Puerto Rico.



1975 BIRDSONC : MICROGOBIUS SIGNATUS OSTEOLOGY 139

Botlmannia chlamydes USNM 93825, 1 male ( 75.0), radiograph, lectotype, Pacific,
Colombia; USNM 41158, 1 female ( 80.5), radiograph, paralectotype, Pacific,
Colombia.

BoUmannia communis USNM 119873, 1 ( 83.2), radiograph, holotype, Gulf of Mexico,
La.; USNM 119889, 2, radiograph, paratypes, Gulf of Mexico, Tex.

Bottmannia litura UMML 21840, 1 male ( 47.5), Atlantic, Venezuela; UMML uncat.,
P-723, 1 male ( 46.2 ),1 female ( 49.3 ), Atlantic, Venezuela; USNM 93797, 1
male ( 39.0), radiograph, holotype, Caribbean, Dominican Republic.

Bollmannia umbrosa USNM 107289, 4, radiograph, paratypes, Pacific, Panama.
Chriolepis benthonis USNM 47671, 1 ( 31.4), radiograph, holotype, Caribbean, Mex.
Chriolepis jishefi SU 37262, 1 ( 18.8), radiograph, holotype, Caribbean, Barbados.
Chriolepis tagus USNM 123232, 1 ( 16.4), radiograph, holotype, Pacific, Galapagos.
Eleotrica cableae USNM uncat., S. E. P. B. O. P.-HA110, 4(35.6-46,2), radiograph,

Pacifc, Galapagos.
Enypnias aceras USNM 81835, 1 ( 37. 5 ), radiograph, paratype, Pacific, Panama .
Enypnias seminudus UMML 23457 2( 24.3, 26.0), Pacific, Panama.
Evermannichthys convictor ANSP 111863, 2(14.8, 15.7), radiograph, paratypes,

Atlantic, Bahamas.
Evermannichthys metzelaari ANSP 111869, 1( 25,2), radiograDh, Atlantic, Bahamas.
Ecermannichthys silas ANSP 111868, 1 male ( 15.5), paratype, Atlantic, Bahamas;

ANSP 111866, 7( 14.5-18.9), radiograph, paratypes, Atlantic, Bahamas.
Evermannichthys spongicola ANSP i10897, 1 ( 20.0), Atlantic, N. C.
Gobiosoma bosci ODU 68-2, 2 males ( 28.5, 34.1), 2 females  (29.0,29.5), Chesa-

peake Bay, Va.
Gobiosoma macrodon UMML 1612, 2(25.1, 26.2), Atlantic, Fla.
Gobiosoma nudum UMML 23454 2 ( 20 .0 , 22 . 5 ), Pacific, Panama .
Gobiosoma polyporosum UMML 24452, 1 ( 27.9), radiograph, paratype, Pacific,

Panama.
Cobiosoma puncticulatum UMML 23472, 1 male ( 27.3), Pacific, Panama.
Gobiosoma robustum UMML 314, 1 male ( 24.7), 1 female ( 24.0), Atlantic, Fla.
Cobutus crescentalis MCZ uncat., IR-116, 1 ( 21.8), radiograph, Pacific, Panama.
Cobulus hancocki USNM 107192, 1 ( 29.0), radiograph, holotype, Pacific, Panama.
Gobulus mversi USNM 107283, 1 ( 27.0), radiograph, hblotype, Gulf of Mexico, Cape

Sable.
Gymneleotris seminudus UMML 13663, 2(31.0, 31.6), radiograph, Pacific, Panama.
Palatogobius paradoxus UMML 23118, 1 male ( 26.3), Caribbean, Panama.
Pariah scotius ANSP 111861, 2( 21.5, 24.4), paratypes, Atlantic, Bahamas; ANSP

111855, 1( 16.3), radiograph, holotype, Atlantic, Bahamas; ANSP 111856,
1 ( 10.5), radiograph, paratype, Atlantic, Bahamas; ANSP 111857, 1(18.5), radio-
graph, paratype, Atlantic, Bahamas; ANSP 111859, 2( 17.4, 19.4), radiograph,
paratype, Atlantic, Bahamas.

Pafretta fusca USNM 107295, 1 ( 30.4), radiograph, holotype, Pacific, Panama,
Parrella macropteryx UMML uncat., P-723, 1( 38.9), Caribbean, Venezuela; UMML

22879, 1, radiograph, Caribbean, Colombia.
Parrella maxillaris UMML uncat., Argosy-55, 1 female ( 23.8), Pacific, Ecuador;

USNM 119901, 1, paratype, radiograph, Gulf of Calif.
Parrella spilopteryx USNM 107293, 1 male ( 52.0 ), radiograph, holotype, Pacific,

Panama.
Psilotris batrachodes UMML 9460, 1( 10.3), radiograph, paratype, Caribbean, British

Honduras.
Psilotris celsus UMML 12926, 1 ( 14 .3 ), radiograph , Atlantic .
Pycnomma. roosevelti USNM 108139, 1 ( 15.6), radiograph, holotype, ·Caribbean, Old

Providence Is.; USNM 107108, 1 ( 13.9), radiograph, paratype, same locality.
Pycnomma semisquamatum SIO 65-273, 4( 31.5-34.3 ), radiograph, Gulf of Calif, Mex.
Tukugobius carpenteri USNM 143819, 2 males ( 40.0-49.0), 2 females ( 36.9-37.6),

Indo-Pacific, Philippine Is.



140 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

Various bucca USNM 143022, 1 ( 19.2), radiograph, paratype, Caribbean, Cuba.
ADDITIONAL COMPARATIVE MATERIAL: Asterropterix semipunctatus USNM 161220,

Philippine Is.; Bostrichthys sinensis USNM 57693, Japan; Butis gymnopomus
USNM 161177, Borneo; Chasmichthys dolichognathus USNM 70754, Japan,
Chloea morarana USNM 71445, Japan; Cor!/Phopterus .glaucofraenum ODU
uncat., Fla.; Dormitator maculatus UMML 5641, Fla.; Erotelis armiger UMML
uncat., Panama; Eviota abax USNM 71405, Japan; Clossogobius giurus USNM
99733, Philippine Is.; Gnatholepis thompsoni UMML 12668, Fla.; Gobiodon
citrinus USNM 166998, Egypt; Gobiomorphus huttoni ODU uncat., New Zea-
land; Gymnogobius macrognathus USNM 105175, Vladivostok, USSR; HI/psele-
otris modestus USNM 161198, Philippine Is.; Ioglosms camurus UMML 18893,
Fla., Lophogobius cyprinoides ODU uncat., Fla.; Microdes,nus #oridanus UMML
20257, Fla.; Petiophthalmus cantonensis USNM 161015, Philippine Is.. Pterele-
otris heteropterus BPBM uncat., Hawaii; Sicydim plumieri UMML 1887; Try-
pauchen vagina ODU uncat,, India; Typhlogobius califomiensis MCZ 33181,
Calif.; Zonogobius semidoliatus USNM 160966, Philippine Is.

OSTEOLOGY OF Microgobius signatus PoEY

HEAD REGION
VOMER ( FIGS. lA, 2,3).-The toothless vomer (V) is a dorsoventrally

f[attened bone, anteriorly broadened and posteriorly produced into a
narrow process. The posterior process is overlapped by, and closely
joined to, the anterior extention of the parasphenoid ( PS). The broad,
anterior portion of the vomer is completely overlain by the ethmoid car-
tilage.

MEDIAN ETHMOID ( FIGS. 1,2,3,8).-The large complex median
ethmoid bone (ME) is dorsally overlapped by the frontals (F) and
ventrally joined through cartilage to the parasphenoid ( PS). The antero-
lateral surfaces are synchondrally joined to the respective lateral ethmoids
( LE). The anterior face is produced into two transverse shelves to
form a deep groove into which the posteromedial portion of the ethmoid
cartilage is inserted. On its dorsal surface two small projections serve
as points of attachment for the maxillary-ethmoid ligaments ( Fig. 8).
A thin, bilaminar sheet of bone projects ventrally from the midline of
the median ethmoid and forms a partial septum between the orbits an-
teriorly. The superior and inferior oblique eye muscles originate on the
median ethmoid just anterior to the median septum.

LATERAL ETHMOID ( FIGS. 18,2,3,8).-The paired lateral ethmoids
(LE), ( prefrontals of Starks 1901 ) are laterally projecting fan-shaped
bones that form the major portion of the anterior walls of the orbits. The
lateral ethmoid forms a syndesmotic joint with the anterolateral surface
of the median ethmoid ( ME). Anteromedially, there is a small shelf
that articulates with the ethmoid process of the palatine ( PAL). At its
lateroventral corner the lateral ethmoid articulates with the lacrymal
(LAC).



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 141

HYO

AN-7 
, PTM

PAL
SCL

LAC
OP

PMX SOPMX MPT 7*, POP
PT SYM BR

EH
D IOPART CHQU

UH

SOC8
ME EPO

E0LE

0. 0V = BO
INT

STF
SPH PRO PTO

FIGURE 1.-Skull of Microgobius signatus. A ) articulated skull (lateral view), B)
cranium (lateral view).

FRoNTAL (FIGS. 18, 244).-The frontal bones (F), paired in more
generalized gobioids, form a synostosis where they meet along the mid-
line. The fused frontals are narrow between the orbits, but broaden
posteriorly to form most of the anterior half of the cranial roof. Each
lateral margin bears a deep trough that carries the supraorbital latero-
sensory canal. Between the orbits the supraorbital troughs lie parallel
and share a common wall along the midline. Posteriorly, the troughs



142 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

A V
ME

ps

F
PTS

f PRO
soc

STF

EPO
INT

IO
BO

FIGURE 2.-Cranium of Microgobius signatus. A) dorsal view, B) ventral view.

diverge in an inverted "Y' shape. Starting at the divergence of the
troughs and running posteriad, the frontals form a sagittal crest that is
confluent with the sagittal crest of the supraoccipital bone ( SOC). The
frontal overlaps the median ethmoid ( ME) anteriorly and the sphenotic
( SPH), pterotic ( PTO), epiotic ( EPO), and supraoccipital posteriorly.
On its ventral surface, near the posterior portion of the orbit, the frontal
forms a synarthrosis with the pterosphenoid ( PTS).

SPHENOTIC ( FIGS. lA-B, 2,4).-The paired sphenotic bones ( SPH)
form the posterolateral margins of the orbits. The sphenotic is over-
lapped by the frontal bone (F) dorsally and synchondrally joined to the
pterosphenoid ( PTS) anteromedially, the prootic ( PRO) ventromedially,
and the pterotic ( PTO) posteriorly. The ventral surface of the sphenotic
bears a shallow articular fossa for articulation with the anterior condylar
surface of the hyomandibular ( HYO ). A small foramen pierces the
laterally extending wing of the sphenotic. Two shelves of bone along
the lateral surface, above and posterior to the wing, form a short trough
that houses the anterior portion of the postorbital laterosensory canal
(lateral canal of B6hlke and Robins 1968). The trough is continuous
with the supraorbital trough of the frontal bone anteriorly and the post-
orbital trough of the pterotic posteriorly.

PTEROTIC (FIGS. lA-B, 2, 4).-Each pterotic bone ( PTO) forms the
posterolateral wall of the cranium. The pterotic is synchondrally joined
to the sphenotic ( SPH) and prootic ( PRO) anteriorly, the epiotic ( EPO)



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 143

dorsomedially, and the exoccipital ( EO) posteriorly. It is slightly over-
lapped by tbe frontal (F) at its dorsomedial edge and adjoins the sub-
temporal fossa (STF) along its ventromedial margin.

Two shelves of bone extend laterally from the pterotic forming a
trough continuous with that of the sphenotic and housing the posterior
portion of the postorbital laterosensory canal. The two shelves run
roughly parallel from the anterior margin to about midway along the
bone, where they merge to form a single shelf that continues to the
posterior margin of the pterotic. The anteroventral surface of the lower
shelf possesses a shallow fossa for the articulation of the posterior condy-
lar surface of the hyomandibular ( HYO). The main body of the pterotic
( excluding the lateral shelves) is bilaminar with cartilage between the
laminae. On its internal surface, parallel to the external shelves, the
pterotic takes the form of a bony passage which houses the horizontal
semicircular canal. Supratemporal bones are absent.

EPIOTIC ( FIGs. 18, EA, 5 ).-The bilaminar epiotic ( EPO) bones form
a major portion of the posterior cranial roof, occupying not only the
epiotic area, but that area usually occupied by the parietals. The parie-
tai bones are apparently absent in all gobioid Bshes ( Regan 1911, Greg-
ory 1933, Gosline 1955, McAllister 1968).

The epiotic forms a synchondral joint with the pterotic ( PTO)
laterally, the exoccipital ( EO) posteriorly and with its fellow along the
cranial midline beneath the supraoccipital ( SOC). At the junction of
the pterotic, basioccipital ( BO), and epiotic, the epiotic bears a small
posterolaterally directed process that articulates with the dorsal arm of
the posttemporal ( PTM). The epiotic is overlapped anteromedially by
the frontal (F) and supraoccipital bones.

On the internal surface the epiotic is formed into a short canal that
houses the posterior vertical semicircular canal. The location of the
canal is evident on the external surface as a broad, posterolateral[y
oriented ridge.

SUPRAOCCIPrrAL C FIGS. 18, 2A, 3).-The supraoccipital bone ( SOC)
occupies the posteromedial area of the cranial roof. Along its anterior
margin the supraoccipital is rather broadly overlapped by the ~ frontals
(F). Along its posterolateral margins it overlaps the epiotics ( EPO)
and exoccipitals ( EO). Along its midline the supraoccipital sends up a
sagittal crest that is continuous with the sagittal crest of the frontal
bones.

ExocaprrAL (FIGS. 18, 2, 5 ).-The bilaminar exoccipital bones ( EO)
form most of the posterior cranial wall and the walls, roof, and floor of
the foramen magnum. The exoccipitals are synchondrally joined along



144 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

A

1 lit ~Ic« -: 1
_lat -/ · · N

»5¥ /7 °

MEDIAN ETHMOID (L)MEDIAN ETHMOID (V)

A

5-.f .A

L
A

LEFT LATERAL ETHMOID (A) ~

VOMER (V)

\ /4 / A PARASPHENOID ( IN)

I

LEFT PTEROSPHENOID (L)

BASIOCCIPITAL (EX)

1 1
5 MM

FIGURE 3.-Disarticulated cranial bones of Microgobius signatus.

the dorsal midline of the cranium, the joint being overlapped for most of
its extent by the supraoccipital ( SOC). Ventromedial projections of
each exoccipital meet along the midline of the floor of the foramen
magnum, thus overlapping the basioccipital and excluding it from par-



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 145

D

A--~
•L

LEFT SPHENOTIC (EX)
1

CA FRONTAL (EX)

RIGHT PROOTIC (EX) D

-A-~

CsruaL -

F ~4&44<t,Vi26
1 1

LEFT PTEROTIC (EX)

RIGHT PROOTIC (IN) SUPRAOCCIPITAL (EX)
! 1

5 MM
FIGURE 4.-Disarticulated cranial bones of Microgobius signatus.

ticipation in the foramen magnum. Along its dorsoanterior margin the
exoccipital forms a synchondral joint with the epiotic ( EPO ); a similar
joint is formed with the pterotic ( PTO) along the exoccipital lateral
margin. The exoccipital appears to form a suture with the basioccipital



146 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

along the exoccipital's ventromedial margin. The ventroanterior margin
of the exoccipital forms the posterior boundary of the subtemporal fossa
(STF). At the anterior extent of the exoccipital-basioccipital joint the
exoccipital is narrowly overlapped by the intercalar ( INT).

Posteriorly the exoccipital forms a posteroventrally directed condyle,
that articulates with the first vertebral centrum. A lateral bridge of bone
runs from the body of the exoccipital to the condyle, thus obscuring the
vagal foramen from lateral view. Dorsal to the condyle, a small foramen
forms a passageway to the recess housing the vagal foramen. The large
glossopharyngeal foramen pierces the ventrolateral wall of the exoccipital
anterior to the-vagal foramen.

Internally, as viewed through the foramen magnum, the exoccipital
bears a thin ventromedially directed strut of bone with an expanded foot
that is joined to a dorsally projecting fold of the internal lamina of the
basioccipital ( BO). The recess formed between the lateral wall of the
exoccipital and the strut houses the asteriscus. The asteriscus thus rests
on the basioccipital, is medially confined by the exoccipital strut and the
fold of the basioccipital, and is laterally confined by the wall of the ex-
occipital.

BASIOCCIPrrAL ( FIGS. 18, 2, 3).-The basioccipital bone ( BO) forms
the posteromedial cranial floor. The bone is bilaminar ( at least an-
teriorly) and approximately Y-shaped in ventrodorsal aspect. The arms
of the Y project anteriorly, while the stem projects posteriorly as the
large circular centrum-like surface articulating with the centrum of the
first vertebra. The basioccipital-exoccipital joint was described above.

Along the anterior margin of each arm of the Y the basioccipital
forms a synchondral joint with the respective prootic ( PRO). Internally,
the basioccipital arms form dorsally-projecting and divergent folds of the
inner lamina that are continuous with similar folds on the respective
prootic bones. Additionally, the anterior portion of the basioccipital is
overlapped laterally by the intercalars ( INT) and medially by the para-
sphenoid ( PS), thus obscuring the notch between the basioccipital arms
and most of the basioccipital-prootic joints from external view.

On each posterolateral surface of the articular extension the basioc-
cipital receives a Baudelot's ligament.

INTERCALAR ( FIGS. 18, 2B, 5).-The paired intercalars ( INT) are
small thin bones applied to the ventral surface of the cranium and
separated by ( but not touching) the posterior portion of the parasphe-
noid ( PS). Anteriorly the intercalar slightly overlaps the prootic ( PRO),
and posteriorly it overlaps the.exoccipital (EO) and basioccipital ( BO).
The lateral margin of the intercalar forms the medial boundary of the



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 147

~ff~~~h D

1-3\-//
LEFT EXOCCIPITAL (IN)

LEFT EXOCCIPITAL (EX)

A
A

RIGHT INTERCALAR (EX)

' LEFT EPIOTIC (EX)
IMM

8 D
D  1 /-\

A ./9

(Ml (P)

LAPILLUS

D

i .7
(M) (P)

(M) (P)
ASTERISCUS

SAGITTA
1 1

IMM
FIGURE 5.-A ) Disarticulated cranial bones of Microgobfus signatus, B) Otoliths of

Microgobius breuispinis.



148 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

8

A

PTO
Ps,-  2F SPH

j ' ;' PRO
0

V VU

3 INT

FIC PS 80

FIGURE 6.-Microgobius signatus. A ) Left prootic and surrounding bones in ventro-
lateral view, B ) Internal view of parasphenoid and surrounding bones showing
the origins of the rectus muscles of the eyes: (1) medial rectus; (2) inferior
rectus; (3) superior rectus; (4) lateral rectus.

subtemporal fossa ( STF). The intercalar bears no foramen as reported ~
in Eleotris fuscus by Freihofer ( 1970: 253).

Near its posterior margin the intercalar bears a posterolaterally di-
rected process to which the ventral arm of the posttemporal ( PTM) ( See
Fig. 10A) is ligamentously attached.

SUBTEMPORAL FOSSA ( FIGS. 18, 2B).-The paired subtemporal fossae
( STF) are large cartilagenous areas of the posterolateral floor of the
cranium. Each fossa is bound by the prootic ( PRO) anteriorly, exoc-
cipital ( EO) posteriorly, intercalar ( INT) medially, and the pterotic
( PTO) laterally. The large sagitta rests on, and is plainly visible
through, the subtemporal fossa.

PRooT[c (FIGS. 18,2B, 4,6).-The paired prootic bones ( PRO) form
the anterolateral floor of the brain case. Laterally the prootic forms
synchondral joints with the sphenotic ( SPH) and the pterotic ( PTO);
posteriorly it forms the anterior margin of the subtemporal fossa ( STF)
and is overlapped by the intercalar ( INT) posteromedially and the par-
asphenoid ( PS) medially.

The anterior margin of the prootic is deeply notched in anteroventral
view. This notch forms the ventral and lateral walls of the large anterior
trigemino-facial foramen. The dorsal margin of this foramen is formed
by the pterosphenoid ( PTS), which bridges the notch. The pterosphe-
noid overlaps the prootic on the medial side of the notch and forms a



1975 BIRDSONG : MICROGOBIUS SIGNATUS OSTEOLOGY 149

synchondral joint with the prootic on the lateral side of the notch. The
prootic is also pierced by the large facial foramen, which is just posterior
to the trigemino-facial foramen. Both of the5e foramina open directly
into the brain cavity, and there is no formation of a pars jugularis.

The internal lamina of the prootic is formed into a dorsally-projecting
fold that is continuous with a similar fold on the basioccipital. The fold
serves to laterally bound the utriculus, which lies in a recess on the floor
of the prootic.

PTEROSPHENOID (FIGS. PB, 3, 6).-The paired pterosphenoid bones
(PTS) ( dermosphenotic of Miller 1963: 226, alisphenoid of Matsubara
and Iwai 1959: 31, and Miller 1973: 399) lie beneath the frontal bones
( F) near the posterior ends of the orbits. The pterosphenoid is com-
posed of a bilaminar, roughly semicircular «body" with a ventromedially
projected process. The body of the pterosphenoid is synchondrally
joined to the frontal, sphenotic ( SPH) and prootic ( PRO) bones. The
ventromedial process is synchondrally joined to the parasphenOid (PS)
and overlaps a portion of the prootic. The participation of the ptero-
sphenoid in the formation of the trigemino-facial foramen and its rela-
tionship to the prootic have been described above.

PARASPHENOID ( FIGS. 18, 2B, 3, 6 ).-The parasphenoid ( PS) forms
much of the medial floor of the skull. Anteriorly the parasphenoid is pro-
duced into a narrow process that separates the orbits and, at its anterior
extent, overlaps the posterior process of the vomer (V), The parasphe-
noid overlaps the prootics ( PRO) laterally and the basioccipitals ( BO)
posteriorly. Near the posterior margins of the orbits the parasphenoid
is broadened to form laterally projecting wings. Each wing forms a
synchondral joint with the ventromedial process of the respective ptero-
sphenoid ( PTS).

Just posterior to the wings, near,the lateral margins, the parasphenoid
is pierced by two foramina for the passage of the internal carotid arteries.
The formation of these foramina is variable, sometimes being formed as
openings in the parasphenoid ( as illustrated in Figs. 2B and 3) and some-
times as deep notches in the parasphenoid that are laterally bound by the
underlying prootics ( Fig. 6).

On the internal surface of the parasphenoid, at the level where the
bone abruptly broadens, a thin, dorso-anteriorly directed shelf of bone
is formed across the midline ( Figs. 3 and 6B). The shelf is the point
of origin of the medial, superior, and inferior rectus muscles of the eyes.
These muscles are dorsally excluded from the brain cavity by a thick
membranous sheet. The lateral rectus muscles, unlike the others, enter



150 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

the brain cavity and run posteriad along the floor to their point of origin
on the basioccipital.

The basisphenoid is absent.

LACRYMAL C FIG. IA).-The paired lacrymal bones ( LAC) are the
only remaining vestiges of the infraorbital series. Each thin, triangular
lacrymal is loosely joined by a ligament to the ventrolateral corner of its
respective lateral ethmoid (LE). A small foramen pierces the lacrymal
near the anterodorsal corner.

NASAL (FIG. lA).-The paired nasal bones (N) lie suspended in
connective tissue over the ethmoid region of the skull. Each nasal forms
a poorly-ossified roofiess trough that is contiguous with the supraorbital
trough of its respective frontal bone and houses the anterior extent of the
supraorbital laterosensory canal.

OToLITHs ( FIG. 5).-The condition of the material does not permit
a detailed description of the otoliths. Those 8gured are from a closely
related species, Microgobius bret)ispinis, and resemble the otoliths of
M. signatus at least in gross configuration and relative size.

UPPER JAw ( FIGs. lA, 7c-E, 8).-Each premaxilla ( PMX ) bears three
processes: (1) an ascending process ( ASC PMX ), which parallels its
fellow along the premaxillary symphysis; (2) a large articular process
(AR PMX), which receives the medial head of the maxilla ( MX); and
( 3) a postmaxillary process ( PM PMX ), which slides under the shaft of
the maxilla when the jaws are closed. The premaxillary teeth are situ-
ated in two poorly-defined. rows; an outer row of 6-8 large recurved cani-
noid teeth and an inner row of 20-30 smaller caninoid teeth.

Each maxilla ( MX ) is composed of a long thin shaft with two pro-
cesses at its proximal end: a medial process ( M MX) that articulates
with the posteroventral surface of the articular process of the premaxilla,
and a shorter lateral process ( L MX) that bears a recessed lateral sur-
face for articulation with the maxillary process of the palatine ( MX
PAL). Of some interest is a dorsal slip of the large adductor mandi-
bulae, which inserts midway along the maxillary shaft. Anteriorly this
slip is quite discrete, but posteriorly the fibers appear to merge with
those of the main body of the adductor mandibulae. This slip of muscle
appears similar to the levator maxillae superioris said by Rosen and Pat-
terson ( 1969) to be characteristic of paracanthopterygian fishes.

The major ligamentous attachments of the upper jaw are described in
the legend to Figure 8. In addition, other ligaments connect the posterior
tip of the maxilla to (1) the anterolateral face of the dentary, (2) the
coronoid process of the dentary, and (3) the posterior tip of the pre-
maxilla.



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 151

OP
A ETH PAL

HYO
PAL \7

MX PAL
MPT

SYM SOPPT

QU /H

lor POP

B
C

V"

HYO

D
(Er- 81 UX

POP

L. L /X

EA~--ASC PUX

1~ br AR PIX COR D -

2 46 1 -/~~r p. m F AWQ ,,All d L A 11 7 1 ,-SES1.lit / :1/

~.1 REPLACEMENT TOOTH - 'V

' ART-1 ANG--1IMM

FIGURE 7.-Suspensorium, opercular bones and jaws of Microgobius signatus. A)
articulated suspensorium and opercular bones (left lateral view), B) medial
view of left hyomandibular, interhyal and preopercle, C) left maxilla (lateral
view ), D) Ieft maxilla ( dorsal view ), E) left premaxilla, F) left articulated
lower jaw bones.



152 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

PMX- V 1

-- 2
MX )tz-3

4PAL : - 3<L~kj

RC  1£f.: 4. \,34 56
7

ME
F -

FIGURE 8.-Ligamentous attachments of the upper jaw of Microgobius signatus
( dorsal view). Stippled lines represent portions of ligaments hidden by bone
in the dorsal view. Key to ligamentous attachments: (1) base of ascending
process of the premaxilla to medial head of maxilla; (2) articular process of
premaxilla to medial head of maxilla; (3) lateral head of maxilla to maxillary
process of palatine; (4) articular head of maxilla to dorsal projection of median
ethmoid; (5) median head of palatine to postero-lateral ·corner of vomer; (6)
trunk of palatine just below ethmoid process to midline where it joins to its
counterpart and to ascending process of premaxilla; (7) ethmoid process of
palatine to anterior face of median ethmoid.

LowER JAW ( FIGS lA, 7F).-The large dentary (D) dominates the
four bones that form each half of the lower jaw. Anteriorly, it meets
its fellow at the mandibular symphysis, and posteromedially it is formed
into a deep, tapering pocket that receives the dorsal ramus of the arti-
cular ( ART). Posteriad, the dentary is dorsally produced into a large
coronoid process ( COR D), which serves as the primary point of inser-
tion for the massive adductor mandibulae muscles common to gobioid
fishes. A large shelf of bone extends ventromedially along the postero-
ventral surface of the dentary. The teeth are in two poorly-defined rows;
the outer row usually consisting of four enlarged caninoid teeth, and the
inner row of 10-15 smaller caninoid teeth in males and 15-25 teeth in
females.

Posterodorsally the articular bone· (ART) bears a saddle-shaped arti-
cular surface that receives the articular process of the quadrate ( QU).
Anteriorly the articular is formed into two rami, the dorsal ramus joining
it to the dentary and the ventral ramus extending anteriad ventral to the
dentary. Two small foramina pierce the articular bone just ventral to its
articular surface. The slim, cylindrical Meckers cartilage runs longitu-
dinally along the concave medial face of the dorsal ramus of the articular.



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 153

Roughly midway along the medial face of the dorsal ramus a small sesa-
moid articular bone (SES) overlaps the Meckel's cartilage.

The small angular bone ( ANG ) is closely applied to the medial face
of the articular at the articular's posteroventral comer.

HYOMANDIBULAR AND PALATINE ARCH ( FIGS. lA, 7A-B ).-The laterally
flattened hyomandibular ( HYO) bears three cylindrical struts radiating
from near the center of the bone, each capped with a cartilagenous
articular surface. The articular terminations of the anterior and posterior
dorsally directed struts articulate with the sphenotic ( SPH) and pterotic
( PTO) respectively. The articular termination of a posteriorly directed
strut articulates with the opercle ( OP). On its anterior surface the
hyomandibular receives the metapterygoid (MPT). The lateral face of
the hyomandibular bears a posterolaterally directed flange, thus forming
a shallow recess that receives the dorso-anterior face of the preopercle
( POP). The medial face of the hyomandibular bears a large foramen,
which is the entrance to a short canal that exits on the lateral face just
below the flange. The hyomandibular branch of the facial nerve tra-
verses this canal.

The metapterygoid ( MPT) is laterally expanded along its posterior
face, where is is Brmly joined to the hyomandibular dorsally and broadly
connected to the symplectic ( SYM) ventrally. The anterior face is
formed into a thin, laterally flattened flange, which is sexually dimorphic
in its extent with males showing a greater development than females
( compare Fig. lA, a male, Fig. 7A, a female). At its ventral end the
metapterygoid is extended as an unossified cartilage that is firmly bound
to the quadrate.

The symplectic ( SYM ) is a rod-shaped bone with a posteriorly pro-
jecting, laterally flattened Bange on its dorsal end. The anterior face
bears a shallow concavity where, dorsally, it receives the metapterygoid
and, ventrally, the quadrate ( QU). The ventral extremity of the sym-
plectic is ligamentously bound to the medial surface of the posterior arm
of the quadrate.

The quadrate ( QU) is shaped roughly like a V lying on its side. Its
anterior extremity, at the apex of the V, is formed into a saddle-shaped
process that articulates with the mandible. The dorsal arm of the
quadrate is bound posteriorly to the symplectic ( SYM), anteriorly to the
ectopterygoid ( PT), and dorsally to the cartilagenous extension of the
metapterygoid ( MPT). The long, slender ventral arm of the quadrate
is formed into a deep concavity along its ventral surface. This concavity
receives the slender, anteroventral extention of the preopercle ( POP).

The pterygoid-palatine strut of the suspensorium consists 6f the pala-
tine ( PAL) and a single pterygoid bone. The pterygoid bone, pre-



154 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3
...

sumed to be the ectopterygoid ( PT), cannot be disarticulated even upon
boiling in KOH. Posteriorly, the ectopterygoid is bound to the quadrate
( QU); anteriorly, it overlaps the descending process of the palatine.

The palatine ( PAL) is a roughly T-shaped bone composed of a long
descending process firmly bound by ligament to the ectopterygoid (PT),
and a head formed into a medially projecting ethmoid process ( ETH
PAL) that articulates with the lateral ethmoid ( LE), and an antero-
laterally projecting maxillary process that articulates with the articular
surface of the lateral process of the maxillary (  L MX ).

OPERCULAR SERIES (FIGS. lA, 7A-B).-The opercle ( OP) is approxi-

mately triangular in shape. Anteriorly, it bears a process with a concave
anterior face, which articulates with the hyomandibular ( HYO) On the
medial surface two thickened struts of bone radiate from the base of the
articular process, one running posteriorly, the other posteroventrally
toward the margin. Posteriorly and ventrally, the opercle slightly over-
laps the J-shaped subopercle (SOP). The dorsal margin of the opercle
and the posterior margin of the subopercle are both poorly ossified,
blending into dense membranous connective tissue that gives the bone a
ragged appearance in cleared and stained specimens.

The crescent-shaped preopercle ( POP) bears a deep groove along its
dorsoposterior margin. This groove houses the preopercular portion of
the laterosensory canal system. Dorsoanteriorly, the preopercle is
closely bound by ligament to the hyomandibular ( HYO); and ventrally,
it extends forward as a slender arm, that inserts into the concaved ven-
tral surface of the ventral arm of the quadrate. Ventral to the hyomandi-
bular, the opercle is anteriorly expanded into a thin shelf. This shelf is
well removed from the symplectic ( SYM) and bears no symplectic pro-
cess. Midway along the dorsoventral extent of its medial surface, the
preopercle is ligamentously bound to the interhyal.

The thin, blade-like interopercle ( IOP) lies ventromedial to the pre-
opercle ( POP) and quadrate ( QU) arms. Anteriorly, the interopercle
is ligamentously bound to the angular ( ANC); posteriorly, it sends a
short ligament to the epihyal ( EH) and a longer ligament to the rather
distantly removed subopercle ( SOP).

Hyom ARcH ( FIGs. 7A, 9c-E).-The small cylindrical interhyal ( IH)
serves as the posterior suspensory element of the lower portion of the
hyoid arch. 6n each end it bears a cartilagenous articular cap. Liga-
ments bind it dorsally to the hyomandibular ( HYO) and ventrally to the
epihyal ( EH). On its lateral surface the interhyal bears a small shelf
from which a stout ligament runs to the medial surface of the preopercle
(POP).



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 155

SH

A ~~~ CARTILAGE VH

\\ *offfi*-PB 2
38 1

EB 1- "Aj{ v. M CH0,/ 74§35-Pa3 832EB 2- -2 ..76 '6
ES 3--*'*¥t j GR 118 2

"r#*19:*F-UPT

1103

\\\\ 084D

.

~ CB 1
CB 2

C83 . ,,€5
CB 4 (8 LPT + CB 5

E A A
BR A 1 Fl BH

D
"1#7 21-VH

DH-f.-~_~
VH--/44-26. 4--7----

CH«f It-UH E ~Un F

FIGURE 9.-Branchial and hyal bones of Microgobius signatus. A) upper branchial
bones (left side, dorsal view), B) hyal and lower branchial bones (branchio-
stegal rays not shown), C ) hyal bones (left side, medial view ), D) basihyal
apparatus (lateral view, left ceratohyal removed), E) basihyal apparatus ( dorsal
view).



156 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

The triangular epihyal (EH) bears an articular surface at its postero-
dorsal corner where it articulates with the interhyal ( IH). Anteriorly,
the epihyal is synchondrally joined to the ceratohyal ( CH).

In lateral view the ceratohyal ( CH) is a cleaver-shaped bone, broad
posteriorly where it joins the epihyal ( EH) and abruptly narrowing
roughly midway of its extent to form an anteriorly projecting "handle."
Anteriorly, the cerathohyal articulates with the small dorsal and ventral
hypohyals ( DH and VH). There is no foramen in the ceratohyal.

There are five branchiostegals ( 81-5). The first, a thin rib-like ray,
articulates with the ventral surface of the narrow portion of the cerato-
hyal ( CH). The next three rays are blade like and articulate with the
ventrolateral surface of the broad portion of the ceratohyal. The pos-
teriormost branchiostegal is by far the broadest and articulates with the
ventrolateral surface of the epihyal ( EH).

The roughly bell-shaped dorsal hypohyal (DH) is firmly bound to the
anterodorsal surface of the ceratohyal ( CH). The similarly shaped, but
oppositely directed, ventral hypohyal ( VH) caps the combined dorsal
hypohyal-ceratohyal anterior face and forms a synchondral joint with
both of these bones. Medially, the ventral hypohyal articulates with its
mate.

The basihyal (BH ) is the anteriormost of the two medially situated
unpaired hyal bones. This V-shaped bone is formed of two divergent
cylindrical struts, each anteriorly capped with a dome-shaped cartilagen-
ous extension. A thin shelf of bone is formed across the crotch of the
basihyal and the posterior tip ( base of the V) is laterally expanded.
The urohyal ( UH) is a dorsoventrally broadened, laterally flattened bone
lying in the midline just posteroventral to the basihyal. At the antero-
dorsal corner of the urohyal a cone-shaped knob projects dorsally and
receives a large ligament from the posterior tip of the basihyal. Addi-
tional ligamentous attachments of the anterior portion of the hyoid arch
are shown in Fig. 90-E. This portion of the hyoid apparatus is inter-
connected by large amounts of thin sheet-like connective tissue, much of
it difficult to discern. The ligamentous attachments illustrated represent
only the most well-defined bundles of fibers.

BRANCHIAL ARCHES ( FIGS. 9A-B).-The upper pharyngeal bones are
represented by epibranchials 1-4 (EB), pharyngobranchials 2-3 ( PB)
( fused with their respective pharyngeal tooth plates), and pharyngeal
tooth plate 4 ( UPT). Epibranchial 1 is medially bifid with each arm
bearing a cartilagenous extension. Most of the connective tissue su-
spending the branchial apparatus from the brain case is sheet4ike and
obscure in my preparations; however, one long well-defined ligamentous
bundle can be seen connecting the anterior arm of epibranchial 1 with



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 157

the parasphenoid. In Figure 9 the upper and lower pharyngeal bones
of the left side have been separated at the articulation of each epibranch-
ial with the posterior tip of its respective ceratobranchial ( CB).

The unpaired lower pharyngeal bones consist of basibranchials 2-4
( BB). Basibranchial 1 is absent and basibranchial 4 is represented by
unossified cartilage.

The paired lower pharyngeal bones are represented on each side by
hypobranchials 1-3 ( HB) and ceratobranchials 1-5 ( CB) ( ceratobranch-
ial 5 is fused with the lower pharyngeal tooth plate). The paired lower
pharyngeal tooth plates ( LPT) are contiguous but unfused along their
medial margins.

The first branchial arch bears a row of ossified, blade«like gill rakers
along its lateral face. The number of gill rakers ( GR) varies somewhat,
but typically, there is one on the hypobranchial ( HB), about 15-16 on the
ceratobranchial ( CB), and 4-5 on the epibranchial ( EB). Additionally,
the medial face of ceratobranchial 1 and the medial and lateral faces of
ceratobranchials 2-4 all bear a row of 10-15 patches of very small
branchial teeth ( BT). The patches, each bearing from three to over a
dozen tiny teeth, are suspended in the connective tissue surrounding the
ceratobranchials.

PECTORAL GIRDLE AND PAIRED FINS ( FIG. 1OA ),-Each postemporal
( PTM) is anteriorly forked to form a dorsal and a ventral process. The
processes are ligamentously bound to the epiotic (El?0) and the inter-
calar ( INT), respectively. A blade-like supracleithrum ( SCL) is liga-
mentously joined to the posteromedial surface of the posttemporal and
to the dorsolateral face of the cleithrum ( CL).

The cleithrum ( CL) ( clavicle of Matsubara and Iwai 1959) is an
elongate, crescent-shaped bone, biEd at its dorsal end and articulating
with its mate at the ventral end. Posteriorly, along the central third of
its extent, the cleithrum bears a deep groove into which the scapular
cartilage ( SCA) is inserted. Posteroventrally, the cleithrum is produced
to form a process, which is synchondrally joined to its respective pelvic
bone. The central portion of the lateral surface of the cleithrum bears
a pronounced flange from which the relatively large adductor muscle
mass originates. Baudelot's ligament is attached to the dorsomedial face
of the cleithrum at the crotch of the bifurcation. There are no post-
cleithra.

The completely unossified scapula ( SCA) is represented by an elon-
gate cartilage, which is partially concealed in the posterior groove of the
cleithrum ( CL). Near its dorsal end the scapula is pierced by a large
foramen. Ventrally the scapular cartilage joins the coracoid ( COR).



158 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

A
PTM

SCA

RAD

COR *44

B

D

c L~
11

'IM 
i

FIGURE 10.-Pectoral and pelvic girdles of Microgobius signatus. A) left pectoral
girdle, B) pelvic girdle ( ventral view, fin elements of right side not shown),
C ) right pelvic spine (lateral view).



1975 BIRDSONG : MICROGOBIUS SIGNATUS OSTEOLOGY 159

The coracoid, a roughly bell-shaped bone in lateral view, also forms a
synchondral joint with the posterior surface of the deithrum.

There are four radials ( RAD); the dorsal and ventralmost radials are
triangular and the two nentral radials are roughly rectangular in shape.
The radial margins are surrounded by cartilage, through which they
articulate with each other and with the posterior margin of the girdle.
The pectoral rays, usually 21-22 in number, insert on the posterior
cartilagenous border of the radials. The bases of the pectoral rays,
especially the central rays, are bilaterally asymmetric in structure. The
medial component of each pectoral ray. base bears short dorsal and
long ventral flanges, which overlap with the flanges of the adjacent rays.

PELVIC GIRDLE AND FINS ( FIGS 108, c).-In dorsoventral view each
pelvic bone is formed into a conical anterior projection, which is joined
through cartilage with the pelvic process of the cleithrum ( CL). Pos-
terodorsally, the conical portion of the pelvis bears a thin medially pro-
duced shelf, which forms a symphysis with its mate at the midline.
Posteriorly, the pelvic bone is dorsoventrally thickened and, medially,
bears a ventro-anteriorly projected ventral process. The finger-like
ventral processes of each pelvic bone are contiguous for most of their
extent, but diverge near their tips.

Posteriorly, one spine and five rays are attached to the pelvic bone.
The base of the pelvic spine bears three medially directed processes.
A dorsal and ventral process of the pelvic spine lie over and under,
respectively, the posterolateral corner of the pelvic bone. The medial
process of the pelvic spine bears an articular surface at its tip and
articulates with a posterolateral articular surface on the pelvic bone.
The five rays articulate with the pelvic bone by means of cartilage. As
in most gobiids the centralmost ray is joined to its opposite by a mem-
brane and the opposing pelvic spines are joined by a membranous fren-
um.

VERTEBRAL COLUMN AND MEDIAN FINS

VERTEBRAL COLUMN ( FIGS. 11, 12).-There are 11 precaudal and 16
caudal vertebrae, including the urostylar elements ( US ) ( erroneously
given as 14+ 15 by Jordan and Eigenmann 1886: 514). Caudal vertebrae
( excluding the urostyle) are here differentiated from precaudal verte-
brae by the absence of pleural. ribs ( PR) and the presence of a closed
haemal arch ( HS). This simple distinction is useful for most, but not all
gobioids.

All vertebrae, again excluding the urostyle, bear well developed
neural spines ( NS) and the precaudal vertebrae bear parapophyses



160 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

DORSAL SPINE 7

DORSAL RAY i

PPTG
NS

VT 1252> D FIRST CAUDAL
VERTEBRA

EPR 1
PAP HS

PRI1
PTG

ANAL SPINE

FIGURE 11.-Anterior vertebrae and median fin elements of Microgobius signatus.

( PAP) as well. The parapophyses of vertebrae 9-11 are progressively
larger than those preceding.

The first two precaudal vertebrae bear only epipleural ribs ( EPR),
these articulating with parapophyses or their bases. The succeeding
precaudal vertebrae ( 3-11) bear both pleural and epipleural ribs. The
pleural ribs articulate with the parapophyses and the epipleural ribs
articulate with the pleural ribs. The posterior epipleural ribs become
progressively removed from their respective pleural ribs, with those on
vertebrae 10 and 11 lying in connective tissue some distance posterior
to their associated pleural ribs. Occasionally tiny ossified elements
representing epipleural ribs 13 and 14 are found "floating" in connective
tissue lateral to the two anteriormost caudal vertebrae.

The first vertebra bears lateral processes, which articulate with the
condyles of the exoccipitals. The anterior face of the centrum of the
first vertebra is angled slightly posteroventrally for articulation with the
basioccipital ( BO).

The first vertebra bears well-developed dorsal postzygapophyses.
The second vertebra bears both dorsal pre- and postzygapophyses, while
the third vertebra has only dorsal prezygapophyses ( PZP). The dorsal
zygapophyses on all of the succeeding vertebrae are poorly developed
( absent on the last 34 caudal vertebrae). There are no ventral zyga-
pophyses.

Each of the first 23 vertebrae bears a large foramen through each
lateral wall of the neural arch. A second smaller foramen is occasionally
present in one or both sides of the neural arch of some vertebrae. In



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 161

BRANCHED RAY

-~ HYP 5

VT 25 NS

'. HYP 3-4

. HYP 1-2

- ~5X j· PHYPHS

X:~*~RZO RAY

FIGURE 12.-Caudal skeleton of Microgobius signatus ( median caudal rays not
shown).

vertebrae 24 and 25 there is a single small foramen ( occasionally absent)
on each side of the arch.

The haemal and neural arches of vertebrae 12-22 arise from the
anterior half of the centrum. On vertebra 23 the haemal and neural
arches arise from a more posterior position near the center ( narrow por-
tion) of the centrum. The neural and haemal arches of vertebrae 24-26
arise from the posterior half of the centrum. The neural and haemal
spines of vertebra 25 are laterally Hattened and blade-like.

Vertebra 26 is somewhat modified for participation in the support of
the cau(lai fin. The neural spine ( epural 1 of Johnson 1969: 84) is short
and anteroposteriorly expanded. Each lateral wall of the neural arch
bears a large foramen and one or two smaller foramina are occasionally
present. The haemal spine ( hypural 1 of Johnson 1969: 84) is greatly
elongated and formed into a cylindical strut along its posterior margin.
Each lateral wall of the haemal arch also is pierced by a large foramen,
with one or two smaller foramina of various placement and size being
occasionally present. The caudal artery bifurcates posterior to this



162 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

haemal spine just below the urostyle. Distally, the haemal spine receives
the first segmented ( but unbranched) ray.

CAUDAL FIN ( FIG. 12).-The urostylar element ( US) is composed of
a half centrum, which is totally fused with a large fan-shaped element
representing hypurals ( HYP) 3-4 (hypural 4 of Johnson 1969: 84; hy-
pural 4-5 of Miller 1973: 406). Monod ( 1968) says the urostylar ele-
ments of gobiid caudal fins are composed of the fusion of preural 1 with
the urals. This may be correct, though I have no information bearing
on the matter.

The parhypural (  PHYP) ( hypaxial bone of Miller 1963: 231; hypural
1 of Miller 1973: 406; lower splint-like bone of Gosline 1955: 164;
hypural 2 of Johnson 1969: 84) is a small bone formed of a cylindrical
strut with thin dorsal and ventral flanges. It lies between the last haemal
spine and the lower hypural fan.

Hypurals 1 and 2 ( hypural 3 of Johnson 1969: 84; hypurals 2-3 of
Miller 1973: 406) are fused into a single fan-shaped plate that inserts
anteriorly into a recess on the ventroposterior portion of the urostyle
near the point of fusion of the urostyle with hypurals 3-4.

Hypural 5 (epaxial bone of Miller 1963: 231; hypural 6 of Miller 1973:
406; upper splint-like bone of Gosline 1955: 164; epural 3 of Johnson
1969: 84), similar in size and shape to the parhypural, lies just above the
posterodorsal margin of hypurals 3-4. A single large epural ( epural 2
of Johnson 1969: 84) lies above the urostyle just anterior to hypural 5.
The epural is formed of a cylindrical strut with a large anterior and
small posterior Hange.

There are typically 14 branched and segmented caudal rays, which
insert on the hypural plate as follows: the first ray (lowermost) on the
parhypural, five rays on the cartilagenous posterior margin of hypurals
1-2, seven rays on the cartilagenous posterior margin of hypurals 3-4,
and the last ray on hypural 5. Above and below the 14 branched rays
there are single segmented unbranched rays inserting on the epural and
last haemal spine ( HS), respectively. Preceding the segmented rays,
both above and below, is a series of 7-8 small segmented procurrent
rays, each series inserting along the margin of a large thin sheet of
cartilage. These dorsal and ventral procurrent cartilages ( PC) are con-
tiguous with the dorsal margin of the epural and ventral margin 6f the
last haemal spine, respectively.

SPINOUS DORSAL FIN ( FIG. 11).-The spinous dorsal fins are supported

by seven spines, which articulate with seven pterygiophores ( PTG). The
proximal and medial radials of the spinous dorsal pterygiophores are
totally fused, and the distal radial appears to be absent.



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOCY 163

The number and arrangement of spinous dorsal pterygiophores is
invariable. The first two pterygiophores insert into the third interneural
space ( space between the neural spines); the third and fourth pterygio-
phores insert into the fourth interneural space; and the fifth through
seventh pterygiophores each insert into their respective interneural space.
The sixth and seventh dorsal spines are somewhat more widely spaced
than the preceding five spines. There are no predorsal bones.

SECOND DORSAL FIN.-The second dorsal fin ( D2) is composed of one
spine and 19-21 soft rays, each supported by a pterygiophore ( PTG)
except the last two rays, which share the posteriormost pterygiophore.
The two anterior Dz pterygiophores insert into interneural spaces 9 and
10 respectively and havd their proximal and medial radials fused. The
proximal and medial radials are discrete in all of the remaining D2
pterygiophores. Each of the Da pterygiophores bears a discrete distal
radial except the last, which consists of proximal and medial radials only.
Each distal radial is composed of a pair of bilateral elements, closely
joined to the base of the ray. Soft dorsal pterygiophores 18-20 are in-
serted into interneural spaces 9-22, with interneural spaces 9-13 typically
receiving only a single pterygiophore. The insertion of the remaining
pterygiophores into interneural spaces 14-22 displays some individual
variation, with each· interneural space receiving either one or two
pterygiophores; however, the last pterygiophore nearly always inserts
into interneural space 22 regardless of the number of pterygiophores
present.

ANAL FIN.-The anal fin is composed of one spine and 20-22 soft
rays supported by 19-21 pterygiophores ( PTG). The first anal pterygio-
phore has its proximal and medial radials fused and supports both the
anal spine and the first soft ray. Each of the succeeding pterygiophores
supports a single ray, except the last which supports the two final rays.
The second through penultimate pterygiophores are each composed of a
proximal ( PPTG), medial ( MPTG), and distal radial ( DPTG). The
distal portion is apparently absent in the last pterygiophore. The in-
sertion of the Srst two anal pterygiopliores is invariably anterior to the
first haemal spine. The insertion of the remaining pterygiophores shows
similar variation to those of the soft dorsal Bn, but typically insert into
the first 12 interhaemal spaces with either one or two pterygiophores
per space.

DISCUSSION

The search for the relationships of Microgobius within the genera of
seven-spined gobies has been a quest of limited reward. Before dis-



164 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

TABLE 1.-OSTEOLOGICAL CHARACTERISTICS OF THE GOBIOIDEL

Parietals, basisphenoid, and orbitosphenoid absent.
Epiotic forming a synchondral joint with mate beneath the supraoccipital.
Intercalar reduced (lost in some species).
Infraorbital, except lacrymal, absent in most species ( one reported present in 2 species
of eleotrids by Akihito 1969 and in Rht/adchthys by Miller 1973).
Supratemporals absent in most species ( reported present in 6 species of eleotrids by
Akihito 1971).
Wide separation of the symplectic from the preopercle.
Preopercle attached to quadrate and hyomandibular thus forming a third strut of the
suspensorium.
Symplectic dominates the symplectic-metapterygoid strut of the suspensorium in most
species.
Mesopterygoid reduced or absent.
Interhyal ligamentously attached to preopercle.
Branchiostegal rays 4 to 7 ( usually 5).
First basibranchial absent, fourth basibranchial present as cartilage.
Baudelot's ligament present.
Dorsal postcleithrum absent in all groups except the eleotrids.
Ventral postcleithrum reduced or absent in many species.
Scapula reduced in most species ( cartilagenous in many).
Pectoral radials 3 to 4 ( usually 4).
Vertebral number usually 25 to 27; however, may exceed 60 in some species.
Superneurals absent.
Number and arrangement of spinous dorsal pterygiophores highly stable within most
species, usually 6 to 7.
Penultimate vertebra with a short expanded neural spine and an elongated and ex-
panded haemal spine.
Procurrent caudal rays supported by cartilagendus plates in most species.
Epurals number 1 to 3, usually 1 to 2.
Hypurals 3 and 4 fused to each other and to the urostyle.
Hypurals 1 and 2 fused to each other in all species and to the urostyle in some groups.
Parhypural and hypural 5 greatly reduced.

cussing the osteological evidence bearing on the subject, a more general
discussion of gobioid osteology seems in order. Miller ( 1973) offers a
valuable discussion of the major features of gobioid osteology, including
the available fossil data and a review of gobioid classification. My at-
tempt here is to add to Miller's discussion and, on some points, offer a
different point of view.

Though gobioids are easily defned by osteological characters ( see
Table 1), they are remarkably similar in gross osteology. The distin-
guishing features mostly involve the loss, fusion, or reduction of bone,
Compared to most other teleosts, the gobioids have a highly simplified
skeletal structure. The simplified skeleton, combined with the gross
similarity of the species, makes evolutionary trends difficult to discern
and greatly complicates the task of sorting out convergent characters.
In spite of their great proliferation and the variety of habitats they
exploit, the majority of g6bioids remain rather generalized, benthic
fishes. This is\not to say that osteological evidence will contribute little



1975 BIRDSONG : MICROGOBIUS SIGNATUS OSTEOLOGY 165

to the unraveling of gobioid phylogeny. On the contrary, there appear
to be many useful osteological characters; however, the problems men-
tioned, together with the difficulty encountered in selecting representative
material from the vast array of species, will make progress slow.

Table 1 is an attempt to set forth some of the osteological trends
within. the gobioids. No taxon above the generic level has been ade-
quately studied and these trends are tentative at best. The general-
ized character states given are those found in the monotypic family
Rhyacichthyidae and among the Eleotrididae. These two groups show
less loss and fusion of bone than do other groups of gobioids and on
this basis appear to be the most generalized.

The tentative list of gobioid osteological characteristics appearing here
is drawn from the literature and from my own observations. In the
ensuing discussion I shall briefly elaborate on the occurrence and lability
of some of these characters and attempt to reconcile my observations
with those of other workers.

CRANIuM.-Gosline ( 1955: 163 ) states that the alisphenoid ( =
pterosphenoid) is unknown in gobioid fishes. Pterosphenoid bones have
been reported in Mistichthys ( TeWinkle 1935), Periophthalmus ( Lele
and Kulkarni 1938), Kraemeria C Matsubara and Iwai 1959), Lebetus
( Miller 1963) and in Rhyacichthys ( Miller 1973). Microgobius, Boll-
mannia, Parrella, and Gobiosoma 'all possess well-developed pterosphe-
noid bones, as do all other gobioids that I have examined for this char-
acter.

Regan ( 1911: 729) describes the epiotics as being separated by the
supraoccipital in gobioids. Gosline ( 1955: 163) described a similar
situation in all of the genera he examined except Kelloggella, Kiaemeria,
and Microdesmus. In Microgobius and other American seven-spined
genera, each epiotic forms a synchondral joint with its mate beneath the
supraoccipital. Examination of representatives from Erotelis, Chas-
michthys, Euiota, Ptereleotris, Lophogobius, Gnatholepis, and Coryphop-
terus reveals a condition similar to that found in Microgobius, and in-
dicates the meeting of the epiotics beneath the supraoccipital is at least
common and perhaps typical in gobioids.

The development of a shallow shelf-like myodome on the parasphe-
noid ( as described in M. signatus) for the attachment of the medial,
inferior, and superior rectus muscles appears to be an advanced feature
in gobioids. A similar structure has been observed in such advanced
but diverse genera as Ptereleotris, Periophthalmus, Bollmannia, Parrella,
and others. The parasphenoid shelf is lacking in those eleotrids exam-
ined for the structure ( i.e., Eleotris pisonis, E. amblyopsis, Bostrichthys



166 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

sinensis, and Gobiomorphus huttoni). Dissection of Eleotris amblyopsis
shows the rectus muscles to originate separately along the parasphenoid
in the anteroposterior order of medial, inferior, superior, and lateral
muscles. Unlike the condition in Microgobius, the lateral rectus muscle
penetrates the brain cavity only for a short distance and originates on
the parasphenoid near the carotid foramen.

SUSPENSORIUM.-GOsline (1955: 160) and Miller (1973) have com-
mented upon the unusual nature of the gobioid suspensorium, the most
notable feature being the formation of a posterior strut composed of the
quadrate and preopercle, which is widely removed from the symplectic-
metapterygoid strut. Additionally, there is a tendency in many species
for the symplectic to dominate the symplectic-metapterygoid strut with
the metapterygoid sometimes reduced to a small fragment ( e.g., Mis-
tichthys luzon€nsis [TeWinkel 1935]). Matsubara and Iwai (1959: 30)
failed to find a symplectic bone in Kraemeria sexradiata, though Gdsline
( 1955: 161) has indicated a rather large symplectic in K samoensis. I
suspect that the description of the metapterygoid by Matsubara and Iwai
( 1959: 29, 32) actually is of the combined metapterygoid and symplectic
bones.

Miller ( 1973) placed special importance on the development of an
anteroventral process ("bridge") of the metapterygoid that overlaps
the quadrate and the development of a symplectic process on the pre-
opercle ( see Fig. 14) in defining subfamilies in his classification of
gobioids. My observations show both of these characters to display
considerable lability and suggest the strong possibility of several con-
vergent losses or developments of these features in gobioids. Within
the American seven-spined gobies the occurrence of a quadrate process
is distributed in relation to other characters in such a way as to suggest
that the feature has either been independently lost in several lineages
or devoleped de nouo within the group. Furthermore, some species
(e.g., Periophthalmus cantonensis) display considerable intraspecific
variability in the development of a quadrate process.

The symplectic process shows similar variability, appearing in at
least some species of each of.Miller's subfamilies with the exception of
the Kraemeriinae. In at least one species, Microgobius cyclolepis ( Fig.
13), the symplectic process displays sexually dimorphic development.

The pterygoid-palatine strut of gobioids is characterized by the re-
duction or loss of the mesopterygoid bone ( Gosline 1955: 160). Akihito
( 1969) found a mesopterygoid to be present only in 17 species ( all
eleotrids) among the 106 gobioid species he examined. Even among the
eleotrids the mesopteygoid is lost in some lineages ( e. g., Erotelis and
Gobiomorphus).



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 167

A

5

469
7

2
3

8

B

5 -- 1 \ 4
4  /2£+GA

fu Us64#/

*-0-52 /7 41'
-

0

FIGURE 13.-Selected bones of the jaw and suspensorium of Microgobius cyclolepis
showing sexual dimorphism. A) female, 49.3 mm SL, B) male, 50.4 mm SL.
Key to numbers: (1) maxilla; (2) dentary; (3) articular; (4) ectopterygoid;
(5) metapterygoid; (6) symplectic process of preopercle; (7) symplectic; (8)
quadrate; (9) preopercle.

HYOID A~CH.-Gosline ( 1955: 161) called attention to several char-
acteristic features of the hyoid arch and branchiostegal ray confgura-
tion in gobioids. The main variation from the condition described in
Microgobius is found in Rhyacichthys and in the eleotrids, which possess
an additional branchiostegal on the narrow portion of the-ceratohyal.



168 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

A

D
C

-/.a i

F X=1~~

6,8/29'L,X

E --- Ass~M15*343;1"6'/917&3~99*, 16)/,9):,r~ \4%Ar</ 19 *FJ-KJ ci A . Fl\

~44 1.\ 23</'~

FIGURE 14.-Articulated skull ( branchial bones removed) and cranium ( dorsal view)
of representative Cobiosomini. A, B) Bollmannia boqueronensis, C, D) Parrella
macropteryx, E, F) Gobiosoma bosci.



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 169

The fossil gobioid family Pirskeniidae, from the Upper Oligocene of
Bohemia, is said by Miller ( 1973) to possess six or seven branchiostegals.

An additional unusual feature, the attachment of the interhyal to the
preopercle, has received little attention in the literature. This feature,
described for Microgobius signatus, has been found in all species exam-
ined, including such diverse groups as foglossus, Periophthalmus, Sicyd-
ium, Erotelis, Butis, Coryphopterus, and Gnatholepis, and may be char-
acteristic of gobioids in general.

The absence of the Brst basibranchial also appears to be typical of
gobioids. The anteriormost basibranchial described by Matsubara and
Iwai ( 1959: 30) in Kraemeria sexradiata appears to be the urohyal.
Miller's description of the basibranchials 1-3 in Rhyacichthys appears to
be of basibranchials 2-4.

Takagi ( 1950) attempted to arrange Japanese gobies into a phylo-
genetic sequence based upon the shape of the basihyal. The basihyal
bones of gobioids vary from a long narrow shape ( e.g., Ptereleotris)
to a spatulate shape ( e.g., Bollmannia) or a bifid shape ( e.g., Parrella).
The spatulate and bifid basihyals appear easily derived one from the
other. Virtually nothing is known of the functional aspects of the various
types of basihyals in gobioids and it seems likely that a great deal of
parallelism may have taken place.

PECTORAL GIRDLE.-The most pronounced divergence of the pectoral
girdle from the condition seen in Microgobius signatus is that described
in Kraemeria samoensis (Gosline 1955: 163) and K. sexradiata (Mat-
subara and Iwai 1959: 31). These species lack the ventral arm of the
posttemporal and have only three ossified radials. The reduction or
absence of the ventral arm of the posttemporal has also been reported
for Kelloggella oligolepis ( Gosline 1955: 163) and Microdesmus dipus
(Dawson 1968: 520).

Some confusion exists concerning the absence of scapula and coracoid
bones in many gobioids. Akihito ( 1963, 1967) has shown the degree
of ossification of the scapula in gobioids to be variable. The scapula is
listed as "absent" ( determined by Alizarin Red staining, but perhaps
present as cartilage) in 34 of 106 species examined by Akihito ( 196®.
Likewise, Gosline (1955: 164) states that the scapula is absent in Gobi-
odon and Awaous, and both scapula and coracoid are missing in Micro-
desmus, Ptereleotris, Ketloggella, and Kraemeria; and Miller ( 1973) refers
to the absence of the scapula in several gobioid lines. As in Microgobius
signatus, the scapula is unossified in many gobioids; however, all of the
cleared and stained specimens examined by me, including representatives
of Gobiodon, Microdesmus, and Ptereleotris, have at least a cartilagenous
scapula, and all possess an ossified coracoid. In Periophthalmus the



170 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

scapula appears to be completely fused to the cleithrum ( Lele and
Kulkarni 1939: 130).

Akihito ( 1969) has shown the widespread occurrence of ventral post-
cleithra in gobioids ( 74 of 106 species examined). Among the American
seven-spined gobies, a ventral postcleithrum is khown to occur only in
BoNmannia and Palatogobius. The development of ventral postcleithra
is quite variable in gobioids, sometimes intraspecifically so, and its sys-
tematic importance seems limited.

Dorsal postcleithra appear to be present only among eleotrids and
in Xenisthmus and Gobiomorphus, two genera showing a mix of eleotrid
and gobiid features.

PELVIC GmDLE.-Several groups of gobioids show tendencies toward
the reduction or loss of the pelvic fins (e.g., trypauchenids and micro-
desmids). This tendency is most apparent among elongate, burrowing
forms and reaches its extreme in Expedio parvulus, which appears, from
radiographic observation, to have lost the entire pelvic girdle.

VERTEBRAL COLUMN AND MEDIAN FINs.-Several characters of sys-

tematic importance are present in the vertebral column and median Bns
of gobioids, however, a detailed discussion of these is in preparation,
so my comments here are limited to a few selected features.

The caudal structure of Microgobius appears to be rather character-
istic of gobioids of general. The large amount of consolidation and
simplification characterizing the gobioid caudal skeleton makes interpre-
tation difficult. The fusion of the lower hypural to the urostyle and
hypurals 3-4, as seen in Gobiosoma and derivative genera, is apparently
an uncommon feature ( only reported in Kraemeria and Kelloggella
[Gosline 19551 ), as is the loss of the parhypural and hypural 5 ( reported
in Periophthalmus barbarus [Lele and Kulkarni 1939]).

Gobioids vary from one to three in number of epurals, with only
Rhyacichthys known to have three epurals and the vast majority of
gobioids possessing either one or two. Miller (.1973) utilized the number
of epurals as a fundamental character in separating several of his sub-
families of Gobiidae. The number of epurals appears to exhibit · some
lability, and the character should be used with caution in defining groups
above the generic level. Virtually all of the intermediate conditions be-
tween two discrete epurals and a single fused epural are found in go-
bioids. Eleotrids and some gobiids possess two epurals, each with a
cylindrical strut running through it. Other species have two contiguous
epurals, with only the posteriormost containing a strut. In this latter
condition the two epurals, when considered as a unit, closely resemble
the single epural shown in Fig. 12 for Microgoblus signatus. Some
species of the genus Gobionellus that appear to represent natural as-



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 171

semblages of closely related forms show interspecific variation in epural
number ( Carter R. Gilbert, pers. comm.). Additionally, two species of
gobiids, Tamanka siitensis and Rhinogobius hadropterus, are known to
be variable in epural number and display conditions ranging from two
discrete epurals to partial or total fusion into a single unit. Reduction in
epural number has probably occurred independently several times in
gobioids. Even in some of the more primitive forms, such as Gobio-
morphus huttoni, the epurals are firmly fused into one unit while retain-
ing the two struts typical of eleotrids.

The gobioids show a considerable range of vertebral number ( 25
to 60 + ); however, there is a great intraspeciftc stability in most groups.
Groups showing significant variation in vertebral number are nearly
always burrowing or hole dwelling in habit and frequently elongate in
form. Elongation of the body has been accomplished by the elongation
of the vertebrae in some ( e.g., Taenioides, Gobioides, and Trypauchen)
and by the addition of vertebrae in others ( e. g., microdesmids).

The majority of gobioids possess pleural and epipleural ribs as de-
scribed for Microgobius; however, two different specializations have been
noted. In some elongate burrowing forms (e.g., Inu) the ribs are
greatly reduced in size, and in others ( e. g., Expedio and Leucopsarion )
the ribs are apparently absent. A second specialization, noted only in
Periophthalmus, is a tendency for the epipleural ribs to fuse with the
pleural ribs. These two specializations appear to have rather obvious
functional significance: in the burrowing forms the reduction of ribs
promotes body flexibility, and in Periophthalmus the fusion provides in-
creased support for the viceral cage during terrestrial forays.

Among the numerous minor specializations of the median fins, only
two will receive comment here, and again burrowing species and "ter-
restrial" species are involved. In many burrowing groups ( e.g., Chloea,
Clevelandia, Clariger, Typhlogobius, Inu, and others) the spinous dorsal
fin is greatly reduced in both size and number of elements. Frequently
the pterygiophores are retained without the spines. In at least some
species of the genera Expedio, Luciogobius, Leucopsarion, and Inu no
vestige of the spinous dorsal En remains. The reduction in the spinous
dorsal fin may be attributable to a decrease in the swimming and signal
function in burrowing species.

The specialization of the spinous dorsal fin of the periophthalmids,
a "terrestrial" group, involves the addition of spines to the dorsal fin
without the addition of supporting pterygiophores. The periophthalmids
utilize the erect dorsal fin as a signal during terrestrial activity, and the
accessory spines would appear to give needed support to the fin mem.
brane in an air environment.



172 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

COMPARISON OF M. signatus WITH OTHER SPECIES OF Microgobius.-
The species of Microgobius are remarkably similar in their asteological
features, and few trends within the genus can be discerned.

Microgobius ~ carri diverges most from the condition described for M.
signntus by the absence of a median frontal crest, a narrower, though
still bifid, basihyal, and in having a larger lacrymal bone. Based on
trends seen in gobioids in general, all of these characteristics of M. carri
appear to be primitive. M. carri further differs in having a relatively
large mouth in both sexes and a laterally expanded and trifurcated tip
of the neural spine on the third vertebra. In these two features M. carri
appears to be advanced over other members of the genus; however, the
trends in these characters are obscure. Several species ( M. bret)ispinis,
M. mira#orensis, M. cyclolepis, and the males of M. microlepis) show
some lateral expansion of the second and third neural spines, but none
approach the condition seen in M. carri.

All species of Microgobius, except M. signatus, show small to large
differences in mouth size between the sexes, the mouth of the male being
larger. In M. carri the mouth of the females is also large, though smaller
than the male's, and displays many of the attendant osteological features
only seen in the males of other species. The sexual dimorphism of the
mouth is reflected in several bones of the jaws and suspensorium and
becomes increasingly pronounced in larger, more mature individuals.
In all species of the genus, including M. signatus, the males show a
greater development of the anterior Range of the metapterygoid.

Sexual dimorphism of mouth size is most pronounced in M. gulosus,
M. mirafiorensis, M. crocatus, and M. cyclolepis ( Fig. 13 A,B). The
following list of osteological differences seen in mature males of M.
cyclolepis when compared to females of equal size illustrates the modift-
cations of jaw and suspensorium bones attendant with the increase in
mouth size. These same differences may be seen when small-mouth
species ( e.g., M. signatus) are compared to large-mouth species ( e. g.,
M. carri).

Dentary-longer with greater development of ventral shelf and
coronoid process.

Articular-longer and stouter dorsal and ventral rami.
Premaxilla-longer shaft.
Maxilla-longer and stouter shaft with an expanded and posteriorly

produced distal tip ( distal tip in females is anteriorly recurved).
Ectopterygoid-longer shaft with an expanded base more firmly

sutured to the quadrate.
Quadrate-articular process more ventrally oriented so that dorsal

and ventral arms are oriented anteriorly and posteriorly, re-



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 173

spectively; dorsal arm lengthened; ventral arm dorsally ex-
panded and shortened.

Symplectie-shorter and more vertically oriented.
Metapterygoid-shorter, more vertically oriented and anteriorly ex-

panded as a thin Range.
Preopercle-anteroventral extention shorter, giving preopercle a more

vertical orientation; development of a symplectic process (  this
feature seem only in M. cyclolepis).

In general, the bones of the jaws and the anterior strut of the suspen-
sorium in males are lengthened, whereas the posterior bones of the
suspensorium are shortened and more vertically oriented. All of these
features are necessitated by the increase in mouth size without a cor-
responding isometric increase in the length of the skull.

COMPARISON OF Microgobius wrrH RELATED GENE:RA OF AMERICAN
SEVEN-SPINED GOBIES ( FIG 14 ).-I have not attempted to examine each
of the genera in detail. The genera Bollnumnia and Parrella, allied with
Microgobius by Ginsburg ( 1939: 37), were. most closely examined.
Palatogobius, allied to Microgobius by Gilbert ( 1971: 33); Gobiosoma,
the large genus indicated to be the basal group for most of the American
seven-spined genera by B6hlke and Robins ( 1969); and the divergent
genera Evermannichthys and Pariah were compared with Microgobius,
based on limited cleared and stained material and radiographs. The
genera Chriolepis, Psilotris, Various, Gobulus, Pycnomma, Gymneleotris,
Eleotrica, Barbulifer, Enypnias, and Aruma were examined only from
radiographs; and Nes, Risof, and Ginsburgellus were not examined.

Table 3 shows a comparison of Microgobius, Bollmannia, Parrellci,
Palatogobius, and Gobiosoma for 15 osteological characters. Gobiosoma
is used in this discussion as defined by B6hlke and Robins ( 1968: 53)
and not according to the more limited deBnition of Hoese ( 1971, un-
published dissertation).

B6hlke and Robins ( 1968, 1969) suggested that 15 of the 20 American
seven-spined genera were derived from Gobiosoma, excluding only Mi-
crogobius, Bollmannia, Parrella, and the subsequently described Palato-
gobius ( these four genera will be referred to hereafter as the Microgo-
bius group). Hoese ( unpublished dissertation), though differing with
the generic concepts and relationships within the Gobiosoma group as
proposed by B6hlke and Robins, agrees that the Microgobius group does
not appear to be closely related to the Gobiosoma group.

The Gobioso,na group is distinctive in having hypurals 1-2 fused
with hypurals 3-4 and the urostyle, a feature that is both rare and speci-
alized in gobioids. Examination of this feature in representatives from



174 
B

U
LLE

TIN
 FLO

R
ID

A STATE M
U

SEU
M
 

Vol. 19, N
o. 3

TABLE 2.--OSTEOLOGICAL TRENDS WITHIN THE GOBIOIDEI.

Character Generalized condition Most frequent condition Most specialized condition

1 Frontal bones N6 median crest; not fused; No median crest; fused; narrow Formed into median crest;
broad between the orbits between the orbits fused; narrow between the

orbits

2 Median ethmoid No formation of interocular Interocular septum present Interocular septunn present
septunn

3 Teeth on vomer Present Absent ' Secondarily developed ?

4 Parasphenoid No transverse shelf for attach- Transverse shelf for attachment Transverse shelf for attachment
ment of rectus muscles of rectus muscles of rectus muscles

5 Intercalar Well developed Moderately developed Absent

6 Cephalia sensory canals Supported by open troughs Supported·by open Enclosed in bony tubes
troughs

7 Lacrymal Well developed Moderately developed Poorly developed ( unossiBed)

8 Infraorbital bones 1 present in a few species Absent Absent



1975 
B

IR
D

S
O

N
G

: M
IC

R
O

G
O

B
IU

S
 SIG

N
ATU

S O
STEO

LO
G

Y 
175

TABLE 2 ( CONTINUED )

Character Generalized condition Most frequent condition ~ Most specialized condition

9 Supratemporal bones 2-3 present in a few species Absent Absent

10 Preopercle Well developed symplectic Variable No symplectic process
process

11 Mesopterygoid Present Absent Absent

12 Metapterygoid Broad, overlapping quadrate Variable Narrow, greatly reduced and
widely separated from quadrate

13 Basihyal Spatulate Variable Narrow or bifid

14 Epihyal Sutured to ceratohyall Not sutured to ceratohyal Not sutured to ceratohyal

15 Branchiostegal rays 6-7 5 4 ( according to Takagi,
unpublished, M.S.)

16 Posttemporal bone Well developed dorsal and Well developed dorsal and Ventral arm unossifled or
ventral arms ventral arms absent (?')

17 Dorsal postcleithrum Present Absent Absent

18 Ventral postcleithrum Present Present Absent

19 Scapula Well ossifed, enclosing scapular Partly ossified, not enclosing Unossified or apparently fused
foramen , scapular foramen to cleithrum in sorne



176  
B

U
LLE

TIN
 FLO

R
ID

A
 STATE M

U
SEU

M
 

Vol. 19, N
o. 3

TABLE 2 ( CONTINUED ~

Character Generalized condition Most frequent condition Most specialized condition

20 Pectoral radials (Ossifed) 4 4 3

21 Position of pelvic spine In line with pelvic rays In advance of pelvic rays In advance of pelvic rays

22 Number of pelvic rays 5 5 0

23 Vertebral number 25-33 25-37 60+

24 Epipleural ribs Articulating with pleural ribs Articulating with pleural ribs Fused to pleural ribs or absent

25 Pleural ribs Present on all precaudal verte- Present on all precaudal verte- Absent
brae except the first two brae except the first two

26 Spinous dorsal Number of pterygiophores Number of pterygiophores Accessory spines developed
pterygiophores equals number of spines equals number of spines without pterygiophores or

spines lost with
pterygiophores retained

27 Epurals 2-3 1-2 1

28 Hypurals 1-2 Articulate with urostyle Articulate with urostyle Fused to urostyle

29 Parhypural and hypural 5 Small, with a cylindrical core Small, with a cylindrical core Minute, without a cylindrical
core; apparently absent in some

i Seen only in large individuals



1975 
B

IR
D

S
O

N
G

: M
IC

R
O

G
O

B
IU

S
 S

IG
N

ATU
S
 O

STEO
LO

G
Y 

177

TABLE 3.-COMPARISON OF MICROGOBIUS WITH SOME RELATED GENERA IN SELECTED OSTEOLOCICAL CHARACTERS,

Character Microgobius BoUmannia Pan"Ua Palatogobiusl Cobiosoma

Bony support of Canal supported Portions of canal Canal supported Canal supported Variable, open troughs
supraorbital by an open trough enclosed in bony by an open trough by an open trough in some species, en-
sensory canal tube (S)2 closed in bony tube in

others (S)

Position of frontal Overlaps median Barely reach me- Overlaps median Overlaps median Overlaps median
bones in relation to ethmoid dian ethmoid (S) ethmoid ethmoid ethmoid
median ethmoid

Transverse crest on Present Present as part Present, but Present, but Present, sometimes as
frontal bones of bony tube reduced greatly reduced part of bony tube

Sagittal crest on Present (S) Present (S) Absent Absent Absent
frontal bones

Basihyal shape BiEd (S) Spatulate Bind (S) Narrow Spatulate

Teeth on vomer Absent Absent Absent Present ( at Ieast in Absent
holotype)



TABLE 3 (CONTINUED )
178  

B
U

LLE
TIN

 FLO
R

ID
A STATE M

USEUM
 

Vol. 19, N
o. 3

Character Microgobius BoUmannia Parrella Patatogobiusi Gobiosoma

Process on metaptery- Absent (S)2 Absent (S) Absent (S) Absent Present
( metapterygoidgoid overlapping

quadrate greatly reduced)
(S)

Symplectic process on Slightly developed Slightly developed Absent (S) Present Present
preopercle to absent (S) to absent (S)

Ossified nasal bones Present Present Present Absent (S) Absent in some
5pecies (S)

Lateral shelves on Absent (S) Present Present Present One shelf present,

posttemporal (two shelves) ( one shelf) ( one shelf) but reduced

Sphenotic shape Short Short Short Short Elongate in some (S)

Ventral postcleithrum Absent (S) Present Absent (S) Present Absent (S)

Hypurals 1-2 fused to No No No No Yes(S)
hypurals 3-4 and to
urostyle

Shape of brain case Circular Circular Circular Circular Elongate
in dorsal view

Fused frontal bones Yes (S)2 Yes(S) Yes ? (S) No Yes(S)

1 This genus is known only from the hdotype and two other specimens that differ from the holotype in lacking vomerine teeth. The

possibility exists that the non-type specitnen examined in this study is not conspecific with the holotype.
2 (S)= those character states that appear to be specialized.



1975 BIRDSONG : MICROGOBIUS SIGNATUS OSTEOLOGY 179

4 subgenera of Gobiosoma and 9 derived genera showed the only excep-
tion to the fused condition of the caudal to be in Gobiosoma polyporo-
sum ( = G. etheostoma according to Hoese, unpublished dissertation ).
On the basis of other characters, Dawson ( 1969: 514) suggested this
species to be one of the most primitive members of Gobiosoma.

The absence of the fused caudal condition in the Microgobius group
suggests a more primitive origin for these genera and essentially excludes
any of the Gobiosoma lineages from their ancestry. Conversely, speciali-
zations (?) occurring in Microgobius, Bollmannia, Parrella, and Palato-
gobius appear to exclude each of these genera from the ancestry of each
other ( see Table 3).

Understanding of relationships is greatly impaired by the difficulty of
discerning specialized trends in small groups such as these being con-
sidered, and by the lack of understanding of the lability of most of the
characters. Since many of the osteological character states here com-
pared represent seemingly minor modifcations, it is by no means certain
that the trends within the American seven-spined gobies follow the ap-
parent trends seen in gobioids in general. For example, fusion of the
frontal bones appears to be a common, though specialized, condition in
gobioids; however, in many small gobioids separate frontal bones appear
to be correlated with an overall reduction in ossification and in these
groups the separate frontals may represent a specialized condition.
Likewise, the vomerine teeth of Palatogobius may be a de nouo develop-
ment. In the absence of strong contrary evidence, however, those char-
acter states appearing to be generalized within gobioids are assumed to
be generalized within the American, seven-spined gobies.

Of the 15 osteological characters compared in Table 3, Palatogobius
possesses fewer specializations (2) than any of the other American seven-
spined genera examined, and also shares the fewest specialized features
with the other genera. Specialized features are distributed among the
other genera as follows: Microgobius (7), Bollmannia (6), Parrella (5),
and Gobiosoma (6). On the basis of shared specialized osteological
features, the closest relation appears to be between Microgobius and
Parrella with five shared specializations, followed by Microgobius and
Bollmannia with four, and Bollmannia and Parrella with three. Micro-
gobius, Parrella, and Bollmannia each share three specializations, though
not the same three features, with the Gobiosoma group and one special-
ization with Palatogobius. From this evidence it appears that Micro-
gobius, Parrella, and Bollmannia are more closely related to each other
than to the Gobiosoma group, and Palatogobius is possibly more primi-
tive than any of these groups and somewhat removed from them phylo-
genetically.



180 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

VALIDITY OF THE AMERICAN SEVEN-SPINED GOBY GROUP.-All of the

American seven-spined goby genera examined ( except Et)ermannichthys
and Pariah, discussed separately below) share the following osteological
features: 11 precaudal vertebrae; 16 or 17 caudal vertebrae; a spinous
dorsal Bn formula of 3( 221110); an unossified scapula; and the insertion
of the first two anal pterygiophores anterior to the first haemal spine.
They further share, along with many other gobioids, those character
states given as the "most frequent condition" in Table 2. for the characters
numbered, 2, 4, 5, 7, 8, 9, 11, 14, 15, 16, 17, 20, 21, 22, 23, 24, 25, 26, 27,
and 29.

The most bonvincing evidence for considering the American seven-
spined gobies a natural assemblage is the shared features of 11 + 16 - 17
vertebrae and the 3(221110) pterygiophore pattern. Vertebral number
and pterygiophore pattern are extremely stable characters within many
groups of gobioids. For example, in the examination of radiographs of
over 250 specimens of Microgobius only five specimens varied from the
typical condition in these two characters. Furthermore, the combination
of 11+16 vertebrae and 3(221110) pterygiophore pattern is virtually
unique to the American seven-spined group.

In the examination of dorsal fin characteristics and vertebral number
of over 400 species of gobioids from around the world, only one species
from outside the Americas has been found with a pterygiophore pattern
of 3( 221110). This species, Tukugobius carpenteri from the Philippines,
also possesses 11 precaudal vertebrae, a vertebral number uncommon in
other than the American seven-spined genera. The pterygiophore num-
ber and arrangement in T. carpenteri is constant, though in many speci-
mens the last Di spine is absent. The occurrence of two epurals in T.
carpenteri is the only gross osteological characteristic distinguishing it
from the American seven-spined genera. The importance of two epurals
versus one epural is difficult to assess at this time, and the relationship
of T. carpenteri to the American seven-spined gobies must remain in
question.

The genera Evermannichthys and Pariah, allied with the seven-spined
genus Risor by B6hlke and Robins ( 1969: 14) and B6hlke ( 1969: 3),
differ from the seven-spined genera in having 12-15 precaudal vertebrae,
17-20 caudal vertebrae, and either a variable number of dorsal spines
(3-7 in Evermannichthys) or 8 dorsal spines ( in Pariah). Examination
of limited material of Pariah ( 7 specimens) reveals a constant Di formula
of 3( 2211110) and 12+ 17 vertebrae. This condition differs from that
of the seven-spined genera only in the addition of one precaudal vertebra
and ifs associated pterygiophore and spine.

Evermannichthys shows considerable inter- and intraspecific variation



1975 BIRDSONG : MICROGOBIUS SIGNATUS OSTEOLOGY 181

in pterygiophore pattern, number of dorsal spines, and number of verte-
brae. E. metzelaari varies from 3 to 7 in number of dorsal spines ( B6hlke
and Robins 1969). My examination of a single specimen showed a D1
formula of 4 ( 21111101) and 15 + 20 vertebrae. In 2 specimens of E.
convictor the Di formulae were 4( 211I10) with 13+ 17 vertebrae and
3( 2111110) with 13+ 18 vertebrae. In 7 specimens of E. silus, two were
3(121110) with 12+17 vertebrae, three were 3(1211110) with 13+17
vertebrae, one was 3( 1211101) with 13 + 17 vertebrae, and one was
3( 122111) with 12 + 17 vertebrae. The extreme variability of these
characters in Evermannichthys makes interpretation difficult, and con-
sequently adds little information to the validity of their placement with
the seven-spined genera. Bohlke and Robins ( 1969: 13) have pointed
out that Risor, Pariah, and Evermannichthys, all sponge dwelling gobies,
seem to form a natural progression from the Gobiosoma ( Tigrigobius)
line, with Evermannichthys being the most highly specialized for this
mode of life. These two genera also share with Gobiosoma and its de-
rivatives the feature of having hypurals 1-2 fused to hypurals 3-4 and
the urostyle. It is perhaps significant that these reductions in the num-
ber of dorsal spines and/or increases in variability in the spinous dorsal
fin and an increase in vertebral number are similar to the modifications
seen in other genera of hole dwelling or burrowing gobies ( e.g., Chloea,
Cleuelandia, Clariger, Typhlogobius, Luciogobius, Ilypnus, Inu, and
others). Considering all of the evidence, it appears that Everman-
nichthys and Pariah are indeed properly placed with the Gobiosoma
group of American seven-spined gobies.

Recently, Miller and Tortonese ( 1968: 355) have suggested an align-
ment of the six-spined Mediterranean gobiid Odondebuenia balearica
with the American seven-spined genera based upon similarities in squa-
mation and sensory pore and free neuromast patterns. I have not exam-
ined Odondebuenia, but its six-spined condition, combined with the
present difficulty of interpreting the phylogenetic significance of sensory
pore and neuromast patterns in gobioids, leaves the alignment of this
genus with the American seven-spined gobies in doubt.

Nominal gobioid families are presently poorly defined, some poorly
conceived, and all in a considerable state of systematic disorder. Con-
siderable caution is therefore dictated in the erection of new taxa above
the species level. The American seven-spined gobies, however, do appear
to be a natural assemblage of species, defined by those characters given
in this discussion, and worthy of more formal designation. The American
seven-spined gobiids are here designated as the tribe Gobiosomini of
the family Gobiidae, containing the genera given below. Recognition of
the group at the tribal level is conservative, though somewhat arbitrary,



182 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

and provides a less cumbersome reference than does "American seven-
spined gobies."

FAMILY GOBIIDAE

GOBIOSOMINI, new tribe

Gobiosolna Girard 1858 Various Robins and B6hlke 1961
Nes Ginsburg 1933 Chriolepis Gilbert 1892
Amma Ginsburg 1933 River Ginsburg 1933
Eleotrica Ginsburg 1933 Evermannichthys Metzelaar 1919
P!/cnomma Rutter 1904 Pariah B6hlke 1969
Cumneleotris Bleeker 1874 Ginsburgellus Bahlke and Robins 1968
Enimnias Jordan and Evermann 1898 Microgobius Poey 1876
Bat·butifer Eigenmann and Eigenmann Parrella Ginsburg 1939

1888 Bolimannia Jordan 1890
Gobulus Ginsburg 1933 Palatogobius Gilbert 1971
Psilotris Ginsburg 1953

ADDmONAL COMMENTS ON MILLER'S CLASSIFICATION OF GOBIOIDS.-

In establishing the Tribe Gobiosomini it seems appropriate to discuss
the recent classification of gobioids proposed by Miller ( 1973). Miller's
classification is as follows:

Family Rhyacichthyidae, monotypic
Family Gobiidae, 2,000 t species

Subfamily Eleotrinae, 40 genera
Subfamily Pirskeninae, monotypic ( fossil)
Subfamily Xenisthminae, monotypic
Subfamily Gobionellinae, 20 genera
Subfamily Tridentigerinae, 2 genera
Subfamily Gobiinae, 200 (?) genera
Subfamily Kraemeriinae, 4 genera

Miller further divides the Gobiinae into six tribes. Though the tribes
were not deftned, it is apparent that the Tribe Gobiosomini, as here
conceived, constitutes a part of Miller's Tribe Gobiini.

The placement of all gobioids ( except Rhyacichthys) into one family
appears to lack a great deal in utility and mask the diversity of the
group. Further, Miller's justification for this lumping seems faulty.
He implies that the classificational heirarchy of the teleosts dictates that
gobioids be placed in only two families, but I find as much diversity of
form and habit among the gobioids as there is among the percoids, a
group divided into 71 families by Greenwood et al. ( 1966). Miller also
reasons that "on the basis of presumed geological age, we may equate
the entire suborder Gobioidei with a subfamily of insecta, and view the
gobiid subfamilies as tribes ..... I see no utility in attempting to
equate higher taxa of fishes with taxa of insects. If this reasoning is



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 183

followed, I presume we must then equate the Teleostei with the carabid
beetles, the two groups being of approximately the same size, geological
age and ecological diversity; and reduce the teleosts to a single family!

My primary concern with Miller's classification is more basic than
the assignment of taxonomic level, however, and is directed toward the
definition of the groups and the implied phylogeny. The following
characters were used by Miller in defining the groups: (1) number of
epurals; (2) number of branchiostegals; (3) presence of mesopterygoid;
(4) presence of an upper postcleithrum; (5) presence of a scapula; (6)
presence of supratemporals; (7) nature and extent of the metapterygoid
connection to the quadrate; (8) connection of the preoperculum to the
symplectic; ( 9) number of pectoral radials; ( 10) fusion of the hypurals;
( 11) position of the anteriormost supraorbital ( oculoscapular) sensory
canal pore; and ( 12) number of preopercular sensory canal pores.

The occurrence and lability of most of these characters have been
commented upon in the preceding discussion. Characters 11 and 12
( above), features of the cephalic sensory canal system, require comment
here. Character 11 is difficult to evaluate in the form used by Miller.
Essentially, it involves two character states, the anterior pore being
situated either before the anterior nostril or behind the anterior nostril.
I have no information on the lability of this feature, but the assignment
of a character state is as much dependent upon the position of the
anterior nostril as upon the position of the pore, thus rendering the char-
acter ambiguous at best. The number of preopercular canal pores
( character 12 above) is an especially labile feature in gobioids. Though
there is a general tendency for eleotrids to have more preopercular pores
(given as «up to 5" by Miller), the vast majority of gobioids possess
either 2,3, or none, with abundant evidence that reduction of the pre-
opercular pores has occurred numerous times within gobioids.

Though no list of species examined is given, it is apparent that a por-
tion of the problems with Miller's classification stems from being based
on a relatively small sample of the gobioids. I can think of no other
explanation for his tendency to place intermediate forms into separate
subfamilies ( e.g., Xenithminae and Tridentigerinae). Other intermediate
forms exist that would appear to be as worthy of subfamilial status as
these two. For example, the Xenithminae differ from the Eleotrinae by
the loss of the upper postcleithrum and the mesopterygoid. Gobiomor-
phus would then seem to be worthy of subfamily recognition since it
differs from the Eleotrinae by the loss of the mesopterygoid and the
fusion of the epurals, and from the Xenithminae by the fusion of the
epurals and the loss of the supratemporals.

Other forms, such as Chasmichthys dolichognathus, with two epurals,



184 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

a symplectic process on the preoperculurn ( as in the Tridentigerinae),
and a broad metapterygoid connection to the quadrate ( as in the
Eleotrinae) yield problems, as does Luciogobius guttatus with two
epurals and a quadrate process on the metapterygoid ( as in the Tri-
dentigerinae ), but without a symplectic process on the preoperculum
(as in the Gobionellinae and some Gobiinae ). I have little doubt that
a broader survey of gobioids would further erode the concept of several
of Miller's subfamilies. Miller says ( p. 420) that "since none of these
groups [subfamilies of Gobiidae] possesses all the primitive characters
occurring within the family, traditional raising of the Eleotrinae, or any
of the other subfamilies, to separate family rank would involve arbitrary
division of the series on merely one of several skeletal criteria. How-
ever, this has obviously not been applied in his erection of subfamilies.

Miller's reliance on the retention or loss of a few primitive, simple,
and probably somewhat labile osteological features in his classification
appears to greatly influence his view of gobioid evolution. The follow-
ing passage ( p. 420) is Miller's most concise 5tatement of his view of
gobiid phylogeny: "Despite a gradually increased skeletal specializa-
tion through these gobiid subfamilies, there seems little evidence that
one is very much older than any other as a separate line, and they must
therefore rank equally in a system intended to demonstrate phylogeny.
Their disparity in structure and extent of specialization thus may be
interpreted as reBecting differences in rate of evolution since their origin
as separate phyletic lines in a period of explosive radiation from early
gobiid stock." I find Miller's phyletic "sunburst" most unsatisfying and
optimistically believe that further evidence will reveal a more cladistic
picture of gobioid evolution.

Though it may seem appropriate for this criticism of Miller's classiB-
cation to be accompanied by an alternative proposal, I have resisted this
temptation. Less than one percent of the described species have re-
ceived detailed osteological examination. New information is being ob-
tained at an increasing rate, and it appears to me prudent to live a while
longer with the imperfect classification that exists.

LITERATURE CrrED

Akihito, Prince. 1963. On the scapula of gobiid fishes. Japanese Jour. Ichthyology,
11(.1-2): 1-26 (in Japanese).

1967. Additional research on the 5capula of gobiid fishes. Japanese
Jour. Ichthyology, 14( 4-6): 167-181 ( in Japanese).

1969. A systematic examination of the gobiid fishes based on the
mesopterygoid, postcleithra, branchiostegals, pelvic fins, scapula and suborbitals.
Japanese Jour. Ichthyology, 16(3): 93-144 ( in Japanese).

B6hlke, J. E. 1969. Parish scotius, a new sponge-dwelling gobiid fish from the
Bahamas. Notulae Naturae, No. 421: 1-7.



1975 BIRDSONG: MICROGOBIUS SIGNATUS OSTEOLOGY 185

and C. R. Robins. 1968. Western Atlantic seven-spined gobies, with
descriptions of ten new species and a new genus, and comments on Pacific rela-
tives. Proc. Acad.

1969. Western Atlantic sponge-dwelling gobies 6f the
genus Evermannichthys: their taxonomy, habits and relationships. Proc. Acad.
Nat. Sci. Phila., 121 (1): 1-24.

Dawson, C. E. 1968. Eastern Pacific wormfishes, Microdesmus dipus Gunther and
Microdes,nus dorsipunctatus sp. nov. Copeia, 1968( 3): 512-531.

1969. A new seven-spined goby, Gobiosoma C Austrogobius) pok/poro-
sum, from the Pacific coast of Panama. Copeia, 1969( 3): 510-514.

Freihofer, W. C. 1970. Some nerve patterns and their systematic significance in
paracanthopterygian, salmoniform, gobioid, and apogonid fishes. Proc. California
Acad. Sci., Ser. 4, 38( 12): 215-264.

Gilbert, C. R. 1971. Two new genera and species of western Atlantic gobiid fishes
with vomerine teeth. Copeia, 1971 (1): 27-38.

Ginsburg, I. 1939, Twenty-one new American gobies. Jour. Washington Acad.
Sci.,29(2): 51-63.

Gostine, W. A. 1955. The osteology and relationships of certain gobioid fishes, with
particular reference to the genera Kraemeria and Microdesmus. Pacific Sci.,
9( 2): 158-170.

Gregory, W. K. 1933. Fish skulls: a study of evolution of natural mechanisms.
Trans. Amer. Phil. Soc., 23(2): 75-481.

Greenwood, P. H. et at. 1966. Phyletic studies of teleostean fishes, with a provi-
sional classification of living forms. Bull. Amer. Mus. Nat. Hist., 131 (4):
341-455.

HoESE, D. F. 1971. A revision of the eastern Pacific species of the gobud Esh genus
Gobiosoma, with a dikcussion of relationships of the genus. Uhpublished Ph.D.
dissertation, Univ. California, San Diego, 213 pp.

Johnson, D. R. 1969. The axial osteology of the goby, Quisquitius eugenius
( Jordan and Evermann ). Japanese Jour, Ichthyology, 16( 2): 83-85.

Jordan, D. S. and C. H. Eigemann. 1886. A review of the Gobiidae of North
America. Proc. U.S. Nat, Mus., 9: 477-518.

Lele, S. H. and R. D. Kulkarni. 1938. The skeleton of Periophthalmus barbarus
(Linn.) (I). The skull. Jour. Univ. Bombay, 6(5): 76-91.

1939. The skeleton of Periophthalmus barbarus ( Linn.).
( II). Branchial arches, vertebraI column and appendicular skeleton. Jour.
Univ. Bombay, 7(5): 123-134.

Matsubara, K. and T. Iwai. 1959. Description of a new sandfish, Kraemeria sex-
radiata, from Japan, with special reference to its osteology. Jour. Washington
Acad. Sci., 49( 1): 27-32.

McAllister, D. E. 1968. Evolution of branchiostegals and classification of telestome
fishes. National Museums of Canada, Bull. 221, Biol. Ser. No. 77, 239 pp.

Miller, P. J. 1963. Taxonomy and biology of the genus Lebetus C Teleostei, Cobi-
oidea ). Bull. British Mus. ( Nat. Hist. ) Zool., 10( 3): 205-256.

1973. The osteology and adaptive features of Rhyacichthys aspro
( Teleostei: Gobioidea) and the classification of gobioid fishes. Jour. Zool.,
London, 1973( 171): 397-434.

and E. Tortonese. 1968. Distribution and systematics of the gobiid fish
Odontdebuenia balearica C Pellegrin and Fage). Ann. Mus. Civ. Stor. Nat.
Genova, 77: 342-359.

Monod, T. 1968. Le complexe urophore des poissons teleosteens. Mem. Inst.
Fondamental D'Afrique Noire, No. 81, 705 pp.

Regan, C. T. 1911. The osteology and classification of the gobioid fishes. Ann.
and Mag. Nat. Hist., Ser. 8, 8( 48): 729-733.

Rosen, D. E. and C. Patterson. 1969. The structure and relationships of the para-
canthoptefygian fishes. Bull. Amen Mui Nat. Hist., 141(3): 357-474.



186 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 3

Springer, V. G. 1968. Osteology and classification of the fishes of the family
Blenniidae. U. S. Nat. Mus., Bull. 284, 85 pp.

Starks, E. C. 1901. Synonomy of the fish skeleton. Proc. Washington Acad. Sci.,
3: 507-539.

Takagi, K. 1950. On the glossohyal bone of the gobioid fishes of Japan with some
phylogenetic considerations. Japanese Jour. Ichthyology, 1(1): 37-52 (in
Japanese).

Taylor, W. R. 1967. An enzyme method of clearing and staining small vertebrates.
Proc. U.S. Nat. Mus., 122( 3596): 1-17.

TeWinkel, L. E. 1935. A study of Mistichthys luzonensis with special reference to
conditions correlated with reduced size. Jour, Morph., 58: 463-509.



KEY TO A~BREVIATIONS

ANC-angular MX PAL-maxillary process of palatine
AR PMX-articular process of premaxilla N-nasal
ART-articular NA-neural arch
ASC PMX-ascending process of pre- NC-neural canal

maxilla NS-neural spine
BB-basibranchial OP-opercle
BH-basihyal PAL-nalatine
BO-basioccipital PAP-parapophysis
BR-branchiostegal PB-pharyngobranchial
BTP-branchial tooth patch PC-procurrent cartilage
C--centrum PHYP-parhypural
CB-eratobranchial PM PMX-postmaxillary process of pre-
CH-ceratohyal maxilla
CL-cleithrum PMX-premaxilla
COR-coracoid POP-preopercle
COR D-coronoid process of dentary PPTG-proximal radial
D-dentary PR-pleural rib
DH-dorsal hypohyal PRO-prootic
DPTG-distal radial PS-parasphenoid
EB-epibranchial PT-ectopterygoid
EH-epihyal PTG-pterygiophore
EO-exoccipital PTM-posttemporal
EPO-epiotic PTO-pterotic
EPR-epipleural rib PTS-pterosphenoid
EPU-epural PZP-prezygapophysis
ETH PAL-ethmoid process of palatine QU-quadrate
F-frontal RAD-pectoral radials
FIG-foramen for internal carotid drtery RC-rostral cartilage
GR-gillraker SCA-scapular cartilage
HB-hypobranchial SCI-supracleithrum
HS-haemal spine SES-sesamoid articular
HYO-hyomandibular SOC-supraoccipital
HYP-hypural SOP-subopercle
IH-interhyal SPH-sphenotic
INT-intercalar STF-subtemporal fossa
IOP-interopercle SYM-symplectic
L MX-lateral head of manila UH-urohyal
LAC-lacrymal UPT-upper pharyngeal tooth plate
LE-lateral ethmoid US-urostyle
LPT-lower pharyngeal tooth plate V-vomer
M MX-medial head of maxilla VH-ventral hypohyal
ME-medial ethmoid VT-vertebra
MPT-metapterygoid V-foramen for trigeminal nerve
MPTG-medial radial VII-foramen for facial nerve
MX-maxilla

ABBREVIATIONS USED AS ORIENTATION GUIDES :

A, anterior; D, dorsal; L, lateral; M, medial; P, posterior; V, ventral; EX, ex-
terior; IN, interior.



Contributions to the BULLETIN OF THE FLORIDA STATE MUSEUM, BI-
OLOGICAL SCIENCES SERIES, may be in any field of biology. Manuscripts
dealing with natural history or systematic problems involving the southeastern United
States or the New World tropics are solicited especially. Manuscripts should be of
medium length-irca 35 to 200 pages ( 10,500-16,000 words). Examination for
suitability is made by an Editorial Board.

The BULLETIN is distributed worldwide through institutional subscriptions and
exchanges. It is considered the responsibility of the author to distribute his paper
to all interested individuals. To aid in this the author( s ) receive( s) 50 copies free,
and he may purchase additional separates at cost if ordered when page proof is re-
turned. The author is also responsible for any charges incurred for alterations made
by him on galley or page proofs. The Museum will send an invoice to the author
for this amount upon completion of publication.

PREPARATION OF MANUSCRIPT

Contributors should consult recent numbers of the BULLETIN for preferred style
and format. Highly recommended as a guide is the CBE Style Manual, 3rd Edition,
1972 ( Washington, D.C., Amer. Inst. Biol. Sci.).

MSS must be submitted in duplicate ( please no onionskin) and satisfy the follow-
ing minimal requirements: They should be typewritten, double-spaced ( especially
tables, figure captions, and "Literature Cited"), on one side of numbered sheets of
standard (8-1/2 x 11 in.) bond paper, with at least one-inch margins all around.
Tables ( which should be unruled) and figure legends should be typed on separate
sheets. All illustrations are referred to as Egures. They must comply with the
following standards: Photographs should be sharp, with g6od contrast, and printed
on glossy paper. Drawings should be made with dense black waterproof ink on
quality paper or illustration board. Ali illustrations should have a cover sheet. All
lettering will be medium weight, san-serif type ( e.g., Futura Medium, News Gothic)
in cutout, dry transfer, or lettering guide letters. Make allowance so that after re-
duction no lowercase letter will be less than 1 mm high (2 mm is preferred) nor
any capital letter greater than 5 mm. high. The maximum size for illustration is
8-5/8 x 14 in. ( twice typepage size); illustrations should not be less than typepage
width ( 4-5/16 in.). Designate the top of each illustration and identify on the back
with soft pencil by author's name, MS title, and figure number.

Manuscripts and all editorial matters should be addressed to:

Managing Editor of the BULLETIN
Florida State Museum
Museum Road
University of Florida
Gainesville FL 32611