Riri'ra Irllirna di Paleonrologir e Strarigrr l;-;l *;;,r SHORT NOTE - NOTA BREVE METAXYTHERIUM MEDIUM (MAMMALIA: SIRENIA) FROM UPPER MIOCENE SEDIMENTS OF THE ARENARIA DI PONSANO FORMATION (TUSCANY, ITATY) GIOVANNI BIANUCCI S{ \TALTER LANDINI Receioed March 19,2AA2; accepted Marcb 2g,20A3 Key raords: Mammalia, Strenia, MetaxVtberium med,ium, System- atics, Late Miocene, Tuscany, Italy. Abstract, Records of Metaxytherium medium (Mammalia: Si- renia) from Tortonian (Late Miocene) sediments from the Arenaria di Ponsano Formation (Tuscany, ftaly) are described. They consist of fragmentary specimens, including several partìal cranial elements rep- resenting at least three skulls, two humeri, fraqments of vertebrae and some incomplete ribs. The neu, Tuscan records confirm the wide diffu- sron of Metaxytherìum in the Mediterranean during the Miocene. This sirenian's occurrence in the Arenaria di Ponsano sediments is in accor- dance with the shelf environmenr indicated by other fossils. The low sea botton was at least parrially covered by segrass meadows, the food source of this dugongid. Riassunto. Vengono descritti resît di Metaxytheriam medium (Mammalia: Sirenìa) provenienri dai sedimenti tortoniani (Miocene superiore) dell'Arenaria di Ponsano (Toscana, Italia). Si tratta di re- perti fr.rmmentari rappresentati prevalentemente da diversi elementi craniali appartenenti almeno a tre distinti crani, due omeri, frammenti di vertebre e alcune coste incomplete. Questa segnalazione conferma I'ampia diffusio ne di Metaxytherium nelMedtterraneo duranre il Mioce- ne. Il ritrovamento di sirenia nei sedimenti dell'Arenaria di ponsano è in accordo con l'ambiente di piattaforma indicato anche dagli altri fos- sili. Il basso fondale marino era almeno in parte ricoperto da praterie algali, la sorgenre di cibo di questo dugongide. Introduction Metaxytberium is an extinct dugongid sirenian that shows a wide geographical and biostratigraphical distribution. In fact, Metaxytherium rernains have been collected in several Early-Late Miocene localities of the Mediterranean region (see below; summary in Domn- ing & Thomas 1,987), northern France (Corrreau 1928), North and South America (Muizon Br Domning 1985; Domning 1988; Aranda-Manreca et aL. 1994), and al- so in Pliocene sedimenrs of the Mediterranean Basin (Domning & Thomas 1987). The Miocene specimens from Mediterranean and adjacent areas were collected mainly from Central and tVestern Paratethyan depos- its of Austria and Switzerland (Domning & Pervesler 2001), from Spain (Pilleri er al. 1989), and from many localities of southern Italy and Sardinia (Moncharmot Zeí t< Moncharmont 1986; Carone 1997; Bianuccr et al. 2003). New specimens referred to Metaxytheriwm mediwm, collected rn 1965 by Dr. Angelo Varola from Tortonian sediments of the Arenaria di Ponsano Formation near Volterra (Tuscany, Central ltaly) (Fig. 1), are described in this paper. The sirenian remains examined here belong to an undescribed collection of marine mammals, containing also odontocete and mysricere specimens kept in the Museo di Storia Naturale e del Territorio (MSNT) of the University of Pisa. Anatomical terminology follows Domning (1988). Systematic description. Class Mammalia Linnaeus, 1258 Order Sirenia Illiger, 181 1 Family Dugongidae Gray, 1821. Subfamily Halitheriinae (Carus, 1868) Abel, 1913 Genus Metaxytberiun de Christol, 1840 Metaxytherium medium (Desmarest, 1822) Hooije r, 1952 (Figs.2-5; Pls. 1,2) Dipartimento di Scienze della Terra, via S. Maria, 53,I-56126 Pisa (Italy). E-maìl: bianucci@dst.unipi.it; landini@dsr.unipi.it. 568 Referred specimens. Several fragments belonging to at lerst three animals; among these the most significant parts are two skull roofs (MSNT I10140; MSNT I10095), one right zygomatic process of the squamosal and the associated jugal (MSNT 10068), right (MSNT 110141) and left (MSNT 110138) humeri probably of the seme anìmal, a fragment of a right scapula (MSNT I10148), and some incomplete r-ertebrae and ribs. Description Frontal - The dorsal surface of the preserved pos- rerior portion of the frontals of MSNT I1 0095 is flat and narrow and it is laterally delimited by rounded and slightly laterally concave temporal crests (Fig. 2;PI. 1,, fig. 2) . The crests are separated by a distance of at least 27 mm. Parietal - Temporal crests on the parietal roof of MSNT 110140 correspond to the "type E" morphology described by Domning (19S8) for Metaxytheriwmflorìda- num (Fig.3; P1. 1, fig. 1). They are prominent and lyri- form and they come closest to the midline (12 mm) about Fig. 2 - Skull roof (MSNT 110095) in dorsal vìew of Metaxytberium mecLíum from the Arenaria di Ponsano Formation. Fig. 1 - Geographic location of the Arenaria di Ponsano Fonna- rion wlrere rhe.irenirn spe- cimens examined in this paper were collected. The numbers refer to the fossiliferous out- crops (moclìfied from Menesi- ni 1967a). 55 mm anterior to the nuchal crest. The median valley be- tween these temporal crests is concave and about 14 mm deep. In MSNT 10095, the temporal crests are less promi- nent and there is not a deep median valley. The crests of this specimen are of the "type A' of Domning (1988). The parietal roofs of the Po:-rsano specimens are narrower than in any of the specimen s of M. floridanum. Internally, the parietal of MSNT I10140 exhibits an evident bony falx cerebri that runs anteroposteriorly from the frontoparietal suture to the internal occipital protuberance. Supraoccipital - This bone is entirely preserved in MSNT 110140 and partially in MSNT 110095. In lateral view, the supraoccipital of MSNT I10140 forms an an- gle of about 125'with the parietal roof. The nuchal crest is relatively rounded and the external occipital protuber- ance rises above plane of parietal roof, and below it, the median ridge separates two evident rugose semispinalis muscle insertions. The supraoccipital-exoccipital sutures form an angie of about 145". Jugal - The jugal (MSNT I10148) is laterally broad and triangular, and it has straight posteroventral and an- teroventral margins forming an angle of about 100" (Fig. 4; Pl. 1, fig. 3). The ventral tip of the jugal is located un- der the orbit. Squamosal - Only an anterior fragment of a left zygomatic process is preserved (MSNT 10068). The sq- uamosal-jugal suture is straight. Scapula - A fragment of a right scapula (MSNT I10148) is preserved (P1.2, fig. 6). The glenoid fossa is moderately concave and oval in shape; its greatest dia- meter is 48 mm and the smaller is 36 mm. Flumerus - The epiphyses of the two humeri are worn and the tubercles. heads and trochleae are not well G. Bianucci & V/. Landini supra- occipita I meolan ridge nuchal crest temporal crest ..--l: fro nto- pa rieta I sutu ra nuchal crest external occip ita I protu be- rance med ia n ridge pa rieta I median valley 5cm internal medial ' p rolu be- ra nce bony falx cerebri temporal cresls supraoccipital Fig. 3 - Skull roof (MSNT I1al4a) oÍ Metaxytherium mediunt ftom the Arenaria di Ponsano Formation. A, dorsal vieu'; B, ven- tral r.iew; C, lateral vien'. preserved (Fig.5; Pl.2, figs. 1,2). The srrong right hu- merus (MSNT I10141) is more than 205 mm long at it exhibits a prominent and elongated deltoid crest. Vell- developed tubercles are separated by a deep and wide bicipital groove. The head apparently is relatively small (but it is worn) and hemispherical. The trochiea is an- essef t!bercle }{ttmer of Mearytherium medium fron the Arenaria di Por.r- sano Formation. A, rìght humerus (MSNT I10111) in medial vieu'; B, the same in anterior vien'; C, left humerus (MSNT I10138) in anterior view. Metaxytherium medium from Miocene of Twscany 569 sq uamosal Fi- ,1 Portion of right squamosal and jugal (MSNT 10068) in lat- eral vìew of Metaxytherium medium from the Arenarìa di Ponsano formation. teroposteriorly flattened and the oleocranon fossa is wide. The left humerus is almost as anreroposteriorly elongated as the right, but its diaphysis is unusually thin and apparently lacks the deltoid cresr. This bone might have suffered a pathological malformation (Fornaciari, pers. com.). Vertebrae - Only vertebral fragments are known. A small portion of an atlas, a corpus of a cervical vertebra, and some incomplete neural arches and transverse proc- esses of thoracic vertebrae are preserved. Ribs - Several fragments and some almost complere ribs are preserved (Pl. 2, figs. 3-5). Comparison. The' lragmentary sirenian remalns from the Arenaria di Ponsano are referable rc Metaxytb- erium medium because: - some well-preserved skeletal elemenrs, such as the skull roof and the humerus, show close resemblances to those of Metaxytherium: - temporal crests of "type E" as in MSNT I1O140, and a very narrow parietal roof as in MSNT 10095, are mosr frequent in M. medium, among the species of this ge- nus; - M. mecJiu;,a is the only known sirenian species in the Late Miocene of the Mediterranean and easrern North Atlantic. Age and stratigraphic occurrence. All specimens were collected in the Arenaria di Ponsano, a Miocene for- mation that consists of sandstone and marls ourcropping in three distinct areas between Volterra and Siena towns (Tuscany, Italy) (Fig. 1). The main outcrop is in the area of Ponsano farm, about 10 km southeastern of Volterra. The sirenian fossils here examined were collected in this Ponsano area where a succession over 500 m thick of sandy sediments representing the upper portion of the formation are exposed (Giannini Ec Tongiorgi 1959 Maz- zanti et al. 1981; Foresi et aL. 1997). These sediments were attributed by Foresi et al. (.1997) to the lr,leogloboquadrina acostaensis Zone. This zone is referable to the early Tortonian (Late Miocene) and to an ase interval between about 10.5 and 8.14 MA. Fìo q 570 G. Bianucci 8t tÀ/. LanJini In the 43 recognized fossiliferous outcrops of this area were collected also fishes (Menesini 1967a), mollusks (Tavani & Tongiorgi 1963), echinoids (Menesini 1967b), cirripeds (Menesini 1963, 1966), foraminifers (Bartolani 1966; Foresi et al. 1,997) and calcareus nannopiancton (Bartolani & Pirini 1969). Discussion and conclusions. Specimens referred to MetaxTtherìum and here de- scribed represent the first Miocene sirenian occurrence from Tuscany and they confirm the wide diffusion of this genus in the Mediterranean area during the Miocene. From a paleoecological point ofview, the occurrence of sirenian remains contributes for a better definition of the environment already indicated by other fossil records. Particularly, the ichthyofauna indicates a subtropi- cal and shallow marine environment with possible estua- rine conditions (Menesini 1967a). The analysis of the foraminifers indicates deposi- tion in the circalitoral-infralitorai zones and. relativelv to the upper part of the succession, a deltaic condition lForesi et al. 19871. These data are confirmed by the sirenians, consider- ing that, as pointed out by Domning (2001) and Domn- ing tc Pervesler (2001), a1l fossil dugongids apparently have been exclusively marine shallow-water and (eccept for hydrodamalines) tropical. Besides, the presence of sirenians indicates that the low sea bottom was at least partially covered by segrass meadows. Infact Domning (2001) hypothesized lor Metax- ytherium spp. a diet based on leaves and rhizomes of smal1 and mid-sized seagrasses in water deeper than 1 meter. Aclenou;ledgemenrs. Special thanks are due to D.P Domning (Laboratory of Paleobiology, Department of Anatomy, Howard Uni- versity, ril/ashington, DC) for very useful suggestions and for a critical reading of a first version of the manuscrìpt. \ùfe also thank A. Varola (Museo dell'Ambiente, Università di Lecce), who collected and restored the specimens here examined, C. Nocchi (Museo di Storia Naturale e del Territorio, Università di Pisa) for her help in the cataloging of the Ponsano fossil collection, and C. Sorbini (Dipartimento di Scienze della Terra, lJniversità di Pìsa), for fruitful discussions and suggestions. The editor (M. Gaetani) and C. Sagne (Muséum National d'Histoire Na- turelle de Paris) made costructive comments on the manuscript. Metaxytherìum nediurn frorn the Arenaria dj Ponsano Formarion. vies.s; 2, skull roof (MSNT I10095) in leteral (a) and dorsal (b) Metaxytherium medium from Miocene of Tuscany 5cm PLATE l l,skull roof (MSNTIl0l+0) ìndorsal (a), ventrel(b) ,letcral (c) andposterior(d) vìen's; 3, portion of right squnosal end jugal (MSNT I10068) in lateral vieu.. 571 572 G. Bianucci &-'V/. Landint PLATE 2 Metaxytheriunt mediun from the Arenarja di I'onsano Form:rion. I, right humeru' (MSNT I10141) in humerus (MSNT 110138) in anteriorvieu,; 3,,1,5, ribs;6, frrqnent r{ rirht sc.rpul.r (MSNT I10148) in fossa (b). mcdial (a) and anterjor (b) views; 2, left lateral vier' (e) end distal vien-of glenoid Aranda-Manteca F. J., Domning D. P E Barnes L. G. (1994) - A new Middie Miocene sirenian of the genus fuletaxy- therium fron'r Baja California: relationships and paleo- biogeograohic in-rolications. In: Berta A. Er Deméré T.A."_'Ò'_-ò_*r'__-'^_'r (eds.) - Contributions in Marine Mammal Paleobiology Honoring Frank C. tMhitmore, Jr. Prctc. San Diego Sctc. Nat. Hrst., 29: 191-204, San Diego. Bartolini C. (1966) - I foraminiferi dell'Arenaria di Ponsano. Palaeont. It., 61: \7 -64, Prsa. Bartolini C. & Pirini C. (1969) - Découverte de nannoplancton calcaire dans Ìe grès de Ponsano, Miocéne Moven, Tosca- ne, Italie. In Brònniam P& Renz H. H. (eds.), Proc. First Int. Conf. Planlet. Microfossils: 81-BB, Geneva. Bianucci G., Landini'M & Varola A. (2003) - Ner.v records of Metaxytherium (Marnmalia: Sirenia) from the late Mio- cene of Cisterna quarry (Apulia, Southern ltaly). Boll. Soc. Paleont. It., 42 (1-2):59-63, Modena. Carone G. (1997) - Metaxytherium medium (Desmarest) 1822 (Dugongidae, Sirenia, Mammalia), delle arenarre torto- niane di Cessaniti (Calabria, kalia). Atti Soc. It. Sci. Nat. Mus. Ciis. St. Nat. Milano, 137:91-fi0, Milano. Cottreau J. (1928) - Le L[etaxytherium cw,uieri du Golfe de la r ^ 7 | t- \I otre. hnn. I'dteontot., I /: J-lu, l'Jrl\. Domning D. P (1988) - Fossil Sirenia of the \il/est Atlantic and Caribbean region. I. Metarytherium floridanwm Hay, 1922. Jour. Veft. Paleortt, 8(4):395-426, Northbrook. Domning D. P (2001) - Sirenians, seagrasses, and Cenozoic ecological change in the Caribbean. Palaectg., Palaeocl., Pal eoecol., | 6b: 27 -5A, A mstcrdem. Don.rning P D & Perr.esler P (2001) - The osteology and re- lationships of Metaxytberium lerahuletzl Deperct, 1895 (Manimalia: Sircnia). Abh. Senck. Natur. Ges.,553: 1- 89, Frankfurt. Domning P D & Thon-ras H. (1982) - Metaxytherium serresii (Mammalia: Sirenia) from the Early Pliocene of Libye and France: a reevaluation of its morpholog,v, phyletic position, and biostratigraphical and paleoecoloeical sig- nificancc. In: Boez N.T., el-Arnauti A., Gaziry A.\{1, de 573 Heinzelin J. & Boaz D. D. (eds.) - Neogene paleorttologt and geologt of Sahabi:205-232, New York. Foresi L. M., Pascucci V & Sandrelli F. (1997) - Larenaria mio- cenica di Ponsano (Toscana, Italia): evoluzione paleoam- bicntale e bio-cronostratigrafica. Boll. Soc. Pal. It., 36: T3-nA, Modena. Gi.rnnini F. & Tongìorgì M. 11059.1 - Stratigrafia neogenic.t to- scana. 1 - Larenaria elveziana di Ponsano (Yolterra). Boll. Soc. Geol. [t.,78(2): 83-100, Roma. Mrzzanti R., Mazzei R., Menesini E. & Salvatorini G. (1981) - Larenaria di Pons:rno: nuove precisazioni sopra l'età. In: IX Cont,egnct della Società Paleontologica ltaliana: 135- 1 60, Pisa. Menesini E. (1963) - Cirripedi miocenici de lle 'Arenarie di Pon- sano" (Volterra, prov. di Pisa). Atti Soc. Tosc. Sci. Nat., Mem., ser. A, 70(1): 15-22, Pisa. Menesini E. (1966) - I balani miocenici delle'Arenarie di Ponsano" (Volterra, prov. di Pisa). Palaeont. I t., 6A: 99 -129, Pisa. Menesini E. (1967a) - I pesci miocenici delle 'Arenarie di Pon- sano". Atti Soc. Tosc. Sci. Nat., Mem., ser. A, 74(1): 1- 22, Pisa. Menesini E. (1967b) - Gli echinidi n-riocenici delle 'Arenarie di Ponsano" (Volterra, provir-rcia di Pisa). Palaeont. (t.,60: 143-167, Ptsa. Moncharmot Zei M. & Moncharmont IJ. (1986) - I1 Meta- xytherium medium (Desmarest) 1822 (Sirenia, Mamma- lia), delle arenarie tortoniane (Miocene sup.) di S. Do- menica di Ricadi (Catanzaro, lr.lit). Mem. Sc. Geol.,39 285-341, Padova. Muizon C. de & Domning D. P (1985) - The first records of fos- sil sirenians in the southeastern Pacific Ocean. Bull. Mus. Natl. Hist. Nar., section C,'[ ser., 7:189-21.3,Paris. Pilleri G., Biosca J. & Via Boada L. (1989) - The Tertiary Si- renia of Catalonia. V of 98 pp. Ostermundigen, Brain Anatomy In.titute. Varnnrala. Tavani G. & Tongiorgi M. (1963) - La fauna miocenica delle 'Arenarie di Ponsano" (Volterra, prov. di Pisa). I parte. Lamellibranchiata. Palaeont. 1r., 5B: 1-43, Pisa. ?I?a REFERENCES