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AMERICAN MUSEUM Novitates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 2904, pp. 1-27, figs. 1-20, 1 table December 30, 1987

The Affinities of Notocetus vanbenedeni, an Early Miocene Platanistoid (Cetacea, Mammalia) from Patagonia, Southern Argentina

CHRISTIAN DE MUIZON' ABSTRACT The study of previously undescribed material the loss of the coracoid process and the acromion of the Early Miocene Odontocete Cetacean No- located on the anterior edge. These three families tocetus vanbenedeni allows a new interpretation of (Platanistidae, Squalodelphidae, and Squalodon- its relationships, and a reevaluation of the taxon tidae) constitute the Platanistoidea. The Squalo- Platanistoidea. The new specimen consists of a dontidae, however, may be poly- or paraphyletic well preserved auditory region (periotic, tympanic, as they are defined by symplesiomorphies only; malleus, stapes, squamosal, and partial occipital) they are not analyzed here and the group is ten- associated with several teeth and some postcranial tatively regarded as monophyletic. The phyloge- elements (scapula, vertebrae, and rib fragments). netic relationships ofthis family will be considered The presence of an articular rim on the periotic elsewhere. The ziphiid affinities ofNotocetus van- and the morphology ofthe tympanic demonstrate benedeni, assumed by some previous workers, are the close relationship of Notocetus with the Plat- rejected. The Ziphiidae could, however, have their anistidae. Notocetus is referable to the family origin in some squalodont-like odontocetes, a Squalodelphidae, which also includes the genera statement which favors a possible polyphyletism Squalodelphis and Phocageneus. This family is the of the Squalodontidae. sister-group ofthe Platanistidae, which consists of Notocetus is an Argentinian genus, but the oc- the genera Platanista, Zarachis, and Pomatodel- currence ofa periotic and a partial tympanic from phis. Platanistidae and Squalodelphidae are re- the Calvert Formation of Maryland extends the garded as the sister-groups of the Squalodontidae distribution of the genus to the Middle Miocene on the basis oftwo synapomorphies ofthe scapula: of North America. INTRODUCTION Notocetus vanbenedeni was first described specimen consisting of a nearly complete under that name by Moreno (1892) on the skull, mandible, some ribs, and vertebrae. basis ofa well preserved skull and associated Both skulls lack the periotics, while a tym- mandible. Later, True (19 10) described a new panic bone is associated with the specimen

' Curator, Institut de Paleontologie, UA 12 CNRS, Museum National d'Histoire Naturelle, 8 rue Buffon 75005, Paris, France. Copyright © American Museum of Natural History 1987 ISSN 0003-0082 / Price $3.70 2 AMERICAN MUSEUM NOVITATES NO. 2904 described by True. The collections of the CNRS (Centre National de la Recherche American Museum of Natural History in- Scientifique) and by the "Fondation de la Vo- clude a specimen (AMNH 29026) here re- cation." Photographs are by D. Serrette and ferred to Notocetus vanbenedeni that consists by the author, ink drawing by F. Pilard, and of a partial right squamosal and occipital, word processing was done by L. Da and E. complete tympanic, periotic and malleus, Molin. several teeth, a scapula, and some incomplete vertebrae and rib fragments. I here describe the most important parts 'of this specimen, ABBREVIATIONS which allows a new interpretation ofthe phy- Institutional logenetic relationships of Notocetus vanbenedeni, a species here classified among the AMNH American Museum of Natural History, Platanistoidea (sensu de Muizon, 1984). New York, USA Ameghino (1894: 43) regarded the genus IGUP Instituto di Geologia del l'Universita di Padova, Italy Notocetus Moreno (1892) as preoccupied by MLP Museo de La Plata, Argentina Notiocetus Ameghino (1891) because the MNHN Museum National d'Histoire Naturelle, names differed by one letter only, and pro- Paris, France posed the new name Diochoticus. The same USNM Smithsonian Institution, United States year, apparently ignorant of Ameghino's National Museum of Natural History, (1894) study, Lydekker (1894: 12) proposed, Washington, D.C., USA for the same reason, the name Argyrodelphis. True (1910: 19), Kellogg (1928), and Colbert (1944) followed Ameghino's designation Abbreviations in illustrations which is two months older than Lydekker's. In fact, it is a recommendation of the Inter- ACR acromion national Code ofZoological Nomenclature to AES anteroexternal sulcus avoid the creation of names which differ by AFI articular facet for incus AFP articular facet for periotic only one letter and which may result in con- AFT articular facet for tympanic fusion to other workers, but once such names AHM articular head of malleus are established they must strictly follow the ALCT anterolateral convexity of tympanic law of priority. It is for this reason that Ca- ALNT anterolateral notch of tympanic brera (1926), Simpson (1945), and Romer APP anterior process of periotic (1969) recognized the genus name Notocetus ARP articular rim of periotic as valid and regarded the name Diochotichus AST anterior spine of tympanic Ameghino (1894), used by True (1910), as a AZS articular zone for squamosal junior synonym of Notocetus. This opinion AZT articular zone for tympanic is followed here. CGL glenoid cavity of the squamosal COP coracoid process CPT conical process of tympanic ACKNOWLEDGMENTS DOCA dorsal opening of cochlear aqueduct DOFA dorsal opening of Fallopian aqueduct Special thanks are due to Drs. M. Novacek DOVA dorsal opening of vestibular aqueduct and R. H. Tedford (American Museum of DTPP dorsal tuberosity of posterior process Natural History), Drs. C. E. Ray and F. C. of periotic Whitmore (U.S. National Museum), and EAM external auditory meatus Professor G. B. Dal Piaz and Dr. L. Altichieri ETF epitubarian fossa (Instituto di Geologia dell'Universita di Pa- EXO exoccipital un- FCM fossa capitis mallei dova) for permission to study specimens FMS fossa for medium sinus der their care. I also thank Dr. L. G. Marshall FPOS fossa for posterior sinus (Geochronology Center at the Institute of FPS falcate process of squamosal Human Origins, Berkeley), R. H. Tedford, FSG foramen singulare M. Novacek, and an anonymous reviewer for HAPP hooklike articular process of periotic helpful comments on the manuscript. Partial IAM internal auditory meatus funding for this research was provided by the IAW internal auditory window 1987 DE MUIZON: NOTOCETUS VANBENEDENI 3

IV involucrum 11) stated that Frenguelli's Patagonian land LFT lateral furrow of tympanic mammals probably come from his bed e and, LLT lateral lobe of tympanic if they are actually from marine beds, this MLT medial lobe of tympanic author sees no MNM manubrium of malleus evidence against the possibil- MPM processus muscularis of malleus ity of an intermediate age between Colhue- MX maxillary Huapi and Santa Cruz. Since no land mam- PA palatine mals have been found in beds right above the PCP pars cochlearis of periotic Patagonian, it may be assumed, pending fur- PEO periotic ther discoveries, that the Patagonian marine PGP postglenoid process mammals have a Colhue-Huapi to Santa Cruz PMP postmeatal process age, i.e., Early Miocene (Marshall et al., 1983, POP paroccipital process 1986; MacFadden et al., 1985). PPP posterior process of periotic PPT posterior process of tympanic DESCRIPTION OF THE SPECIMEN PTT processus tubarius of tympanic PT pterygoid The dentition of Notocetus vanbenedeni RAP relictual articular pit shows slight but obvious heterodonty. The RW round window teeth are all single-rooted, differing from the SPP superior process of periotic posterior teeth ofthe Squalodontidae and the SPS spiny process of squamosal Agorophiidae which are double-rooted (fig. SPT sigmoid process of tympanic 1). The anterior teeth ofN. vanbenedeni have ST stapes a conical and elevated crown which is slightly STF fossa for stapedial' muscle recurved posteriorly and lingually. In shape STMF sternomastoid fossa they resemble typical delphinoid teeth. They TBM tuberculum of malleus UPN notch for unciform process of tympanic show a slight anterior keel, the bases ofwhich UPT unciform process of tympanic sometimes bear one or two tiny cingular cusps. VGT ventral groove of tympanic A posterior keel is hardly discernible and often VOFA ventral opening of Fallopian aqueduct absent. No distinct cingulum can be observed VTP ventral tuberosity of periotic at the base ofthe crown. The enamel is rough- ZPS zygomatic process of squamosal ly rugose, approaching in this respect the morphology observed in Steno and Inia. The LOCALITY AND AGE OF THE SPECIMEN posterior teeth have a low triangular crown; they are approximately triangular in cross The specimen AMNH 29026 was collected section, and the posteriormost teeth are gen- in 1933 by the J. H. Scarritt Expedition, near erally as long as high. Their crown possesses Cerro Castillo opposite Trelew in Patagonia. well marked anterior and posterior keels; the It was discovered in bed g of Simpson's sec- posterior keel bears one, two, or three notable tion of the south wall of the Chubut Valley accessory cusps, the highest sometimes (Simpson, 1935: fig. 1). The sediment is a reaching the apical third of the keel. A chain "thick bedded, pale, yellowish tuff," with Os- of small cingular cusps rise at approximately trea hatcheri, numerous sharks, rays, ceta- half the height of the anterior keel obliquely ceans, and penguins. This bed is commonly joining the centrolingual base of the crown, recorded as Patagonian and according to forming an anterolingual cingulum. This cin- Simpson, is 35 m thick. Below the fossilif- gulum sometimes extends posteriorly to the erous marine Patagonian level is a gray tuff base of the posterior keel. In general aspect, with abundant land mammals (bed e). Ac- the teeth of N. vanbenedeni are very similar cording to Simpson (1935: 1 1): "this fauna to those of Squalodelphis fabianii and Pho- is manifestly of Colhut-Huapi or Santa Cruz cageneus venustus, differing only in the oc- age or intermediate between the two." No currence ofaccessory cusps which seem to be land mammals are recorded by Simpson consistently absent in those two latter species. above the bed g of his section 1. The squamosal of AMNH 29026 is par- Frenguelli (1927) mentioned the occur- tially preserved, and the zygomatic process rence of some land mammal remains in the and articular region of the auditory region Patagonian beds. However, Simpson (1935: are in good condition. 4 AMERICAN MUSEUM NOVITATES NO. 2904

(fig. 2). Its external face shows a well marked fossa for the probable insertion of the m. splenius and part ofthe m. illiocostalis capitis and m. sternomastoideus. Posterior to the postglenoid process is a wide external auditory meatus, the posterior wall of which is formed by a large postmeatal apophysis. This portion of the squamosal is made of spongy and squamous bone, and articulates with the anterolateral edge ofthe paroccipital process; the medial face of the postmeatal process of the squamosal articulates with both the tympanic bulla and periotic. On the lateral side of the process were probably inserted the m. brachiocephalicus and the m. sternomastoideus, the latter apparently being also partially inserted on the apex of the posterior process of the tympanic (see below). A large external auditory meatus and a Fig. 1. Stereophotographs ofteeth ofNotocetus well vanbenedeni (AMNH 29026). (A) Anterior tooth ,developed postmeatal process of the squa- in medial view, (B) posterior tooth in lingual view, mosal are found also in Platanista, Zarachis, (C) the same in occlusal view. Scale x 2.6. Squalodelphis, and Squalodon but they are always much more reduced in the Delphinida The zygomatic process is large and stout, (sensu de Muizon, 1984). and resembles True's specimen more than The medial side ofthe postglenoid process Moreno's in being slightly recurved ventrally shows a fossa for the middle sinus which is

W \Pop Fig. 2. Notocetus vanbenedeni (AMNH 29026). Lateral view of the squamosal and paroccipital process. For abbreviations see text. Scale = 1 cm. 1 987 DE MUIZON: NOTOCETUS VANBENEDENI 5

z ~ ~~~~~~~~~~---

< -> * ~~~~FPOS-

AA"~~~~~~~~~~~ZT8Yj, . . -EA MPOP- -- *_-PE

Fig. 3. Notocetus vanbenedeni (AMNH 29026). Ventromedial view ofthe auditory region. (A) Tym- panic and periotic removed, (B) tympanic removed, periotic in situ. For abbreviations see text. Scale = 1 cm.

much shallower and smaller than in Plata- partially surrounds the periotic and the tym- nista but is similar in shape. The postglenoid panic. Nevertheless, this feature is so rare process is smaller and more acute than in among the odontocetes that it is regarded here Platanista. From its posterior wall slopes a as a synapomorphy of the family Platanisti- dorsomedially oriented crest which reaches dae + Squalodelphidae. Between the spiny the internal base of the postmeatal process process and the subcircular fossa, the squa- and there develops a spiny process which im- mosal is crushed but it is possible to see what bricates with the ventral side of the periotic, was probably a small fossa. In Platanista, between the posterior process and the ventral Zarachis, and Pomatodelphis a similar fossa tuberosity (fig. 3). is seen in the same position, at the base of Dorsal to this spiny process and above the the postmeatal process; it receives the hook- periotic is a deep subcircular fossa which is like articular process which connects the peri- approximately 15 mm long, 9 mm wide, and otic and the squamosal (see below). In No- 8 mm deep in its center. This fossa is also tocetus the process is smaller (articular rim- present in Squalodelphis (IGUP 26378), Po- see below) and was probably lodged in this matodelphis (USNM 187414), Zarachis fossa. Anterior to the periotic and abutting it (USNM 10911), and Platanista but is not is the falcate process of the squamosal. (The found to such an extent in any other odon- termfalcate process is employed here for this tocete (although more reduced in this genus). apophysis of the squamosal following Fraser The function of this structure has not been and Purves [1960]. This term is often used elucidated, although it could represent a sim- to designate the basioccipital crests which will ple extension of the peribulary sinus which be termed here processus alaris or alar pro- 6 AMERICAN MUSEUM NOVITATES NO. 2904

AST.

, ALNT

LLT SPT \\ CPT J~~~~~/ AFP -AZS

-PPT ARP 4<1 C INV D 0 4 2cm

/IAM 1 DOCA / O AW DOWA DOFA VOFA-N T DOWAf~ _STF PPP N

DTPP \ It I T E _ A A E SPPvr FUM F Fig. 4. Notocetus vanbenedeni (AMNH 29026). Right tympanic: (A) lateral view, (B) ventral view, (C) medial view. Right periotic: (D) lateral view, (E) dorsal view, (F) ventral view. For abbreviations see text. cess.) It is slightly damaged but it is possible On the anterior border of the falcate pro- to note that, as in Zarachis, it was much cess are some fragments ofthe lateral lamina broader than that of Platanista. ofthe pterygoid which most probably formed 1 987 DE MUIZON: NOTOCETUS VANBENEDENI 7 a continuous bridge from the squamosal to the palatine. This condition is clearly seen on the skull described by True (1910) but also exists in Squalodelphis, in the Squalodonti- A dae, and in the Platanistidae. The periotic and the tympanic of AMNH 29026 are exceptionally well preserved (fig. 4). The terminology employed for the de- B scription of these bones is that used by de Muizon (1984) which partially follows Ka- suya (1973) and Fordyce (1983). -C_C The periotic ofNotocetus vanbenedeni (fig. Fig. 5. Notocetus vanbenedeni (AMNH 29026). 5) is mainly characterized by the large size of Stereophotographs of right periotic: (A) dorsal its anterior and posterior processes. The an- view, (B) ventral view, (C) lateral view. Scale terior process is much longer and more slen- xO.50. der than in Platanista although it has the same robust aspect in ventral view. In its length, it could approach the condition found in some sembling in this respect that of the rhabdo- rhabdosteids but it is always thicker and more steids and differing from that ofthe platanis- swollen, mainly in ventral view. This side of tids. the process shows a regularly curved lateral The posterior process ofthe periotic is well edge from the fossa capitis mallei to the apex. developed; posterolateral to the dorsal open- There is no distinct ventral rim as can be seen ing of the vestibular aqueduct it bears a sa- in the Delphinida, but the ventral tuberosity, lient dorsal tuberosity which is separated from whose medial side bears the fossa capitis mal- the articular part of the process by an abrupt lei, is more pronounced than in Platanista narrowing. This condition is clearly visible and Squalodon, but it is similar to that in in posterolateral view. A slightly curved crest Zarachis and Pomatodelphis. The epitu- joins the top of the tuberosity and the apex barian fossa which receives the processus tu- of the posterior process. From the anterolat- barius of the tympanic is long and deep, and eral border ofthe tuberosity, a short rounded covers half the length of the ventral side of crest (3.5 mm wide and 8 mm long), which the anterior process. It is much longer than is termed the articular rim, is directed an- in any Platanistidae and Squalodontidae, a teroventrally into the deep notch which sep- feature even more emphasized in USNM arates the ventral tuberosity and the articular 206286 (see below); however, it approaches facet ofthe tympanic. This notch receives the the condition found in some Rhabdosteidae. spiny process of the squamosal which passes Posterior to the epitubarian fossa is a deep ventrally to the articular rim. The latter is transverse notch which received the unci- lodged in the small fossa of the squamosal, form process of the tympanic. This notch is mentioned above, dorsal to the postmeatal less emphasized than in Platanista but, con- process. sidering the variation shown by this struc- An almost identical condition is found in ture, it is close in size to that of Zarachis, Phocageneus venustus and in Squalodelphis Pomatodelphis, and Squalodon. The lateral fabianii where the articular rim is empha- side of the anterior process presents a well sized as a small apophysis. However, the de- marked anterolateral sulcus; it is V-shaped velopment of this structure in Notocetus and opens anteriorly. Its ventral part is nar- shows some variation; as in P. venustus row and deep, whereas its dorsal part is wide (USNM 21039) the right periotic bears a small and shallow. Such a groove is generally well apophysis similar to that ofS. fabianii, while marked in fossil platanistids like Zarachis the left periotic only has an articular rim close and Pomatodelphis and in some rhabdo- to that of N. vanbenedeni. The configuration steids; it is hardly visible in squalodonts and found in the Squalodelphidae is also very strongly attenuated by the hyperostosis ofthe similar to that found in some Platanistidae, anterior process in Platanista. The apex of although it is always more specialized in this the anterior process is pointed and sharp re- family. In Pomatodelphis and Zarachis the 8 AMERICAN MUSEUM NOVITATES NO. 2904

The superior process is like that in other platanistids, being more excavated than salient. In fact, as I have already expressed (de Muizon, 1984), the term is not very appro- Fig. 6. Zarachis cf.flagellator (USNM 13768). priate for this structure, as it is more often a Stereophotograph of the right periotic in lateral flat zone than a process and its posterior ex- view, showing joint occurrence of the hooklike tremity is very rarely distinguishable from articular process and the articular peg. Scale x 0.53. the posterior process. In AMNH 29026 and in some Platanistidae, there is a distinct slit posterolateral to the dorsal opening of the articular rim has developed laterally and pos- vestibular aqueduct which separates both teriorly into a hooklike articular apophysis processes. However, the presence of this slit which enters a corresponding fossa in the is variable within platanistids. squamosal at the base ofthe postmeatal pro- The pars cochlearis has a square-shaped cess. The periotic and the squamosal are in- outline as in Phocageneus and Squalodelphis. terlocked in such a way that it is impossible This condition is found sometimes in Za- to separate them without breaking either the rachis and Pomatodelphis, although in these articular process or the fossa. In Platanista two genera this feature is never as obvious the condition is even more specialized as the as in Notocetus vanbenedeni. The cochlea is tuberosity of the posterior process is much not square-shaped in Platanista nor in any higher, the articular part much reduced, and other Neogene odontocetes. The cochlea of the groove between it and the hooklike ar- Notocetus vanbenedeni shows an anterodor- ticular process is much narrower. The peri- sal projection ofthe anteromediodorsal angle otic ofPlatanista is hence even more difficult of the pars cochlearis. The Notocetus condi- to remove from the skull. This condition is tion is common, and sometimes much more highly derived and must be regarded as a emphasized, in the Platanistidae, some synapomorphy of Notocetus, Phocageneus, Squalodontidae, and some Rhabdosteidae. It Squalodelphis, and the Platanistidae. The ar- is probably a plesiomorphic character which ticular process must not be confused with a recalls the primitive flat condition ofthe pars small articular peg which is found at the same cochlearis and an ancestral hypothetical con- position in some rhabdosteids. This peg is a tact with the alisphenoid. However, it is note- relict of an ancestral articulation between worthy that this feature can be accentuated periotic and squamosal which may reappear in some groups (i.e., ziphiids, platanistids). sporadically, as an indication of individual On the dorsal side of the pars cochlearis, variation. It has a typical laminated structure the internal auditory window (comprising the which strongly differs from the pachyostotic internal auditory meatus + foramen singu- bone of the articular process. The fact that lare + dorsal aperture ofFallopian aqueduct; both articular peg and hooklike articular pro- see de Muizon, 1984) is almost circular as in cess are sometimes found together in Za- Platanista while it is generally pyriform in rachis supports this observation (fig. 6). the other platanistids. The foramen singulare The articular facet for the posterior process is small and almost assimilated to the dorsal of the tympanic is smooth, gently concave, aperture of Fallopian aqueduct. In this re- and longer than wide; it is similar in shape spect Notocetus vanbenedeni resembles Plat- to that ofZarachis, Pomatodelphis, and Pho- anista and Phocageneus but differs from Za- cageneus but much wider than that of Plata- rachis and Pomatodelphis. nista. The dorsal aperture of the cochlear aque- The anterior extremity ofthe articular facet duct is very close to the edge of the internal is slightly damaged. However, it is possible auditory meatus; it is large with very thin to note the absence of a distinct fossa crus edges and faces almost dorsally. In this re- breve incudis. A similar condition also exists spect, it differs from the condition found in in Phocageneus and Platanista, but a shallow most platanistids, squalodontids, and rhab- fossa is generally found in Zarachis, Poma- dosteids, where it is generally small, and has todelphis, and in squalodonts. thick edges. Among the platanistoids it is al- 1 987 DE MUIZON: NOTOCETUS VANBENEDENI 9 most identical to that of Phocageneus and Squalodelphis. However, in this latter genus the foramen is slightly smaller and its edges are not as thin as in the two other genera. The dorsal aperture of vestibular aqueduct is similar to that found in Platanistidae. On the ventral side of the pars cochlearis just lateral to the fossa capitis mallei is a longitudinal crest. This crest is found sometimes in Zarachis and some squalodonts, but it is always less developed in these taxa. The oval window is located in the bottom of a distinct pit posterior to which is found a large fossa for the m. stapedius. This fossa is clearly sep- arable from the round window fossa by a distinct transverse crest, a condition very well marked in Phocageneus and squalodonts; the crest is sometimes present, but less developed, in some rhabdosteids. The condition Fig. 7. Notocetus vanbenedeni (AMNH 29026). is never present in Platanistidae and could Stereophotographs of right tympanic: (A) ventral represent a plesiomorphic feature. view, (B) lateral view, (C) medial view. Scale The tympanic (fig. 7) is the bone which x0.50. allows reference of AMNH 29026 to Noto- cetus vanbenedeni as it is almost identical to that figured by True (1910) and associated The sigmoid process is roughly square- with the skull AMNH 9485. shaped anteriorly and is oriented more pos- The outer lip of the tympanic is very high, terodorsally than dorsally, as it is in Plata- as in Phocageneus, Squalodelphis, and to a nista. The conical process is moderately larger extent the Platanistidae. This condi- developed as in Zarachis and Pomatodelphis tion seems unique among Miocene odonto- but it is smaller than in Platanista. Its pos- cetes, but could not be observed in the terolateral side presents a small crest which Squalodontidae because of the lack of com- reaches the base of the lateral pedicle of the plete tympanic available for this study. The posterior process. The latter is posterolater- outer lip of the tympanic of Notocetus van- ally oriented and bears the articular facet with benedeni is very convex and inflated, partic- the periotic. Posterior to the facet is a zone ularly on its anterior extremity posterolateral of laminate bone which articulates with the to the anterior spine; this anterolateral con- postmeatal process of the squamosal in such vexity is, in fact, an extension of the proces- a way that the apex of the process extends sus tubarius on the dorsal edge of the lateral slightly lateroventrally, and the process prob- lip. It is separated from the anterior spine by ably received some fibers of the m. sterno- a smooth notch. The same condition is found mastoideus and/or the m. mastohumeralis. in Zarachis, Phocageneus, and Squalodel- On the anterolateral edge of the posterior phis. The processus tubarius is much less de- process is a deep groove which receives the veloped in Platanista but more pronounced ventral crest ofthe spiny process ofthe squa- in Pomatodelphis (USNM 187414 and mosal. The posterior process ofthe tympanic MNHN FS 2342). Posteriorly, on the lateral of Notocetus vanbenedeni has therefore a lip of the tympanic, is a very fine slit which double articulation with the periotic and the seems to be homologous to the deep lateral squamosal. This condition has been dem- furrow found in Zarachis, Pomatodelphis, and onstrated to be plesiomorphic (de Muizon, Platanista. The conditions in Phocageneus 1984) and the loss of the tympanic-squa- and Squalodelphis are apparently interme- mosal articulation has been regarded as a syn- diate between that of the Platanistidae and apomorphy of the Rhabdostoidea + Inioi- that of Notocetus vanbenedeni. dea + Delphinoidea (de Muizon, 1984: 68). 10 AMERICAN MUSEUM NOVITATES NO. 2904

the involucrum is stout, straight, and conical at its anterior extremity. It differs from the more dorsoventrally inflated involucrum of Pomatodelphis and Zarachis and from that of Platanista whose height is reduced mark- edly at its anterior extremity. The involucrum of Phocageneus seems to be closer to that of Zarachis than to that of Notocetus, but in Prosqualodon the involucrum is fairly similar to that of N. vanbenedeni in being little inflated dorsoventrally. The ventral side of the tympanic shows a distinct longitudinal groove continuous from the anterior spine to the posterior notch, which separates the lateral and medial lobes. This groove also reaches the anterior spine in Phocageneus and Squalodelphis but it stops anterior to it in Squalodon, Prosqualodon, C Zarachis, Platanista, and Pomatodelphis. The Fig. 8. Stereophotographs of posteromedial ventral groove of Notocetus is not filled with view of the malleus of (A) Notocetus vanbenedeni a spine of spongy bone as is found in Plata- (AMNH 29026), (B) Phocageneus venustus (USNM nista and Pomatodelphis. There is no spine 21039), (C) Pomatodelphis cf. inaequalis (USNM in Zarachis or in Phocageneus, but the bot- 187414). Scale x2.6. tom ofthe groove exposes some spongy bone as in some rhabdosteids. A similar condition It is also probable that the posteroapical angle is observed in Notocetus vanbenedeni and of the process had a contact with the paroc- Squalodelphis fabianii. Both lobes have the cipital process. same length posteriorly and their posterior The posterior process of AMNH 29026 is extremities have approximately the same shorter than that of AMNH 9485; they both thickness. The Notocetus condition is also strongly resemble that of Phocageneus al- found in Phocageneus, Squalodelphis, and though the former is slightly shorter. The squalodonts. condition in Platanista is different because In Platanistidae and Rhabdosteidae the the lateral groove is absent, the articulation medial lobe is generally shorter and thinner with the squamosal has moved anterolater- than the lateral one. The anterolateral con- ally, and the process is not so elongate as in vexity and notch are very clearly seen in that N. vanbenedeni. The posterior process of view and show strong similarities with Pho- Zarachis is unknown, but in Pomatodelphis cageneus and Squalodelphis, as mentioned (USNM 187414) and squalodonts, the con- above. The anterior spine is well developed dition is similar to that of Notocetus. The as in the Platanistidae and the other Squalo- posterior process is attached to the bulla by delphidae. two pedicles and a transversely elongate, el- The malleus (figs. 8, 9) is well preserved liptical foramen is seen in posterior view of and its similarity to that of Platanistidae was the tympanic. In this view, the ventral side mentioned by de Muizon (1985: fig. 1). In being horizontal, the involucrum is strongly that paper (de Muizon, 1985), the specimen protruding medially, as in Phocageneus, USNM 187414 was erroneously referred to Prosqualodon, and (to a lesser extent) in the Zarachis, but, on the basis of the skull and Platanistidae. (Because ofthe transverse pos- the tympanic, it must be assigned to Pomato- terior compression of the tympanic in plata- delphis. The malleus of Notocetus shows a nistids, the involucrum is less prominent.) strong development of the tuberculum rela- A different condition is found in the Rhab- tive to that-in Pomatodelphis. In this respect, dosteidae and in all groups of modem Odon- it resembles Phocageneus and Squalodelphis, tocete. On the medial side of the tympanic, but also the delphinid condition, and clearly 1 987 DE MUIZON: NOTOCETUS VANBENEDENI I 1

A @ - __-AHM '

Fig. 9. Posteromedial view of the malleus of (A) Notocetus vanbenedeni (AMNH 29026), (B) Pomatodelphis cf. inaequalis (USNM 187414). For abbreviations see text. Scale x 3.4. Fig. 10. Notocetus vanbenedeni (AMNH 29026). Lateral view ofthe scapula. Scale = 2 cm. differs from rhabdosteids. The posteromedial aspect ofthe malleus is the most relevant and served in situ on the periotic. Although this will be described with its mediolateral axis latter bone is incomplete, it is noteworthy in vertical position. The articular head bears that the stapes does not have a stapedial fo- the articular facets for articulation of the in- ramen. The Squalodontidae, Platanistidae, cus; they are similar to those of Pomatodel- and Phocageneus also lack this foramen, but phis. The tuberculum bears the manubrium it is present in rhabdosteids and delphinoids. and the processus muscularis. The manu- The occipital has a well developed paroc- brium in Pomatodelphis is hook-shaped and cipital process which shows on its anterior presents on its ventral side a groove for the surface a large fossa for the posterior sinus insertion of the tympanic ligament. In No- (fig. 3). The fossa is more pronounced near tocetus the manubrium is smaller, much less the dorsal end of the process where it forms recurved, more expanded apically, and the a deep hollow. The depth of the fossa, how- groove is longer than in Pomatodelphis. The ever, is not related to the size ofthe posterior condition in Phocageneus and Squalodelphis sinus. In Stenella and Tursiops, where the is closer to that in Notocetus than to that in fossa is very shallow, the sinus is large. Pomatodelphis. The apical extension of the The processus alaris of the basioccipital is manubrium is not found in the Platanistidae thick, a primitive condition found in Plata- and could be a synapomorphy ofthe Squalo- nistidae and Squalodontidae and also in Pon- delphidae. toporiidae and Rhabdostoidea. The base of On the dorsal side of the tuberculum is a the lateral face of the alisphenoid shows a distinct pit for the insertion ofthe tendon for well developed carotid foramen. the tensor tympani. The processus muscu- Among the postcranial elements preserved laris which bears that insertion is lower than in AMNH 29026, the most significant bone the apex of the manubrium, resembling is the scapula (fig. 10). The specimen is not therefore the primitive condition found in very complete but shows two essential fea- mysticetes and platanistids. As has been stat- tures of phylogenetic significance. First, the ed (de Muizon, 1985), the Delphinida are coracoid process, which is always long in defined, in part, by an apical increase in size odontocetes and in such primitive groups as of the processus muscularis and by a reduc- archaeocetes, is absent in Notocetus. As ob- tion of the manubrium which, in postero- served by de Muizon (1984), it is also absent medial view, is lower than the processus mus- in Platanista and Squalodontidae and it is cularis. In this respect, Notocetus vanbenedeni always present in the Delphinida (see de Mui- resembles Pomatodelphis, Phocageneus, and zon, 1984), Rhabdostoidea, Ziphioidea, and Squalodelphis and -clearly differs from the Physeteroidea. (In Zarachis, Pomatodelphis, Delphinida. Phocageneus, and Squalodelphis, the scapula The incus is not preserved in AMNH 29026 has not yet been found.) Second, the acro- and only the basal part of the stapes is pre- mion is located exactly on the anterior edge 12 AMERICAN MUSEUM NOVITATES NO. 2904

TABLE 1 Measurements of Squamosal, Periotic, Tympanic, and Malleus of Notocetus vanbenedeni (AMNH 29026) in mm Length of zygomatic process of squamosal from the bottom of the external auditory meatus to apex 70.2 Length of periotic 43.6 Maximum width of periotic 24.6 Maximum length of the pars cochlearis 15.3 Maximum length of the ventral side of tympanic 50.0 Maximum width of the ventral side of tympanic 32.2 Maximum length of tympanic (with posterior process) 52.3 Height of the posteromedial face of malleus 7.1 Width of the posteromedial face of malleus 4.6

ofthe scapula, probably as a result ofthe total gonian Fm." of the Trelew region in Chubut absence of the supraspinous fossa. This con- Province (Argentina). dition is also found in Platanista and in all The collection of the U.S. National Mu- the Squalodontidae (where the scapula is pre- seum of the Smithsonian Institution in served enough to enable the observation). All Washington contains a periotic which, if not the other odontocetes and all the archaeo- associated with a tympanic, could be refer- cetes have a supraspinous fossa, although it able to Notocetus vanbenedeni (fig. 11). The is small in the most specialized forms. These specimen (USNM 206286) comes from the two characters, which could be functionally Middle Miocene age Calvert Formation of related, are so unique among cetaceans that Maryland. It presents a long and laterally in- they can be considered as good synapomor- flated anterior process with an acute apex, a phies of Platanistidae, Squalodelphidae, and square-shaped cochlea with a wide, thin- Squalodontidae (de Muizon, 1984). edged dorsal aperture of the cochlear aqueduct, a deep fossa for the stapedial muscle, an articular rim born from the dorsal tuber- OTHER MATERIAL REFERRED osity of the posterior process, and a narrow TO NOTOCETUS crest joining the tuberosity to the apex of the The collection of the La Plata Museum process. All these features are found in No- (Argentina) contains several specimens that tocetus vanbenedeni. USNM 206826 differs are referable to Notocetus vanbenedeni. from Phocageneus essentially by the length 1. MLP 5-5 is the holotype. and the thickness of its anterior process. 2. MLP 5-10 is a partial skull with asso- However, USNM 206286 also differs from ciated mandible, designated in the collection Notocetus vanbenedeni in its longer and less as paratype. Most of the posterior part of the swollen anterior process, its less developed skull is missing and the skull mainly consists ventral tuberosity, its smaller articular facet of a rostrum with the right supraorbital re- for the tympanic, and its more salient artic- gion and anterior part ofthe pterygoid region. ular rim. Nevertheless, considering the scar- Most of the teeth are well preserved. city of the specimens referred to Notocetus, 3. MLP 76-X-2-5 is a right periotic, whose these features could represent individual posterior process has lost its articular region. variation. The characteristic shape of the anterior pro- Associated with the USNM periotic is a cess of the lateral side of the posterior pro- partial tympanic in which are preserved the cess, the square-shaped cochlea, and the large, involucrum and the median part of the ven- thin-edged dorsal opening of the cochlear tral groove. In ventral view, the medial lobe aqueduct, cast little doubt about its identity. is slightly different from that of Notocetus 4. MLP 76-IX-2-11 and 76-IX-2-12 are vanbenedeni in being narrower and more tympanics that are also referable to N. van- concave in its median part (it is almost straight benedeni. in both specimens ofNotocetus vanbenedeni). All these specimens come from the "Pata- In True's specimen (AMNH 9485), however, 1987 DE MUIZON: NOTOCETUS VANBENEDENI 13 there is a very weak medial concavity and 1. the median part of the medial lobe is nar- V. rower than in AMNH 29026. In medial view, A the anterior part of the involucrum is rela- tively more swollen than in N. vanbenedeni, .4 .... and shows a distinct convexity in its posterior part. In these features, the condition ofTrue's B specimen is intermediate between AMNH '71,., e C,- 29026 and USNM 206286 although closer to t-:- the other Patagonian specimen (AMNH 29026). Despite the important similarities C existing between the periotics of the Argen- Fig. 11. Notocetus sp. (USNM 206286). Ste- tinian and North American specimens, the reophotographs of right periotic: (A) dorsal view, latter should be referred to another species (B) ventral view, (C) lateral view. Scale x 0.50. ofthe genus Notocetus, a conclusion that takes into account the differences existing between the anterior processes ofthe periotics ofboth Family Squalodontidae (among others, species. tSqualodon, tProsqualodon, tNeosqua- lodon, tPhoeberodon) DISCUSSION The classification adopted here is very sim- PLATANISTOID CLASSIFICATION ilar except for some minor changes (see fig. Traditionally (Simpson, 1945; Bourdelle 12). and Grasse, 1955), the taxon Platanistoidea Areodelphis, regarded (de Muizon, 1984) was defined to include the four genera of liv- as a possible Platanistidae, is known only by ing river dolphins and related fossil forms. a rostrum and a referred vertebral column. Hershkovitz (1966) used the term Susuidae As no auditory region of this form can be (=Platanistidae) but assigned to it the same associated to the type specimen it must be set of taxa as did Simpson. Rice (1968) also considered as incertae sedis. followed Simpson (1945). Zhou (1982) in- Phocageneus is not a Platanistidae but a cluded each of the four living genera in a Squalodelphidae because of its auditory re- separate family: Pontoporiidae, Iniidae, gion morphology. Lipotidae, and Platanistidae. Recently, Barnes In the Squalodontidae should also be in- et al. (1985) used the same classification, but cluded the following genera: Eosqualodon, included the family Acrodelphidae, a fossil Australosqualodon, Kelloggia, Microcetus, group they regarded as including Schizodel- Parasqualodon, and Tangaroasaurus. How- phis, Pomatodelphis, and probably Zarachis. ever, the abundance of incertae sedis taxa in de Muizon (1984, 1985) suggested a new in- the classification given by Whitmore and terpretation ofthe phylogeny ofthe river dol- Sanders (1977: 305) is an indication of the phins as a polyphyletic assemblage. The fam- crucial need for revision of the squalodonts ily Platanistidae was recognized to include and other related primitive cetaceans. Such only the living genus Platanista while the three a revision may possibly result in elevation of other living genera were related to the Del- this family to the rank of superfamily. phinoidea and, with that superfamily, were Therefore, the classification proposed here included in the infraorder Delphinida (de is as follow: Muizon, 1984). The following classification Superfamily Platanistoidea was proposed: Family Platanistidae (Platanista, tZara- Superfamily Platanistoidea chis, tPomatodelphis) Family Platanistidae (Platanista, tZara- Family Squalodelphidae (tNotocetus, chis, tPomatodelphis, tPhocageneus, tSqualodelphis, tPhocageneus, possibly tAreodelphis) t"Champsodelphis" ["C." tetragorhi- Family Squalodelphidae (tSqualodelphis, nus]) tNotocetus) Family Squalodontidae (tAustralosqualo- 14 AMERICAN MUSEUM NOVITATES NO. 2904

PLATANISTIDAE SQUALODELPHIDAE don, tEosqualodon, tKelloggia, tMicro- cetus, tNeosqualodon, tParasqualodon, cn cn 0 tPhoeberodon, tProsqualodon, tSqualo-

I w -J cn z don, tSulakocetus (?), tTangarosaurus) Z w D 0 Ce) a W 0 Z I O o O w 0 C < IJ -J PLATANISTOID PHYLOGENY (FIG. 12) t) ~< O o D J < 0 I a 0 a a. N a. a. cn z cl) Platanistoidea The Platanistoidea bear two important shared derived characters on the scapula. As discussed above, the platanistoid scapula has lost its coracoid process while it is very large in all other odontocetes and in archaeocetes (fig. 13). Moreover, the acromion is always situated on the anterior edge of the scapula and there is no supraspinous fossa, while this fossa is always present in the other odontocetes and in the archaeocetes. As stated in the preceding description, these two features are probably related, but no satisfactory func- tional explanation was found. Hence, they are

12. apical extension ofthe manubrium ofthe malleus; 13. very strong development of dorsal transverse process of the atlas and extreme reduction of Fig. 12. Assumed phylogenetic relationships the ventral process; of the Platanistoidea: 14. loss of accessory cusps of the posterior teeth; 1. acromion located on the anterior edge of the 15. anterior spine longer than in Notocetus; scapula and loss of supraspinous fossa; 16. lateral furrow of the tympanic better marked 2. loss of the coracoid process of the scapula; than in Notocetus; 3. the phylogeny of the squalodonts is not con- 17. occurrence of a small longitudinal elevation sidered here and the group is tentatively re- in the ventral groove of the tympanic lacking garded as monophyletic, although Sulakoce- in Notocetus; tus should perhaps be excluded from the fam- 18. articular rim more developed than in Noto- ily (see text); cetus; 4. development of a supplementary articular 19. development ofvery high maxillary crests on mechanism with the squamosal on the lateral the supraorbital region of the skull; edge of the periotic (articular rim); 20. dorsolateral migration of the palatine bones, 5. development ofa long, narrow, sharp anterior which are separated from each other; spine on the tympanic with salient anterolat- 21. reduction in length and transverse thickness eral convexity separated from the spine by of the medial lobe of the tympanic; prominent notch; 22. greater elevation ofthe lateral wall ofthe tym- 6. loss of double rootness; panic; 7. tendency toward thickening of the supraor- 23. transformation of the articular rim of the bital process; Squalodelphidae into a hooklike articular pro- 8. deep subcircular fossa dorsal to the spiny process; cess of the squamosal; 24. shortening and transverse thickening of the 9. square-shaped pars cochlearis of the periotic; anterior process of the periotic; 10. large, thin-edged dorsal opening of the coch- 25. frontal associated with the maxillary to form lear aqueduct, which faces dorsally; a supracranial frontomaxillary crest; 11. ventral groove of the tympanic affecting the 26. involucrum more elevated than in Platanista; whole length of the bone including the ante- 27. dorsoventral thickening of the anterior pro- rior spine; cess of the periotic. 1987 DE MUIZON: NOTOCETUS VANBENEDENI 15

ACR

-+1. . w4,

,Zik- ,/ACR

. t- It, -ACR

Fig. 13. Scapulae ofPlatanistoidea in medial view. (A) Prosqualodon (AMNH 29022), (B) Squalodon (USNM 22902), (C) Notocetus (AMNH 29060), (D) Platanista (MNHN 1870-79). For abbreviations see text. Not to scale. tentatively maintained as independent syn- by Mchedlize (1976: pl. XIII) seems to be apomorphies ofthe Platanistoidea. However, fairly primitive, but it apparently shows a it is noteworthy that the scapula of Sulako- maxilla contacting the occipital, a condition cetus figured by Mchedlize (1984: pl. XVI) which makes it different from the primitive seems to have a well developed coracoid pro- Agorophius or Xenorophus or even from the cess and that author mentions a "coracoid less primitive Patriocetus (a genus related to process narrow but apparently long" (Mched- the Squalodontidae by Rothausen, 1968), lize, 1984: 43). Nevertheless, the acromion where the bones are always separated. Su- seems to show the platanistoid condition de- lakocetus should perhaps be regarded as a scribed above. Therefore, it is possible that primitive squalodont-like platanistoid, but it Sulakocetus could represent the sister-group is clear that a more detailed analysis of the of all other Platanistoidea which can then be skull and especially the auditory region ofthis defined only by the loss of the coracoid pro- form is necessary for identification ofits phy- cess. The superfamily Platanistoidea (incl. logenetic position. The synapomorphies of Sulakocetus) would thus be defined by the the Platanistoidea must be assumed to exist anterior position ofthe acromion and the loss in Squalodelphis, Phocageneus, Zarachis, and of the supraspinous fossa. Pomatodelphis as the scapulae ofthese genera The scapula of Sulakocetus is very poorly are unknown. However, these taxa bear other preserved and a better specimen is needed to synapomorphies which relate them to the be certain of its condition. The skull figured Platanistidae and Squalodelphidae and it is 16 AMERICAN MUSEUM NOVITATES NO. 2904

plausible that they also possessed the plata- cess demonstrates the novel formation ofthe nistoid synapomorphies of the scapulae. latter and, therefore, its apomorphic status. Consequently, the presence of an articular Squalodontidae process on the lateral side of the periotic, even incipiently developed as is the articular In the following discussion the Squalo- rim ofsome Squalodelphidae, is regarded here dontidae are regarded as a possible mono- as a synapomorphy of the Platanistidae and phyletic group, as it is not the purpose ofthis the Squalodelphidae (fig. 14). All the genera paper to reanalyze this family. However, one ofboth families show a large subcircular fos- must be aware that, until now, the Squalo- sa. This structure is unknown in all the other dontidae are "defined" only by symplesio- odontocetes, and is also regarded here as a morphies, such as heterodont dentition, dou- synapomorphy of the Squalodelphidae + ble-rooted posterior teeth, low vertex, and Platanistidae (see above). The fossa is only narrow occipital shield. Consequently, this inferred to be present in Phocageneus since group may be demonstrated to be nonmon- the skull ofthis form is unknown. Moreover, ophyletic. Furthermore, few squalodonts are the supraorbital process of both families is known by complete skulls with associated clearly more developed than in the other periotics, tympanics, and auditory ossicles. odontocetes. In the Squalodelphidae, the elements regarded here as important phylo- process is strongly thickened, this character genetically. The type skull of Squalodon being more pronounced in Squalodelphis than (=Rhizoprion) bariense (Jourdan, 186 1), in Notocetus. In Phocageneus, however, it is whose ventral side is still embedded in ma- only assumed to be present since the skull of trix, and which still retains these bones in this genus is unknown. In the Platanistidae, good condition, is being reprepared and re- the thickening turns into a real supraorbitory studied by the author and will perhaps shed crest (see below). Both families are also de- more light on the problem ofsqualodont phy- fined, relative to squalodonts, by the lack of logeny. double-rootness and by the acquisition of a long, narrow, and sharp anterior spine of the Squalodelphidae + Platanistidae tympanic with an anterolateral notch and The Platanistoidea were defined (de Mui- convexity. These are sometimes less empha- zon, 1984: 68) by the presence of a hooklike sized in Platanista but, as noted in the de- articular process on the lateral side of the scription, they are always strongly marked in periotic between the ventral tuberosity and Pomatodelphis. This condition of the tym- the articular part of the posterior process. As panic in Squalodelphidae and Platanistidae noted above and elsewhere (de Muizon, is either absent or very little developed in 1984), this condition is very clear in the Plat- primitive odontocetes like squalodonts, ago- anistidae; it is present but less developed rophiids (undescribed material, USNM), and (forming only an articular rim) in the Squalo- archaeocetes. The development of an ante- delphidae. I have stated (de Muizon, 1984: rior spine to the tympanic also occurs through 67) that the condition of the Squalodontidae parallel evolution in some rhabdosteids, some shows some variation and is not very obvious delphinids (Globicephala), and in Lipotes, but in Prosqualodon. In fact, as noted above, the in these forms the anterior spine is more con- condition of Squalodontidae seems to be a ical, wider, and less acute. holdover of an ancestral articulation of the periotic with the spiny process of the squamosal, where spongy and laminated bone that Squalodelphidae characterizes cranial articulations is present. Until now, the periotic and malleus of The squalodont condition may be found oc- Squalodelphis fabianii were unknown since casionally in rhabdosteids and monodontids the tympanic is in situ in the holotype and as the retention ofa plesiomorphic character. does not allow any observation ofthese bones The fact that it may be observed in some (Dal Piaz, 1916b: pl. 3). The skull portion Platanistidae like Zarachis between the pos- with attached periotic (IGUP 26377) illus- terior process and the hooklike articular pro- trated by Pilleri (1985: pl. 29) and referred 1987 DE MUIZON: NOTOCETUS VANBENEDENI 17

Ix .,7 ., --- .

ARP/B A ARP B ARP C ,HAPP

, . / HAPP

I -I i HAPP-_

janow D E F Fig. 14. Periotics of Platanistoidea in lateral view. (A) Squalodon (cast of USNM 10484), (B) No- tocetus (AMNH 29060), (C) Phocageneus (cast of USMN 21039), (D) Zarachis (USNM 13768), (E) Pomatodelphis (USNM 187414), (F) Platanista (MNHN 1870-79). For abbreviations see text. Scale x 0.46. to Squalodelphis does not belong to this ge- brium that is lacking in Pomatodelphis and nus. This skull and its periotic (which I have Platanista (figs. 8, 9, and 16). prepared) are probably those ofa rhabdosteid The tympanics of the three Squalodelphi- or a primitive ziphid, but definitely not that dae are very similar; they show the anterior of a squalodelphid. The specimen IGUP spine and the anterolateral notch and con- 26378 illustrated by Pilleri (1985: pl. 30) has vexity that are absent or little developed in a tympanic which is identical to that of the Squalodontidae. The tympanics also have holotype of S. fabianii; furthermore, its skull ventral lobes equally long and equally thick base perfectly matches that of S. fabianii to posteriorly as in squalodonts, which contrast which it may reasonably be referred. I had with Platanistidae where there is always a the opportunity to prepare the periotic and reduced medial lobe. These features are sym- the malleus of IGUP 26377 (fig. 15 and 16), plesiomorphies only (fig. 17). Nevertheless, and the references made to the periotic and the tympanics of the three known genera of malleus of Squalodelphis in the above de- Squalodelphidae show the same ventral scription are based on this specimen. groove that is continuous up to the anterior As stated above, the periotic of Squalo- delphis shows the typical synapomorphy of the Platanistidae + Squalodelphidae. The synapomorphies of the Squalodelphidae are mainly based upon characters ofthe auditory region since other areas of the skull of Pho- A cageneus are unknown. The three genera included in the family share two characters of the periotic which seem to be fairly uniform among the odontocetes: the typical square- | ~~~~~~~~B shaped pars cochlearis and the large, thin- edged dorsal aperture of the cochlear aqueduct which faces directly dorsally. The square- shaped cochlea is found sometimes in Za- _LLAIT_~ C rachis and Pomatodelphis but to a much less- Fig. 15. Squalodelphisfabianii (IGUP 26378). er extent than in the Squalodelphidae. Stereophotographs of right periotic: (A) dorsal The malleus ofthe Squalodelphidae shows view, (B) ventral view, (C) lateral view. Scale an apomorphic apical extension ofthe manu- x O.50. 18 AMERICAN MUSEUM NOVITATES NO. 2904

Phocageneus have a very well developed dorsal transverse process whereas the ventral process is very reduced. This condition does not exist in the Squalodontidae and in the Platanistidae where the atlas is known, and is tentatively considered as a synapomorphy of the Squalodelphidae. The atlas of Squalo- delphis is unknown, and this feature is only inferred to be present in that genus. Fig. 16. Squalodelphisfabianii (IGUP 26378); Among the Squalodelphidae, Squalodel- stereophotographs of right malleus in postero- phis and Phocageneus are more specialized medial view. Scale x 3. than Notocetus in several respects. The posterior teeth of Phocageneus and Squalodel- extremity and where it reaches the anterior phis resemble each other in lacking one or spine. This condition is absent in all the other several accessory cups on their posterior edge, odontocetes where the groove stops before whereas these are present in Notocetus. The the anterior extremity of the tympanic (fig. loss ofposterior accessory cusps is a character 17). This apparently unique feature could be derived from a primitive squalodont-like an- a synapomorphy of the Squalodelphidae. cestral tooth morphology and could be re- Furthermore, the atlas of Notocetus and garded as a synapomorphy of both genera. .i

A' /v ,p

A B C /I. K.

-E F Fig. 17. Tympanics of Platanistoidea in ventral view. (A) Prosqualodon (AMNH 29022), (B) No- tocetus (AMNH 29026); (C) Phocageneus (cast of USNM 21039), (D) Zarachis (cast of USNM 10485), (E) Pomatodelphis~~D(USNM 187414), (F) Platanista (MNHN 1870-79). Scale x 0.51. 1 987 DE MUIZON: NOTOCETUS VANBENEDENI 19

Fig. 18. Lateral view ofthe skull ofPomatodelphis cf. inaequalis (USNM 187414). For abbreviations see text. Scale x 0.33. (The maxillary-pterygoid-palatine suture has been outlined to enhance the position of the palatine.)

Furthermore, the articular rim is more de- cetes (Iniidae and Pontoporiidae) but they are veloped in Phocageneus and Squalodelphis always much smaller than in the Platanisti- than in Notocetus; it is, in fact, a small apoph- dae. Pilleri and Ghir (1979) reconstructed ysis which foreshadows the development of large maxillary crests in Ischyrorhynchus a hooklike articular process of the Platanis- vanbenedeni mainly inspired by the mor- tidae. In other respects, the tympanics ofPho- phology of Platanista. Their interpretation cageneus and Squalodelphis resemble each may be correct, but one could very well imag- other more than they do Notocetus, essen- ine a much less developed crest approaching tially in the greater length ofthe anterior spine. the condition observed in Inia. Nevertheless, (The lateral furrow is more distinct than in a more complete skull with complete max- Notocetus and the small longitudinal eleva- illary crest and associated auditory region and tion in the ventral groove recalls the ventral scapula is necessary to decide whether I. van- spine ofPlatanista and is absent in both tym- benedeni is related to the Platanistidae (sensu panics known for Notocetus.) These features de Muizon, 1984). Ifthe large maxillary crests in Phocageneus and Squalodelphis are de- are actually present in Ischyrorhynchus van- rived when compared to the condition in No- benedeni, this condition could also represent tocetus. Considering these synapomorphies, a parallelism with the platanistid anatomy Phocageneus and Squalodelphis are regarded instead ofan indication ofclose phylogenetic here as sister-genera and both constitute the relationship. However, in the absence of an sister-group of Notocetus. It should be also associated auditory region with a skull, the mentioned that the condition ofthe supraor- assignation of L vanbenedeni to the Inioidea bital process ofSqualodelphis, which is thick- remains uncertain (de Muizon, 1984: 75). er and hence more specialized than that in Another synapomorphy of the Platanisti- Notocetus, is anticipated for as yet unknown dae is represented by the structure ofthe pal- skulls of Phocageneus. atine bones. The palatine bones of the Plata- nistidae are not articulated medially. In Platanistidae contrast to their usual position in the other The Platanistidae are essentially defined by odontocetes, they show a clear dorsolateral the appearance of very high and large max- migration. The condition observed in Plat- illary or frontomaxillary crests. Similar struc- anista is even more specialized as the palatine tures may be found in some other odonto- is completely overlapped laterally by the 20 AMERICAN MUSEUM NOVITATES NO. 2904

in Platanista. Although restrictions could be made concerning some ofthese features, they are tentatively regarded as synapomorphies of Zarachis and Pomatodelphis (figs. 19, 20). Platanista is often regarded as a very primitive odontocete and sometimes as the most primitive among the living forms. However, as mentioned by Barnes et al. (1985), this genus shows many highly specialized features. Some characters commonly regarded as primitive could very well be due to re- Fig. 19. Pomatodelphis cf. inaequalis (USNM versals. The typical autapomorphic charac- 187414). Stereophotographs of left periotic: (A) ters of Platanista are: dorsal view, (B) ventral view, (C) lateral view. Scale x50. . 1. extreme development of the maxillary crests; pterygoid. The relationship ofthe platanistid 2. increase in the size ofthe zygomatic pro- palatine bones is unique among the odon- cess ofthe squamosal and the correlative tocetes and is regarded here as one of the reduction of the orbit; major synapomorphies of the family Plata- 3. well marked asymmetry of the vertex, nistidae (fig. 18). which is almost absent in the other Plata- The Platanistidae are also defined by the nistidae; reduction in length and transverse thickness 4. narrowness of the rostrum; of the medial lobe of the tympanic, by the 5. position of the palatines, covered ven- greater elevation of the lateral wall of the trally by the pterygoids; tympanic, by the transformation of the peri- 6. reduction of the articular portion of the otic articular rim ofthe Squalodelphidae into posterior process of the periotic; a hooklike articular process, and by the short- 7. development of the unciform process of ening and thickening of the anterior process the tympanic; of the periotic. 8. round internal auditory window; Among the Platanistidae, Zarachis and Po- 9. development ofa well differentiated spine matodelphis resemble each other more than of spongy bone in the ventral groove of they resemble Platanista, but precise syn- the tympanic; apomorphies are not easy to define, and most 10. increase in length of the crown of ante- ofthe similarities are symplesiomorphies. The rior teeth. supracranial crests are frontomaxillary in However, some features are obviously ple- Zarachis and Pomatodelphis while they are maxillary only in Platanista. Apparently, the siomorphic: frontomaxillary crests could be apomorphic 1. notable heterodonty; as compared to the maxillary crests of Plat- 2. lateral lamina ofthe pterygoid, which con- anista. However, the condition in that genus tacts the falciform process of the squa- could also be the result of a secondary regres- mosal, therefore forming a continuous lat- sion ofthe frontal part ofthe crest, a possible eral bony wall for the pterygoid sinus (see consequence of the great enlargement of the de Muizon, 1984: 39); maxillary crest. On the periotic, the apex of 3. double articulation of the tympanic with the anterior process is dorsoventrally thicker the squamosal and the periotic (see de in Zarachis and Pomatodelphis than in Plat- Muizon, 1984); anista. In some specimens the apex is even 4. small size ofthe mandibular foramen and square-shaped while it is more rounded in of the internal fossa for the fatty body of others, representing possible sexual dimor- the mandible; phism. Moreover, on the tympanic of Po- 5. unfused cervical vertebrae which have a matodelphis and Zarachis, the medial aspect longer centrum than in any other living ofthe involucrum is much more elevated than cetaceans. 1 987 DE MUIZON: NOTOCETUS VANBENEDENI 21

In other respects some features of Plata- nista seem to be apparently plesiomorphic but are tentatively regarded here as reversals: 1. lambdoidal crests inflected medially to A a much greater extent than in any other Plata- nistoidea; this morphology is a probable consequence of the development of very large maxillary crests and the zygomatic process of the squamosal; 2. elevation ofthe dorsal tuberosity ofthe posterior process ofthe periotic (absent in all the other Platanistoidea), which imbricates in the angle formed at the squamosal-occipital suture. This structure is probably related to the necessity for strengthening the attach- ment of the periotic to the skull in the Plata- nistidae, a function accomplished in the other Platanistidae and in Squalodelphidae by the development ofeither an articular process (as Fig. 20. Pomatodelphis cf. inaequalis (USNM in Platanista) or an articular rim. 187414). Stereophotographs of left tympanic: (A) lateral view, (B) medial view, (C) ventral view. Scale x0.S . PREVIOUS ASSIGNMENTS OF NOTOCETUS VANBENEDENI metry of the vertex of N. vanbenedeni was In the original description of N. vanbene- also regarded by Cabrera as a ziphiid char- deni, Moreno (1892) did not make a precise acter. Nonetheless, the same asymmetry is assignation of his specimen but compared it found in Squalodelphis and is more empha- to Pontoporia, Inia, and Squalodon. Ameghi- sized in Platanista, but is much less devel- no (1894) and Lydekker (1894) referred Mor- oped on True's specimen. In fact, this feature eno's specimen to the Platanistidae and Ly- reflects a general tendency of the Odonto- dekker regarded Notocetus vanbenedeni as a cetes, which is most pronounced in the Phy- primitive platanistid with squalodont fea- seterida (Physeteroidea + Ziphioidea). The tures. True (1910: 31) definitely related No- shallow facial depression, which according to tocetus vanbenedeni to the Squalodontidae al- Cabrera is a ziphiid character, is much more though he recognized that the species was not reduced than in the ziphiids and is similar to "so distantly related" to the ziphiids (True, that in Squalodon, Pomatodelphis, and Za- 1910: 21). Dal Piaz (1916b) created the fam- rachis. In fact, none of the characters cited ily Squalodelphidae which included the gen- by Cabrera are fully satisfactory and they are era Squalodelphis (established in the same either symplesiomorphies or features which paper) and Argyrodelphis (=Notocetus). He are easily attained through parallelism. Kel- concluded that there was a close affinity be- logg (1928: 58) did not comment much on tween the Squalodontidae and Squalodel- the ziphiid features of Notocetus, but he did phidae. find several similarities of this genus with Subsequently, Winge (1918, 1921), Ca- Squalodon. Among these is the stoutness of brera (1926), Kellogg (1928), and Simpson the zygomatic process of the squamosal, (1945) referred Notocetus to the Ziphiidae. which is also found in the Platanistidae (Plat- However, one of the typical ziphiid charac- anista, Zarachis, and Pomatodelphis) and ters given by Cabrera (1926: 392) (i.e., the Squalodelphis. The similarity was also noted inflation ofthe posterolateral part ofthe den- by Winge (1921: 38). taries) is also found in Squalodelphis, Squalo- The vertebrae of Notocetus vanbenedeni don, and some Rhabdostoidea. Moreover, this have often been regarded as typically ziphioid part of the mandible is very fragile and is (True, 1910; Winge, 1921; Cabrera, 1926; often distorted by fossilization. The asym- Kellogg, 1928). However, the ziphioid fea- 22 AMERICAN MUSEUM NOVITATES NO. 2904 tures noted by True (19 10) and Cabrera (1926) this character was absent from Sulakocetus, are also present in the squalodonts described this form would approach somehow the mor- by Dal Piaz (1916a). Moreover, the trans- phology of an hypothetical squalodont-like verse processes of the atlas of Notocetus is ancestor of the Ziphioidea and Physeteroi- distinct from the ziphiid condition. The dea. primitive condition is found in Squalodon, After Kellogg (1928), few references were Eurhinodelphis, or Zarachis where both dor- made about Notocetus vanbenedeni. Colbert sal and ventral transverse processes (resulting (1944), Simpson (1945), Dechaseaux (196 1), from the opening of the transverse foramen) Romer (1969), and Mead (1975) accepted the are approximately the same size. In the Del- assignment to the Ziphiidae without much phinoidea and Physeterida the dorsal trans- criticism. Recently, Barnes et al. (1985) have verse process almost completely disappears proposed a phylogeny of cetaceans in which and the ventral one is well developed. The the family Squalodelphidae is recognized as Inioidea (sensu de Muizon, 1985) have a an early derivation of the Squalodontidae. much reduced ventral transverse process Although the genus Notocetus is not dis- while the dorsal is only a little longer. In No- cussed in the text, it is apparently related to tocetus vanbenedenithe dorsal process is much that family and the ziphiid affinities are re- longer than the ventral and this condition is jected. In this respect I agree with the phy- therefore closer to that of the Inioidea than logeny given by Barnes et al. (1985) which, to that of the Ziphioidea. The condition in in other respects, strongly differs from the Phocageneus is the same as that in Notocetus. platanistoid phylogeny proposed here. Those In fact, the dorsal transverse processes ofNo- authors accept the monophyly of the Plata- tocetus and Phocageneus are much larger than nistoidea (sensu Simpson, 1945) and the in the Inioidea, and considering that it is perfamily Acrodelphidae is regarded as closely haps one of the few characters that could re- related to the Pontoporiidae. The Acrodel- late the Squalodelphidae to the Inioidea, it is phidae are considered by these authors to in- here regarded as a result ofparallel evolution. clude such genera as Pomatodelhis, Zara- In conclusion, the similarities ofNotocetus chis, and Schizodelphis. However, Bames et with both the Ziphiidae and Squalodontidae al. (1985: 20) mention that "for the sake of indicate that some relationships could exist the present discussion, we leave the family between Ziphiidae and Squalodontidae. This in the Platanistoidea, but it needs serious re- idea is not new; it has already been expressed evaluation," a statement I regard as very rea- by Abel (1905) and Kellogg (1928). This sonable. statement also suggests polyphyletic or paraphyletic nature ofthe Squalodontidae. In fact, NOTES ON THE ACRODELPHIDAE it is possible that the Ziphioidea and Phy- AND RHABDOSTOIDEA seteroidea have their origin in some squalodont-like odontocete. Most of the Squalo- In a recent publication (de Muizon, 1984), dontidae bear the synapomorphies of the I related the Acrodelphidae to the Rhabdo- scapula identified above. However, we have stoidea. The Acrodelphidae were thought to seen that Sulakocetus still retains a coracoid include the genera Acrodelphis, Schizodel- process, whereas it is lost in the other Plata- phis, Eoplatanista, and Champsodelphis. As nistoidea. At the same time, Sulakocetus ap- I stated, the monophyly of the Rhabdosto- pears to have an acromion located on the idea and that of the Acrodelphidae have yet anterior edge ofthe bone. In this respect, this to be demonstrated by synapomorphies. Fur- bone would differ from the scapula of the thermore, the genera Schizodelphis, Acrodel- Physeterida where the supraspinous fossa is phis, and Champsodelphis have to be recon- sometimes nearly absent but where the base sidered. Here I briefly expose the major ofthe acromion is lateral to the anterior edge problems concerning these taxa which will be of the bone. However, the scapula of the ho- analyzed in detail elsewhere (de Muizon, in lotype of Sulakocetus is very poorly pre- prep.). served and it is not easy to determine pre- The type specimen of Schizodelphis sul- cisely the scapular condition in this genus. If catus (Gervais, 1848-52) is an incomplete 1987 DE MUIZON: NOTOCETUS VANBENEDENI 23 skull (MNHN RL12) from Cournonsec (De- its malleus is identical to that of Eurhino- partment of Herault, France) which has lost delphis. In other respects, it is different from both its periotics and tympanics during fos- the auditory region illustrated by Dal Piaz silization, and whose vertex and occipital re- (1903) and therefore the malleus of MNHN gion were destroyed during excavation. Abel RLl 1 that I figured elsewhere (de Muizon, (1900) and Dal Piaz (1903) referred skulls 1985: fig. 1) is not that of an Acrodelphidae from the Vienna basin and from Belluno (It- but that of a Rhabdosteidae. aly) to Gervais' species but assigned them a Consequently, Schizodelphis is a possible new genus name: Cyrtodelphis Abel 1900. rhabdosteid distinct from Eoplatanista, which This latter name is a junior synonym of is related to the Acrodelphidae. The lack of Schizodelphis Gervais 1861 (Eastmann, 1907; information on the vertex and the auditory Winge, 1921; Kellogg, 1928; Simpson, 1945; region of the holotype of Schizodelphis sul- Romer, 1969; Pilleri, 1985). In other re- catus perhaps requires one to consider this spects, the holotype ofSchizodelphis sulcatus species as an incertae sedis taxon. (with further preparation) is generically dif- Among the Acrodelphidae, the genus Ac- ferent from the specimens figured by Abel rodelphis was established by Abel (1900) for (1900), Dal Piaz (1903), and Pilleri (1985) several species ofthe genus Champsodelphis. and shows greater similarities to the Rhab- No type species was formally named by Abel, dosteidae; it resembles some Rhabdosteus and so one must consequently choose the old- specimens from the Calvert formation of est species referred by that author to Acro- Maryland (USA) revised by Myrick (1979). delphis: A. macrognathus (Brandt, 1873). This Furthermore, Eoplatanista italica Dal Piaz species was originally referred by Brandt to (1916c) shows striking similarities with the the genus Champsodelphis Gervais 1848-52. specimens referred by Abel, Dal Piaz, and However, this species is a junior synonym of Pilleri to Cyrtodelphis sulcatus or to Schizo- Champsodelphis macrogenius (Laurillard, delphis sulcatus. The auditory regions are 1844). The latter species name was created identical and the skulls are otherwise mor- by Laurillard for both specimens recorded by phologically very similar. I consider Abel's, Cuvier (1823) as "Dauphin a longue sym- Dal Piaz's, and Pilleri's specimens to belong physe" which are a portion ofmandible with to the genus Eoplatanista, and I regard the part of the symphysis (Cuvier, 1823: pl. 23, species of Schizodelphis brachycephalus Pil- figs. 4, 5) and a portion of rostrum (Cuvier, leri 1985 as ajunior synonym ofEoplatanista 1823: pl. 23, figs. 9-11). Because Cuvier's italica Dal Piaz 1916c (this conclusion will name makes reference to the mandible and be further developed in a work in prepara- Laurillard mentions the mandible first in his tion). formal designation of "Delphinus" macro- Two other remarks are noteworthy. First, genius, the lower jaw must therefore be re- it is true that the illustration given by Abel garded as the lectotype of that species. (1900: pl. 3, figs. 2-4) for the tympanic he Champsodelphis macrognathus Brandt 1873, refers to Schizodelphis (=Cyrtodelphis) sul- based on this specimen, is therefore a junior catus indicates obvious squalodelphid affin- synonym of Champsodelphis macrogenius ities. However, Dal Piaz (1903: 204), who (Laurillard, 1844). The genus Acrodelphis studied the specimen, mentions that Abel's Abel 1900 is consequently a junior synonym illustrations are not accurate and that a com- ofChampsodelphis Gervais (1848-52) as both parison of the Eggenburg tympanic with the genera have the same type species. The fam- Belluno tympanic shows strong morpholog- ily Acrodelphidae should have the same fate ical affinities. Second, Van Beneden and Ger- as its type genus, but, as it is not the purpose vais (1880: pl. 57, fig. 8) illustrated an au- of this paper to revise this group of odon- ditory region ofan odontocete (MNHN RLl 1) tocetes, the family is provisionally retained from the Castries shales (Department of He- here in the sense of de Muizon (1984). Ac- rault, France) and they referred the specimen rodelphis ombonii (Longhi, 1898) is based on to Schizodelphis sulcatus without explana- a partial skull with associated auditory re- tion. In fact, this specimen is very similar to gion, and must be given a new genus name the periotic and tympanic ofRhabdosteus and (de Muizon, in prep.); its auditory region, 24 AMERICAN MUSEUM NOVITATES NO. 2904 illustrated by Dal Piaz (1977) and Pilleri tina. The first detailed description of its au- (1985), seems to indicate some affinities with ditory region and scapula indicates the pres- the Squalodelphidae but a detailed study of ence of synapomorphies which relate the this form is needed to settle that point. species to the superfamily Platanistoidea and The type specimen of the type species of to the family Squalodelphidae. This hypoth- the genus Champsodelphis (i.e., the lectotype esis disagrees with the long-believed affinity ofC. macrogenius designated above) is a por- of Notocetus to the Ziphiidae but acknowl- tion of mandible which is regarded as totally edges the similarities of this genus with the inadequate to define an odontocete cetacean. Squalodontidae recognized by all authors Consequently, the genus Champsodelphis and since the original description by Moreno the species C. macrogenius must be regarded (1892). As a matter of fact, Squalodontidae either as nomina vana or as incertae sedis is regarded here as the sister-group of the restricted to the type specimen. Given that monophyletic assemblage formed by the the skull described by Delfortrie (1875) as C. Squalodelphidae and the Platanistidae. The tetragorhinus cannot be seriously referred to three families are considered to constitute the Champsodelphis, "C." tetragorhinus, which monophyletic superfamily Platanistoidea is known by a fairly complete skull but with- (sensu de Muizon, 1984, 1985). out an associated auditory region, must Notocetus vanbenedeni shows synapomor- therefore be given a new genus name. The phies of the Platanistoidea: squamosal morphology and the thickened su- 1. loss ofthe coracoid process ofthe scapula; praorbital process of that species strongly 2. loss of the supraspinous fossa with the suggest squalodelphid affinities. As the orig- acromion located on the anterior edge of inal specimen was not observed during this the bone. study, "C." tetragorhinus will not be taken into account here, although it could be ten- N. vanbenedeni shows synapomorphies of tatively classified in the Squalodelphidae. The the Platanistidae-Squalodelphidae group: Acrodelphidae therefore include two well de- 1. development of a supplementary articu- fined genera only: "Acrodelphis" ("A." om- lation on the lateral side of the posterior bonii) and Eoplatanista; however, as stated process of the periotic (this structure is a above, the monophyly of that family still re- thick and salient articular rim which will mains to be established by synapomorphies. transform into a hooklike process in the Rhabdosteidae is defined by an important Platanistidae); shortening of the mandible relative to the 2. occurrence of a large subcircular fossa rostrum and the concurrent loss of its cor- dorsal to the spiny process of the squa- responding anterior teeth. This feature is mosal; absent in Eoplatanista. Rhabdostoidea 3. development of an anterior spine on the (Rhabdosteidae + Acrodelphidae), whose tympanic with a well marked anterolateral monophyly has still to be demonstrated, has convexity, separated from the spine by a been related to the Delphinidae on the basis notable notch; and oftwo synapomophies (de Muizon, 1984): (1) 4. single-rooted teeth. the palatine bones are slightly in contact with N. vanbenedeni shows features tentatively the anterior extremity of the pterygoid sinus regarded as synapomorphies of the Squalo- but no palatine lateral lamina is present and delphidae: (2) the articulation ofthe squamosal and tympanic is lost. 1. square-shaped cochlea of the periotic; With the exception of some of the generic 2. wide and thin-edged dorsal opening ofthe affinities, the platanistoid phylogeny pre- cochlear aqueduct; sented here is in general agreement with what 3. apical extension ofthe manubrium ofthe I have proposed elsewhere (de Muizon, 1984, malleus; 1985). 4. development ofthe dorsal transverse process of the atlas and reduction ofthe ven- SUMMARY AND CONCLUSIONS tral process. Notocetus vanbenedeni is an early Miocene Among the Squalodelphidae, the genus odontocete from Patagonia, southern Argen- Notocetus is the sister-group of the group 1 987 DE MUIZON: NOTOCETUS VANBENEDENI 25

Squalodelphis + Phocageneus which is relat- which probably represent symplesiomor- ed by the loss of accessory cusps of the pos- phies. Also, similarities with the Oligocene terior teeth, the more developed articular rim, forms like Patriocetus, Agorophius, or Xe- the greater length of the anterior spine of the norophus are obvious. It is therefore clear tympanic, the better marked lateral furrow, that the squalodonts are perhaps the odon- and the occurrence of a small longitudinal tocete group in most need of a serious revi- elevation in the ventral groove of the tym- sion. Such a study would certainly shed light panic. on the understanding ofthe evolution ofearly The Squalodelphidae include the following odontocetes and on the origin of the living genera: Notocetus (the most primitive) from groups. the Early Miocene of Patagonia, Squalodel- phis from the Middle Miocene of Italy, and REFERENCES CITED Phocageneus from the Middle Miocene of Abel, 0. the Calvert Formation (Maryland, USA). 1900. Untersuchungen uiber die fossilen Another form ofSqualodelphidae is from the Platanistiden des Wiener Beckens. Middle Miocene of the Pungo River For- Denkschr. Kaiser. Akad. Wiss., 68: 839- mation at Lee Creek Mine in North Carolina; 874. it is known from periotics and tympanics and 1905. Les odontocetes du Bolderien (Miocene superieur) d'Anvers. Mem. Mus. R. Hist. is under study by F. C. Witmore. A probably Nat. Belgique, 3: 1-155. new species ofNotocetus is reported from the Ameghino, F. Middle Miocene of the Calvert Formation, 1891. Caracteres diagnosticos de cincuenta es- thus extending the range of that genus to the pecies nuevas de mamiferos fosiles ar- Middle Miocene of the Northern Hemi- gentinos. Cetacea, Odontoceta, Sauro- sphere. cetidae. Rev. Argentina Hist. Nat., 1: The Platanistidae are mainly defined by the 163-165. acquisition of strongly developed maxillary 1894. Enumeration synoptique des especes de or frontomaxillary crests on the supraorbital mammiferes fossiles des formations regions of the skull. This structure is never Eocenes de Patagonie. Bol. Acad. Cienc. (Cordoba), 3: 259-452. found with such an extension in any other Barnes, L. G., D. P. Domning, and C. E. Ray cetacean. The Platanistidae are also defined 1985. Status of studies on fossil marine mam- by synapomorphies relating to the periotic mals. Mar. Mammal Sci., 1(1): 15-53. and tympanic. This family includes: the liv- Bourdelle, E., and P. P. Grasse ing genus Platanista and the Middle Miocene 1955. Ordre des Cetaces. In Traite de zoolo- genera, Zarachis and Pomatodelphis from the gie, vol. 27, pp. 341-450. Paris: Masson Calvert Formation and for the latter also & Cie. (Middle to late Miocene) from the lower Bone Brandt, J. F. Valley Formation of Florida. 1873. Untersuchungen fiber die fossilen und No is to define the subfossilen Cetaceen Europas. M6m. synapomorphy given Acad. Sci. St. Petersbourg, VII ser., Squalodontidae, an apparently conservative 20(1): 1-372. group. This family is "defined" only by sym- Cabrera, A. plesiomorphies, and could well be a para- 1926. Cetaceos fosiles del Museo de La Plata. phyletic or even polyphyletic taxon. Most of Rev. Mus. La Plata, 29: 363-411. the Squalodontidae are referred to the Plata- Colbert, E. H. nistoidea because of synapomorphies of the 1944. A new fossil whale from the Miocene of scapula. Sulakocetus could, however, be ex- Peru. Bull. Am. Mus. Nat. Hist., 83(3): cluded from that superfamily (see above). 195-216. Moreover, the striking similarities between Cuvier, G. the and the seem 1823. Recherches sur les ossemens fossiles oiu Squalodontidae Ziphiidae l'on retablit les caracteres de plusieurs to indicate a squalodont-like morphology for animaux dont des revolutions du globe the ancestors of that family and probably of ont detruit les especes. In G. Dufour & the Physeteroidea. The platanistoid affinities E. d'Ocagne (eds.), Paris nouv. edit., 5(1): of the squalodonts have been documented 1-405. here, but it is noteworthy that this group shows Dal Piaz, G. some similarities with the Rhabdostoidea 1903. Sugli avanzi di Cyrtodelphis sulcatus 26 AMERICAN MUSEUM NOVITATES NO. 2904

dell'arenaria di Belluno. Paleont. Ital., phinoides; l'autre le genre Dinocyon de 9: 187-219. l'ordre des Carnassiers et de la famille 1916a. Gli Odontoceti del Miocene Bellunese, des Canides. Ann. Sci. Nat., ser. 4, Zool., parte seconda, Squalodon. Mem. Ist. 16: 369-372. Geol. Univ. Padova [publ. dal G. Dal Kasuya, T. Piaz], 4: 1-94. 1973. Systematic consideration of Recent 1916b. Gli Odontoceti del Miocene Bellunese. toothed whales based on the morphol- Parte Hershkovitz, P. 1966. Catalog of ogy of tympanoperiotic bone. Sci. Rep. living whales. Bull. U.S. Winge, H. ter- Whales Res. Inst., 25: 1-103. za, Squalodelphisfabiani. Ibid., 5: 1-34. Kellogg, R. 1916c. Gli Odontoceti del Miocene Bellunese. 1928. The history ofwhales. Their adaptation Parte quarte, Eoplatanista italica. Ibid., to life in the water. Q. Rev. Biol., 3(1): 4: 1-23. 29-76. 1917. Gli Odontoceti del Miocene Bellunese. 1957. Two additional miocene porpoises from Parti Quinta-decima Cyrtodelphis, Ac- the Calvert Cliffs, Maryland. Proc. U.S. rodelphis, Protodelphinus, Ziphiodel- Nat. Mus., 107: 279-337. phis, Scaldicetus. Ibid., Allegato al vol. Laurillard, F. L. 4(1916): 1-128. 1844. Dauphins fossiles. In A. d'Orbigny (dir.), Dechaseaux, C. Dictionnaire universel d'histoire natu- 1961. Cetacea. In Traite de paleontologie, vol. relle, t. 4, pp. 634-636. Paris: Bureau 6, pp. 831-886. Paris: Masson & Cie. Principal des Editeurs. Delfortrie, E. Longhi, P. 1875. Un dauphin d'espece nouvelle dans les 1898. Sopra di reste du un cranio di Champ- faluns du sud-ouest. Actes Soc. Linn. sodelphis fossile scoperto nella molassa Bordeaux, 30(2): 3-7. miocenica del Belluneuse. Atti Soc. Ve- Eastman, C. R. neto Trentina. Sci. Nat., ser. 2, 3(2): 1- 1907. Types offossil cetaceans in the Museum 59. of Comparative Zoology. Bull. Mus. Lyddeker, R. Comp. Zool., 51(3): 79-94. 1894. Contribution to the knowledge of the Fordyce, R. E. fossil vertebrates of Argentina. Part II. 1983. Rhabdosteid dolphins (Mammalia, Ce- Cetacean skulls from Patagonia. An. tacea) from the Middle Miocene, Lake Mus. La Plata, 2: 1-15. Frome area, South Australia. Alcherin- MacFadden, B. J., K. E. Campbell, R. L. Cifelli, ga, 7: 27-40. 0. Siles, N. M. Johnson, C. W. Naeser, and P. Fraser, F. C., and P. E. Purves K. Zeitler 1960. Hearing in Cetaceans evolution of the 1985. Magnetic polarity stratigraphy and accessory air sacs and the structure and mammalian fauna ofthe Deseadan (Late function of the outer and middle ear in Oligocene-Early Miocene) Salla beds of Recent Cetaceans. Bull. Br. Mus. (Nat. northern Bolivia. J. Geol., 93: 223-250. Hist.) Zool., 7(1): 1-140. Marshall, L. G., R. Hoffstetter, and R. Pascual Frenguelli, J. 1983. Mammals and stratigraphy: geochro- 1927. El Entrerriense de Golfo nuevo en el nology of the continental mammal- Chubut. Bol. Acad. Nac. Cienc. (Cor- bearing Tertiary of South America. doba), 29: 191-270. Palaeovertebrata, Mem. Extraord., pp. Gervais, P. 1-93. 1848-52 Zoologie et paleontologie fran9aises Marshall, L. G., R. E. Drake, G. H. Curtis, R. F. (animaux vertebres) ou nouvelles re- Butler, K. M. Flanagan, and C. W. Naeser cherches sur les animaux vivants et fos- 1986. Geochronology of type Santacrucian siles de la France, vol. 1, pp. 1-271. (Middle Tertiary) land mammal age, Arthus Bertrand ed.: Paris. Patagonia, Argentina. J. Geol., 94(4): Hershkovitz, P. 449-457. 1966. Catalog ofliving whales. Bull. U.S. Nat. Mchedlidze, G. A. Mus., 246: 1-259. 1976. Osnovnyye cherty paleobiologicheskoi Jourdan, C. istorii Kitoobraznykh (basic features of 1861. Description de restes fossiles de deux the paleobiological history of the Ce- grands Mammiferes constituant deux tacea). Akad. Nauk Grurinskoi SSR, genres, l'un le genre Rhizoprion de Inst. Paleobiol. "Metsniereba" Press, pp. l'ordre des Cetaces et du groupe des Del- 1-112 [in Russian, English summary]. 1987 DE MUIZON: NOTOCETUS VANBENEDENI 27

1984. General features ofpaleobiological evo- Rice, W. D. lution of Cetacea. Russian translation. 1968. A list of the marine mammals of the Prem Pritting Press, Lucknow (India), world. NOAA Technical Report NMSF 23: 1-139. SSRF, 711: 1-15. Mead, J. G. Romer, A. S. 1975. A fossil beaked whale (Cetacea: Ziphi- 1969. Vertebrate paleontology, 4th ed. Chi- idae) from the Miocene ofKenya. J. Pa- cago: Univ. ofChicago Press, pp. 1-468. leontol., 49: 745-751. Rothausen, K. Moreno, F. P. 1968. Die systematische Stellungder euro- 1892. Noticias sobre algunos cetaceos fosiles piiischen Squalodontidae (Odontoceti, y actuales de la Republica Argentina. Mamm.). Paliiontol. Z., 42: 83-104. Rev. Mus. La Plata, 3: 381-400. Simpson, G. G. Muizon, C. de 1935. Early and middle tertiary geology ofthe 1984. Les vertebres fossiles de la Formation Gaiman region, Chubut, Argentina. Am. Pisco (Perou). Deuxieme partie: Les Mus. Novitates, 775: 29 pp. Odontocetes (Cetacea, Mammalia) du 1945. The principles of classification and a Pliocene inferieur de Sud-Sacaco. Trav. classification of mammals. Bull. Am. Inst. Fr. Et. Andines, vol. 27, pp. 1-188. Mus. Nat. Hist., 85: 1-350. In Rech. sur Civ., mem. 50, ADPF, True, F. W. Paris. 1910. Description on a skull and some ver- 1985. Nouvelles donnees sur le diphyletisme tebrae of the fossil cetacean Diochoti- des Dauphins de riviere (Odontoceti, chus vanbenedeni from Santa Cruz, Pat- Cetacea, Mammalia). C. R. Acad. Sci., agonia. Ibid., 28(4): 19-32. Paris, ser. II, 301: 359-362. Van Beneden, P. J., and P. Gervais Myrick, A. C., Jr. 1880. Osteographie des Cetaces actuels et fos- 1979. Variation, taphonomy, and adaptation siles. Arthus Bertrand Atlas, 634 pp. 64 of the Rhabdosteidae (= Eurhinodel- pIs. phidae (Odontoceti, Mammalia) from Whitmore, F. C., and A. E. Sanders the Calvert Formation ofMaryland and 1977. Review of the Oligocene Cetacea. Syst. Virginia. Ph.D. dissertation, Univ. of Zool., 25(4): 304-320. California, Los Angeles, 437 pp. Winge, H. Pilleri, G. 1918. Udsigt over Hvalernes indbyrdes 1985. The Miocene Cetacea of the Belluno Slaegtskab. Vidensk. Medd. Dan. sandstone. Mem. Ist. Geol. Univ. Pa- Naturhist. Foren., 70: 59-142. dova, 36: 1-87. 1921. A review ofthe interrelationships ofCe- Pilleri, G., and M. Ghir tacea. Smithson. Misc. Collect., 72(8): 1979. Skull, sonar field and swimming behav- 1-98. ior of Ischyrorhynchus vanbenedeni Zhou, K. (Ameghino 1899) and taxonomical po- 1982. Classification and phylogeny of the su- sition of the genera Ischyrorhynchus, perfamily Platanistoidea, with notes on Saurodelphis, Anisodelphis and Ponto- evidences of the monophyly of the Ce- planodes (Cetacea). In G. Pilleri (ed.), tacea. Sci. Rep. Whales Res. Inst. To- Investigation on Cetacea, vol. 10, pp. kyo, 34: 93-108. 17-78. Recent issues of the Novitates may be purchased from the Museum. Lists of back issues of the Novitates, Bulletin, and Anthropological Papers published during the last five years are available free of charge. Address orders to: American Museum of Natural History Library, Department D, Central Park West at 79th St., New York, N.Y. 10024.