PaleoBios 23(3):21–35, December 15, 2003 © 2003 University of California Museum of Paleontology

The first report of hard-shelled sea turtles (Cheloniidae sensu lato) from the Miocene of California, including a new species (Euclastes hutchisoni) with unusually plesiomorphic characters SHANNON COLLEEN LYNCH1and JAMES FORD PARHAM2 Department of Plant Pathology, 1 Shields Avenue, 371 Hutchison Hall; University of California, Davis; Davis, California 95616; [email protected]. 2University of California Museum of Paleontology, 1101 Valley Life Sciences Building; University of California, Berkeley; Berkeley, California 94720; [email protected] 1

In this paper we describe the first cheloniid turtle fossils from the Miocene (Barstovian) of California, USA. All specimens are from Sharktooth Hill, Round Mountain Silt Member of the marine Temblor Formation, in Kern County. The material includes two species: (1) a form with a sculptured carapace (cf. Syllomus) known from a single specimen; (2) a form with unusually plesiomorphic characters including a wide plastron, a Toxochelys Toxochelys-like humerus, femoral trochanters separated by a deep fossa, a broad sutural contact between the vomer and premaxillae on the palatal surface, and a single facet on the anterior end of the eighth cervical vertebra. This second sea turtle can be differentiated from other cheloniid taxa and so is named a new species, Euclastes hutchisoni. A cladistic analysis of 13 cheloniid taxa and 34 morphological characters suggests a phylogenetic position of Euclastes hutchisoni far-removed from the living cheloniids. Euclastes hutchisoni appears to be the last member of a Cretaceous-Paleocene radiation of durophagous stem cheloniids.

INTRODUCTION In this paper we describe the first cheloniid turtle fossils from the Miocene of California, USA. The material includes several specimens of a new species of cheloniid sea turtle, Euclastes hutchisoni. In addition to E. hutchisoni hutchisoni, we describe one specimen (UCMP V69169/88516) that superficially resembles Syllomus Cope 1896. All of the specimens described below are from Sharktooth Hill, Round Mountain Silt Member of the marine Temblor Formation, in Kern County, California. Sharktooth Hill is considered to be middle Miocene (~13–15 m.y.o., Barstovian North American land mammal age, “Temblor” provincial molluscan stage, Relizian or Luisian foraminferal stage; Evernden et al. 1964, Berggren and Van Couvering 1974, Barnes 1976, 1978, Repenning and Tedford 1977, Barnes and Mitchell 1984). Sharktooth Hill well known for its abundant shark teeth and marine mammal specimens (Mitchell 1965, 1966, Mitchell and Tedford 1973, Barnes 1976). The only preexisting work on marine turtle material from Sharktooth Hill is a short note by Gilmore (1937). In that paper, Gilmore erects a new taxon, Chelonia? californiensis californiensis, for an isolated turtle femur (CAS 4379). The figures of this specimen show that it belongs to a dermochelyid turtle close to “Psephophorus” Psephophorus Psephophorus” calvertensis Palmer 1909 from the Calvert Formation of Maryland, a formation that is approximately the same age as Sharktooth Hill (Ray 1976, Barnes and Mitchell 1984). Personal observation of large numbers of undescribed specimens of a large dermochelyid from Sharktooth Hill (at the BVM) support the hypothesis that the Temblor and Calvert dermochelyids are conspecific, but detailed study is needed. The fragmentary remains of this leatherback are a common component of Sharktooth Hill sediments, though considerably less abundant than the sharks (teeth) or marine mam-

mals. Specimens of hard-shelled sea turtles (Cheloniidae sensu lato) are relatively more rare. Taxonomy of hard-shelled sea turtles (Cheloniidae sensu lato) The taxonomy of hard-shelled sea turtles is constantly changing. For the sake of clarity, we provide a detailed explanation of the taxonomy used by this study. We use a phylogenetic taxonomy (de Queiroz and Gauthier 1990, 1992) a system previously restricted to a few turtle studies (Lee 1995, 1997, Parham and Fastovsky 1997). Parham and Fastovsky (1997) phylogenetically codified Cheloniidae Bonaparte 1832 to match the usage of the recent systematic works (Hirayama 1992, 1994, Hirayama and Chitoku 1996, Hirayama 1998). They gave Cheloniidae a stem-based definition as “those turtles that share a more recent common ancestor with extant marine turtles (exclusive of Dermochelys) than with Dermochelys or Protostega.” Parham and Fastovsky (1997) called the crown group of cheloniids “Cheloniinae”. Following the arguments presented by Rowe and Gauthier (1992), we feel that the crown group should receive the most common name: Cheloniidae. Unfortunately, this causes an inconsistency with previously published systematic works. We compromise by using Cheloniidae sensu lato for the stemdefinition of Cheloniidae and Cheloniidae sensu stricto for the crown-group name. This system was first used by Lapparent de Broin (2001). Osteopygis, Osteopyginae, and Euclastes Osteopygis Euclastes—The name Osteopygis Cope 1870 and its derivatives (Osteopyginae Zangerl 1953, Osteopygidae Gaffney and Meylan 1988) have long been associated with fossil specimens of Late Cretaceous and Paleogene cheloniid s.l. marine turtles showing adaptations for durophagy. During ongoing studies of eucryptodiran

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turtles, one of the authors discovered that the type specimen of Osteopygis (AMNH 1485, a shell) is not cheloniid s.l., but represents a “macrobaenid” (Parham unpublished data). “Macrobaenids” are poorly known turtles that first appear in the Early Cretaceous of Asia and persist until the Paleocene of Asia and North America (Sukhanov 2000, Parham and Hutchison in press). The skull of Osteopygis is unknown. Thus, we do not use Osteopyginae or Osteopygidae for the assemblage of taxa that included the skull material referred to Osteopygis and five monotypic skull-based genera (Euclastes Cope 1867, Glossochelys Seeley 1871, Erquelinnesia Dollo 1887, Osteopygoides Karl, Tichy and Ruschak 1998, and Pampaemys de la Fuente and Casadío 2000). Given the overall similarity of the material upon which these generic names are based, we place all of these skull genera into the oldest available name: Euclastes (see Appendix I). We do this because the sea turtle skulls referred to Osteopyginae require names and because it is not helpful to create additional monotypic genera for Euclastes hutchisoni, hutchisoni Osteopygis roundsi Weems 1988, and the skull material traditionally referred to Osteopygis emarginatus Cope 1868. Our phylogenetic definition of Euclastes is “those taxa that share a more recent common ancestor with Euclastes platyops Cope 1867 than to Chelonia Brongniart 1800, Argillochelys Lydekker 1889a, or Puppigerus Cope 1870”. Euclastes is diagnosed by the derived features of an extensive secondary palate and wide skull (Zangerl 1953, Fastovsky 1985, Gaffney and Meylan 1988, Hirayama 1994, Hirayama and Chitoku 1996, Parham and Fastovsky 1997, Hirayama 1998), as well as the retention of plesiomorphic features such as a broad suture between the vomer and the premaxillae, unfused trochanters of the femora, humerus with a proximal lateral process, plastra wider than long, and a single anterior facet on the eighth cervical vertebra. In many respects, Euclastes is evocative of the living Caretta Merrem 1820, though Caretta exhibits all the derived features of the crown group (Cheloniidae s.s.) and none of the plesiomorphies just mentioned. Parham and Fastovsky (1997) noted that the supposedly derived features of Euclastes might be the result of functional convergence for durophagy, but there are no data to support that hypothesis at this time. Two species incorrectly referred to Osteopygis warrant more detailed taxonomic discussion. Osteopygis sculptus Staesche 1929, from the Paleocene of Argentina, is based on the material of a pleurodiran turtle (de Broin and de la Fuente 1993). Apparently unaware of this, Karl et al. (1998) tentatively referred a partial skull of a cheloniid s.l. (SFMF Nr. R 4151) from the Late Cretaceous Quiriquina Formation of Chile to Osteopygis aff. sculptus. We refer to this specimen and an isolated dentary referred to Osteopygis by Gasparini and Biro-Bagoczky (1986) as the Quiriquina Euclastes. Osteopygis salisburgensis Karl 1996 is based on a partial shell from the Eocene of Austria that does not match the “macrobaenid” Osteopygis. We consider this species to be a cheloniid s.l. of indeterminate affinities. Though the generic assignment is clearly wrong, the specific epithet may be valid.

Institutional Abbreviations: AMNH, American Museum of Natural History, New York; ANSP, Academy of Natural Sciences of Philadelphia; BPBM, Bernice P. Bishop Museum; BVM, Buena Vista Museum of Natural History; CAS, Museum of the California Academy of Science, Paleontology; CNHM, Field Museum of Natural History (Chicago Natural History Museum); GHUNLPam, la Cátedra de Geología Histórica y Regional, Universidad Nacional de la Pampa; IGPS, Institut für Geologie und Paläontologie der Universität Salzburg; I.R.Sc.N.B., Institut Royal des Sciences Naturelles Belgique; LACM, Los Angeles County Museum of Natural History; SFMF, Forschungsinstitutund Museum Senckenberg Frankfurt am Main; S.M.C., Sedgwick Museum, Cambridge; UCMP, University of California Museum of Paleontology, Berkeley; USNM, United States National Museum. SYSTEMATIC PALEONTOLOGY TESTUDINES Batsch 1788 CRYPTODIRA Cope 1868 CHELONIIDAE sensu lato Bonaparte 1832 EUCLASTES Cope 1867 Emended diagnosis—Unlike Toxochelys Cope 1873 and Eochelone Dollo 1903 based on the presence of a secondary palate. Different from Ctenochelys Zangerl 1953 by the extent of the secondary palate. Distinguished from other cheloniids s.l. based on: (1) broad skull; (2) low skull profile; (3) broad and flat palatal surface; (4) low tomial ridge; (5) wide, flat dentary; (6) dentary with an elongated symphysis. EUCLASTES Cope 1867 EUCLASTES HUTCHISONI sp. nov. Holotype—LACM 103351 (Figs. 2–4), a nearly complete skull and mandible. Referred Materials—Figures 4–8. BVM 0810, a partial skeleton including a mandible, a partial plastron, three cervical vertebra elements, four costals, a pygal, and seven peripherals; BVM 0806, BVM 0805 and UCMP V69169/ 98202, all dentaries; BVM 0532, left humerus; BVM 0807, complete humerus; BVM 0472, nearly complete humerus, missing the distal end; UCMP V6024/65617, complete humerus; UCMP V6843/88343, complete humerus; UCMP V6843/86024, proximal humerus; UCMP V68131/85318, proximal humerus fragment; UCMP V68131/97116, humerus; UCMP V6323/88367, proximal humerus; UCMP V69169/88379, proximal humerus; BVM 0471, large complete femur; BVM 0535, femur; BVM 0809, proximal femur, BVM 0808 proximal femur; UCMP V6323/88364, femur; UCMP 1292/61576 proximal femur. Locality and Horizon—All specimens are from Sharktooth Hill, Kern County, California. Round Mountain Silt member of the Temblor Formation, middle Miocene (Barstovian). The holotype is from LACM locality 3162. Diagnosis—Unlike the four of the six named species of Euclastes (Euclastes platyops Cope 1867, Euclastes gosseleti

LYNCH & PARHAM PARHAM—HARD-SHELLED SEA TURTLES [Dollo 1886], Euclastes roundsi [Weems 1988], Euclastes priscus [Karl, Tichy, and Ruschak 1998]) based on the presence of an incised palatal surface of the premaxillae. Secondary palate not as extensive as Euclastes meridionalis (de la Fuente and Casadío 2000). Skull not as high or wide as Euclastes planimenta Owen 1842 and orbits not as dorsally facing. Etymology—The specific epithet, hutchisoni hutchisoni, is for J. Howard Hutchison of the University of California Museum of Paleontology, a respected fossil collector, artist, and expert on fossil turtles, moles, and shrews. CHELONIIDAE sensu lato Bonaparte 1832 cf. SYLLOMUS AEGYPTIACUS Lydekker 1889b Trachyaspis aegyptiaca Lydekker 1889b Syllomus crispatus Cope 1896 Peritresius virginianus Berry and Lynn 1936 Kurobechelys tricarinata Shikama 1956 Material—UCMP V69169/88516, fragment of costal with distinct sculpturing. Because the costals referred to E. hutchisoni (Fig. 6B) lack sculpture, we conclude UCMP 88516 represents another taxon. UCMP 88516 exhibits a dorsal sculpturing (Fig. 1) similar to that seen in Syllomus Cope 1896. The name Syllomus is commonly used to refer to an enigmatic species of pseudodont cheloniid s.l. known from Miocene deposits worldwide (Weems 1974, 1980, Zug 2001). Lapparent de Broin (2001) raises the possibility that the name Trachyaspis von Meyer 1843 may be an objective senior synonym of Syllomus. However, the type species of Trachyaspis (Trachyaspis lardyi von Meyer 1843) is only known from a few shell fragments. Lacking more complete material, or even a more detailed comparison, we tentatively retain the name Syllomus while encouraging future investigation into the problem.

1 cm Fig. 1. cf. Syllomus Syllomus, UCMP 88516, proximal costal fragment in dorsal view showing sculptured surface.

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DESCRIPTION OF EUCLASTES HUTCHISONI Description of Holotype, LACM 103351 (Figs. 2–4) The type of Euclastes hutchisoni is a skull and mandible (LACM 103351). Although the braincase and otic region are almost entirely missing, LACM 103351 provides adequate detail for description and determination of taxonomic affinities. The left side of the skull roof (the cheek region) is missing, but the right side of skull is mostly complete. The skull (14.5 cm preserved length) is broad and subtriangular in dorsal view, widest at the postorbitals (11.5 cm). The posterior portion of the skull roof is represented by the parietals posteriorly and a small portion of a broken crista supraoccipitalis along the midline of the skull. The apetura narium externa face anterodorsally. The orbits are large and face anterolaterally. In lateral view, the skull has a low profile relative to modern forms. Ventrally, a complete secondary palate is preserved. Skull roof (Prefrontal, Postorbital, Frontal, Parietal, Jugal)—The prefrontal borders the anterodorsal rim of the orbit and the posterior rim of the nares (if nasals are absent). It contacts the maxilla anterolaterally and the frontal posteromedially. Together, the prefrontals form a “V” with the open end posterior. The key shaped fissura ethmoidalis is visible anteriorly, and is dorsally and laterally bound by the prefrontal descending processes. Careful inspection indicates the presence of a suture near anterior rim of the prefrontals, but posterior to the dorsal edge of the nasal opening. Despite additional preparation of the underside of the nasal region, this “nasal suture” is only visible in dorsal view, making the presence or absence of nasals somewhat equivocal. The posterior rim of the apetura narium externa and the anterior rim of the prefrontals border the “nasals.” The frontals are pentagonal in shape and are bordered by the postorbital laterally, the parietal posteriorly, and prefrontals anterolaterally. The frontal is eliminated completely from orbital contact by the prefrontal and postorbital. In ventral view, the descending processes of the frontals form the lateral wall of the sulcus olfactorius. Although both postorbitals are damaged, the contact with the prefrontals, frontals, and parietals is visible. The postorbital forms the posterior rim of the orbit. The ventral contact with the jugal has been reconstructed on the right side. Ventrally, a transverse ridge extends posteromedially from the postorbital onto the parietal. Tong and Hirayama (2002) discuss this feature in Tasbacka Nessov 1987 and note that unlike Chelonia, the ventral postorbital ridge in Tasbacka is prominent and extends onto the parietal. The ridge in LACM 103351 is thick and appears to be similar to that described for Tasbacka (Tong and Hirayama 2002). Unfortunately, it is difficult to determine relative prominence from figures. With the exception of E. hutchisoni hutchisoni, Tasbacka, and Chelonia, this postorbital ridge is not described for other cheloniids sensu lato. Inspection of another modern cheloniid (Caretta, UCMP 119069) reveals that the postorbital ridge is weak, but still extends posteromedially into the parietal.

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At the parietal, however, it is more of a swelling, not a distinct ridge.

A

The parietal is almost entirely preserved. It is a broad, trapezoidal bone that contacts the frontal anteriorly and the postorbital laterally. Taken together, the parietals form the majority of the skull roof. Ventrally, the dorsal portion of the descending processes of the parietals is preserved. These processes extend along the entire length of the preserved parietals, contacting the supraoccipital posteriorly. Only the right jugal is preserved. It makes up the posteroventral rim of the orbit in lateral view. Sutures are not readily visible along the orbital wall, but the jugal undoubtedly contacts the maxilla and palatine. In lateral view, jugal contact with the postorbital is missing, but anteriorly it contacts the maxilla below the orbit. Basicranium (Supraoccipital, Exoccipital, Prootic, Opisthotic)—The basicranium of LACM 103351 is largely missing. The preserved portions entail the anterior portion of the supraoccipital and parts of the left exoccipital, prootic, and opisthotic. The preserved contacts of the supraoccipital include the parietals dorsally and the remaining elements lateroventrally. Most of the crista supraoccipitalis is not preserved. The ventral surface of the supraoccipital forms the posteromedial roof of the cavum cranii. This portion of the supraoccipital is smooth and U-shaped, formed by two venterolateral processes. On the left side, the venterolateral process articulates with the exoccipital, prootic, and opisthotic. These bones are missing on the right side, but the sutural connections are preserved,

1 cm

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A

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Fig. 2. Holotype cranium of Euclastes hutchisoni (LACM 103351). A. Dorsal view. B. Ventral View. C. Right lateral view. Visible sutures are highlighted. Abbreviations: c.l., cavum labyrinthicum; ex, exoccipital; fr, frontal; ju, jugal; mx, maxilla; n?, probable nasal; op, opisthotic; pa, parietal; pal, palatine; pmx, premaxilla; po, postorbital; pref pref, prefrontal; pro, prootic; sup, supraoccipital; vo, vomer.

B Fig. 3. Euclastes hutchisoni hutchisoni, LACM 103351, holotype, the feeding apparatus of. A. Detailed view of the palate. B. Detailed view of the dentary triturating surface.

LYNCH & PARHAM PARHAM—HARD-SHELLED SEA TURTLES as is the dorsal surface of the cavum labyrinthicum. The right exoccipital is damaged so that only its dorsal half is preserved. The contribution to the condylus occipitalis is present. Lateral to this is a hypoglossal nerve foramen, still filled with sediment. The suture between the exoccipital and the opisthotic is barely visible. The lateral process of the opisthotic (which contacts the jugal and squamosal) is present. The anteromedial surface of the opisthotic forms the posterolateral wall of the cavum labyrinthicum. Most of the prootic is preserved. Posteriorly, the prootic forms the anterior wall cavum labyrinthicum. In modern sea turtles the prootic has a swollen appearance and the anterolateral wall of the prootic is convex. In LACM 103351, the anterolateral wall of the prootic lacks this convexity. Laterally, the path of stapedio-temporale canal is visible. Palate (Premaxilla, Maxilla, Vomer, Palatine)—The holotype has a complete secondary palate and a relatively low tomial ridge (Fig. 3A). The triturating surface of the palate itself is mostly flat and heavily perforated by nutrient foramina. The ventrally exposed shape of the vomer is rectangular and of constant width throughout its length. The vomer broadly contacts the premaxillae anteriorly, the maxillae anterolaterally, and the palatines posterolaterally. The vomerine pillar and dorsal plate of the vomer extend just beyond the posterior edge of the ventral plate of the vomer. Consequently, the nares are visible in ventral view. It is possible that the posterior portion of the ventral plate of the vomer is damaged. We suspect this to be true because the area of

A

this shelf that forms the anterior rim of the apetura narium interna appears to have a rough, unnatural edge. In Euclastes gosseleti Tasbacka, Caretta, and Lepidochelys Fitzinger 1843, gosseleti, the posterior edge of the vomerine pillar is anterior to the posterior termination of the choanae (Zangerl 1971, 1980, Tong and Hirayama 2002). We cannot determine the condition for most other taxa, but it may have phylogenetic value. Nevertheless, E. hutchisoni differs from Euclastes gosseleti gosseleti, Tasbacka, Lepidochelys Lepidochelys, and Caretta, in which the undershelving of the nasal passages is more pronounced (Zangerl 1971, 1980, Tong and Hirayama 2002). Although the anterior rim of the apetura narium interna is apparently damaged in LACM 103351, it was probably positioned anterior to the anterior rim of the fossa temporale inferior. The premaxillae form the anterior rim of the apetura narium externa. In ventral view there may be a remnant suture between the premaxillae, but they are fused for the majority of their contact. Ventrally, the premaxillae are bordered by the maxillae laterally, and the vomer posteriorly. The ventral surfaces of the premaxillae and vomer are deeply incised with a groove that indicates the occlusal pattern of the keratinized beak that covered the dentary (Figs. 3, 4). The groove is anchor-shaped and the area between the arms and shaft have ventrally projecting processes. The maxilla is a large bone that, in lateral view, forms the anteroventral and anterior edge of the orbit. In lateral view, it contacts the jugal posteriorly, the premaxilla anteriorly, the prefrontal posterodorsally, and borders the apetura narium

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Fig. 4. Euclastes hutchisoni dentaries. A. LACM 103351, dorsal view. B. LACM 103351, left lateral view, the anterior suture of the surangular is highlighted. C. BVM 0810, dorsal view. D. BVM 0805, dorsal view.

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Fig. 5. Euclastes hutchisoni hutchisoni, BVM 0810, vertebrae. A. Eighth cervical, anterior view. B. First thoracic, ventral view.

externa laterally. On the orbital floor, the maxilla hosts a horizontally trending foramina orbitonasale. The maxilla presumably contacts the prefrontal, vomer, and jugal on the orbital floor, but the sutures are obscured. In ventral view, the maxilla contacts the premaxilla and vomer medially, and the palatine posteromedially. The maxilla forms the posterolateral margin of the secondary palate and a significant portion of the triturating surface of the palate. The palatine contacts the maxilla laterally, the vomer anteromedially, and forms the anterolateral rim of the apetura narium interna. The palatine is of constant width. It extends laterally from the posterior portion of the vomer and then projects posteriorly. Consequently, there is a distinct break in the slope of the palato-maxillary suture. The posterior-most edge of the palatines is damaged so the ultimate extent of the palatines is unknown. Dorsally, the anterior sutures of the palatines are not distinct, but they do contact the vomer anteromedially and the maxillae laterally. Mandible—The —The dentary is broad and flat (Fig. 4A). The — symphyseal length (3.8 cm) is 28.6% of the total mandible length (13.3 cm). The triturating surface is extensive, but the posterior edge does not reach a hypothetical line connecting the foramen dentofaciale majus on each side (Zangerl 1971). The width at the level of the dentofaciale foramen is 7.0 cm. Posteriorly, there is a sagittal swelling of the symphysis. A medial, triangular-shaped convexity divides the triturating surface into concave halves. There is no evidence of the keratinous beak that occluded with the incised palate. Posteromedially, the sulcus cartilaginis meckelii is present. The surangular does not extend anteriorly onto the dentary in lateral view (Fig. 4B). Description of BVM 0810 BVM 0810 is the most complete specimen of E. hutchisoni hutchisoni, comprising a mandible, a partial plastron, three cervical verte-

bra elements, four costals, a pygal, and seven peripherals. The dentary of BVM 0810 matches the morphology of LACM 103351. We recognize the problems that tenuous referrals may cause in the future and so urge future students to question our association. However, the unusually plesiomorphic characters in the postcrania of BVM 0810 (see below) is consistent with the unusually plesiomorphic characters of the type skull (see above). Dentary—The symphyseal convexity of BVM 0810 (Fig. 3D) is similar to that of the holotype. This convexity is despite the presumably younger age class, of BVM 0810 (1.8 cm symphysis length compared to 3.8 cm in the holotype). Vertebrae—BVM 0810 includes two vertebrae, an eighth cervical and a first thoracic (Fig. 5). These elements are typically cheloniid. The eight cervical is procoelous. The anterior facet is singular, a character shared by Ctenochelys and Argillochelys. The majority of cheloniids s.l., including all of the crown taxa, have a doubled articulation between the eighth and seventh cervicals. Plastron—BVM 0810 includes a partial right hypoplastron and two unidentifiable plastron fragments (Fig. 6A). No scale sulci are visible. The hypoplastron shows that, if whole, the plastron of BVM 0810 would be wider than long. This character is shared by Procolpochelys Hay 1908, a poorly known turtle from the Miocene of New Jersey and Maryland (Zangerl and Turnbull 1955, Weems 1974). Costal Elements—Four costal elements from the shell of BVM 0810 are present, all of which lack dorsal sculpturing (Fig. 6B). Additional specimens of unsculptured costals are housed in the collections of the UCMP. We do not refer these specimens to E. hutchisoni because unsculptured costals are widely distributed feature of Cheloniidae s.l. The rib heads of Euclastes hutchisoni are more pronounced and extend more ventrally than those of living cheloniids (Fig. 6C). Referred Isolated Specimens Nineteen isolated specimens are referred to Euclastes hutchisoni (three dentaries, 16 limb elements). Dentaries—In addition to the type specimen and BVM 0810, three dentaries from Sharktooth Hill bear a remarkable similarity to the type specimen: BVM 0806 (2.7 cm symphysis length), BVM 0805, a large specimen (6.0 cm symphysis length); UCMP 98202, a fragment. The primary morphological difference between these specimens is on the dorsal crushing surface. The largest jaw (BVM 0805; Fig. 4C) possesses a completely flat triturating surface, lacking the sagittal swelling seen on the holotype and other specimens. Humeri—Ten isolated humeri are referred to Euclastes hutchisoni on the basis of their unusually plesiomorphic morphology (see Referred Materials above). One entirely preserved humerus (UCMP 65617; Fig. 7B) is used to illustrate the humeral morphology of E. hutchisoni. All referred specimens match UCMP 65617 in general morphology. UCMP 65617 possesses a relatively narrow and cylindrical shaft viewed in dorsal and ventral aspect. The shaft is notice-

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C B Fig. 6. Euclastes hutchisoni hutchisoni, BVM 0810, shell pieces. A. Right hypoplastron, ventral view. B. Costal fragment, dorsal view. C. Different costal fragment, posterior view.

ably curved in lateral view and the distal articular surface of the humerus is reduced. While displaying the morphology of a marine turtle, the proximal end of the humerus is still less derived compared to those of living cheloniids. The medial process is elongated proximally, a character observed in sea turtles. But unlike living cheloniids s.l., the proximal extent of the medial process is subequal to the head in ventral view. The lateral process of UCMP 65617 also differs from those of modern cheloniids in its more proximal position. In Cheloniidae s.s. the process shifts further distally onto the shaft, giving the supracoracoideus muscle increased leverage. The lateral process of UCMP 65617 is shifted distally relative to the primitive condition, but its medial half is still adjacent to the intertubercular fossa. Therefore, like the early cheloniids Toxochelys and the Lophochelyinae Zangerl 1953, E. hutchisoni retains a level of locomotory specialization intermediate between the plesiomorphic non-pelagic condition and the derived condition of living sea turtles (Fig. 7). Femora—Six femora are referred to Euclastes hutchisoni based on their unusually plesiomorphic morphology (see

Referred Materials above). BVM 0471 (Fig. 8) is used to demonstrate the morphology seen in all referred femora. The shaft is narrow and laterally curved. The head is round and extends further anteriorly than the trochanters. The trochanters are separated by a deep fossa. In cheloniids s.s., a ridge connects the femoral trochanters. PHYLOGENETIC ANALYSIS In order to test the phylogenetic position of Euclastes hutchisoni, we performed a cladistic analysis of 31 osteological hutchisoni characters for 13 of the better-known cheloniids s.l. (Table 1). Our analysis is based on Parham and Fastovsky (1997). That data set included 24 characters and 13 taxa. For both studies, included taxa are restricted to those known from skull, shell, and limb material. We do not include the Hornerstown Euclastes (known only from skull material), but add Euclastes hutchisoni. Toxochelys and Ctenochelys are designated as outgroups. In our matrix, character #13 of Parham and Fastovsky (1997) is divided into two characters. The exclusion of the Hornerstown Euclastes renders two other characters

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A

A

B

Fig. 8. Euclastes hutchisoni hutchisoni, BVM 0471, right femur. A. Anterior view. B. Ventral view.

B

C Fig. 7. Cheloniid Cheloniid s.l. turtles, left humeri in dorsal, ventral, and lateral views. A. Ctenochelys sp., CNHM PR 27334. B. Euclastes hutchisoni, UCMP 65617. C. Chelonia, UCMP 186567. hutchisoni

from Parham and Fastovsky (1997), #5 and #7, phylogenetically uninformative. Additional alterations to the matrix are noted with each character where necessary. The data were analyzed using the parsimony algorithm of PAUP* 4.0b3a (Swofford 1998). Character List The distribution of the following 31 characters for 13 cheloniid s.l. taxa (incl. E. hutchisoni) can be found in Table 1.

Cranial 1. Secondary palate: (0) present; (1) absent (=Parham and Fastovsky 1997: #1). Originally, this character had three character states: (0) absent; (1) present; (2) extensive. This character has been modified to recognize the simple presence or absence of a secondary palate. 2. Foramen palatinum posterius: (0) wide; (1) lost (=Parham and Fastovsky 1997: #2). 3. Contact of vomer with premaxillae: (0) broad; (1) reduced (=Parham and Fastovsky 1997: #3). Parham and Fastovsky (1997) state that all cheloniids s.s., except Natator McCulloch 1908, have a reduced contact between the premaxillae and the vomer. However, Natator was incorrectly coded as having the derived state in their matrix. 4. Foramen caroticum laterale much larger than foramen anteris canalis caroticus interni: (0) absent; (1) present (=Parham and Fastovsky 1997: #4). 5. Dentary: (0) flat triturating surface; (1) lingual ridges present; (2) ridge along entire length of symphysis (=Parham and Fastovsky 1997: #6). 6. Tomial ridge: (0) pronounced; (1) low (=Parham and Fastovsky 1997: #7). 7. Surangular extending anteriorly into dentary: (0) absent; (1) present. (=Parham and Fastovsky 1997: #8). 8. Shape of the anterior portion of the vomer: (0) constant width; (1) variable width (=Parham and Fastovsky: 1997: #9). 9. Prefrontal scutes: (0) one pair; (1) two pair (=Parham and Fastovsky 1997: #10).

0 0 0 — — 1 1 0 0 0 0 0 0 0 0 0 — 1 0 0 1 1 1 0 0 0 0 0 0 — 0 0 0 2 2 2 1 2 2 0 0 0 — 0 0 0 0 0 0 0 1 1 0 0 0 — 0 0 0 0 0 0 0 1 1 0 0 0 — 1 1 1 1 1 1 1 1 1 0 1 1 — — 1 1 2 2 2 2 2 2 0 0 0 0 1 1 1 1 1 1 1 1 1 1 0 — 0 0 — 1 1 1 1 1 1 1 0 0 — — 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 1 1 1 1 1 1 0 0 — — — 1 — — 1 1 1 1 1 0 0 — — 0 0 1 1 1 1 1 1 1 0 0 0 — 1 1 1 1 1 1 0 0 0 0 0 0 0 — 0 0 1 1 1 1 1 1 0 0 0 0 — 0 0 0 0 0 1 1 1 0 0 0 — 0 — 0 1 1 1 1 1 1 0 0 0 — 0 0 0 1 1 1 1 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 2 0 0 0 2 1 0 0 0 1 1 1 1 1 1 1 1 1 1 1 0 0 1 — 0 0 1 — 0 1 1 1 1 — — 0 — 0 0 0 — 0 0 1 1 1 0 0 1 0 0 1 1 — 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 2 0 0 2 1 2 1 0 0 0 0 1 — 1 0 1 1 1 1 1 1 1 0 0 0 0 0 0 0 — 0 1 1 1 1 0 0 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1 1 0 1 1 1 1 1 1 1 Toxochelys Ctenochelys Euclastes gosseleti Euclastes hutchisoni Argillochelys Eochelone Puppigerus Syllomus Natator Chelonia Eretmochelys Caretta Lepidochelys

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 8 7 6 5 4 3 2 1

Table 1. Data matrix for 31 osteological characters for 13 of the better-known cheloniids s.l. modified from Prham and Fastovsky (1997).

LYNCH & PARHAM PARHAM—HARD-SHELLED SEA TURTLES

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10. Process pterygoideus externus: (0) large; (1) reduced. The process pterygoideus externus is completely lost within the Dermochelyidae and the protostegid Archelon Wieland 1896 (Hirayama 1994). Within Cheloniidae s.l., this process is still present, but reduced in derived forms. Natator is the only living hard-shelled sea turtle in which the process pterygoideus externus is large (Zangerl et al. 1988). 11. Direction of the orbits: (0) dorsolaterally facing; (1) laterally facing. The direction of the orbits mainly differs among the durophagous cheloniids. The orbits of Euclastes gosseleti Euclastes hutchisoni gosseleti, hutchisoni, Tasbacka and modern durophagous cheloniids face laterally (Zangerl 1971, Zug 2001, Tong and Hirayama 2002). Euclastes platyops and the Hornerstown Euclastes retain the primitive condition (Hay 1908, Fastovsky 1985). 12. Skull shape: (0): Moderate width; (1) Broad; (2) Narrow and elongate. Skull shape is undoubtedly correlated to diet. For Euclastes and the carettines, a broad skull is associated with flat dentaries, a specialization for a durophagous diet. 13. Fused premaxillae: (0) absent; (1) present. Originally autapomorphic for Euclastes gosseleti (Zangerl 1971), the fused premaxillae are now a synapomorphy for E. gosseleti and E. hutchisoni. Non-Shell Post Cranial 14. Dorsal process of scapula forming relatively wide angle with acromion: (0) absent; (1) present (=Parham and Fastovsky 1997: #11). 15. Metischial processes: (0) pronounced; (1) reduced. (=Parham and Fastovsky 1997: #12). 16. Femoral trochanters: (0) separated by a fossa; (1) fossa obliterated (=Parham and Fastovsky 1997: #13 in part). We divide the femoral trochanters into two characters. 17. Femoral trochanter ridge: (0) not complete; (1) complete, without a notch (=Parham and Fastovsky 1997: #13 in part). 18. Tibial pit for pubotibialis and flexor tibialis internus muscles: (0) absent; (1) present (=Parham and Fastovsky 1997: #15). 19. Centra of the seventh cervical vertebra: (0) procoelous; (1) platycoelous (=Parham and Fastovsky 1997: #16). 20. Articulations of first and second digits: (0) movable; (1) immovable (=Parham and Fastovsky 1997: #17). 21. Humerus with V-shaped or triangular lateral process: (0) absent; (1) present (=Parham and Fastovsky 1997: #18). This character is modified from Parham and Fastovsky (1997) so that the derived morphology is restricted to Syllomus and the crown. Argillochelys, Argillochelys Eochelone, and Puppigerus do not possess the more distal and triangular lateral process. 22. Coracoid length in relation to humerus: (0) shorter; (1) longer (=Parham and Fastovsky #19). 23. Seventh to eighth centrum articulation of the cervical vertebra: (0) single; (1) doubled. The primitive condition for cheloniids s.l. is a single anterior facet of the seventh

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cervical vertebra (Hirayama 1994). The primitive character state is present in Ctenochelys, Ctenochelys Argillochelys, and Euclastes hutchisoni. Shell 24. Elongated plastron with a broad bridge: (0) absent; (1) present (=Parham and Fastovsky 1997: #20). 25. Rib-free peripherals: (0) only anterior and posterior to ribs; (1) between seventh and eighth ribs; (2) between sixth and seventh ribs (unordered) (=Parham and Fastovsky 1997: #21). Syllomus has the derived state (2). 26. Post nuchal fontanelles: (0) present; (1) absent (=Parham and Fastovsky 1997: #22). 27. Additional peripherals (0) absent; (1) present (=Parham and Fastovsky 1997: #23). The primitive condition for hard-shelled sea turtles is to have eleven peripherals on each side. 28. Additional pleural scales: (0) absent; (1) present. Primitive cheloniid s.l. taxa have four pleural scales on each side of the shell. Caretta caretta and Lepidochelys have at least five pleural scales per side (Parham and Fastovsky 1997), and Lepidochelys can have upwards to eleven (Deraniyagala 1939). The fossil carettine, Procolpochelys Procolpochelys, retains the primitive condition (Zangerl and Turnbull 1955). 29. Neurals (0) between eight and nine; (1) usually ten; (2) variable between extensive neural fragmentation and neural reduction. Fragmentation of the neurals is a common phenomenon among cheloniids, though the degree of fragmentation varies. Toxochelys Ctenochelys, Ctenochelys Puppigerus, Puppigerus Argillochelys, and Eochelone (Zangerl 1953, Moody 1974) Argillochelys primitively possess eight or nine neurals. Chelonia and Eretmochelys Fitzinger 1843 usually have ten (Deraniyagala 1939). Syllomus Procolpochelys, Syllomus, Procolpochelys Natator Natator, and Lepidochelys possess at least eleven neurals (Deraniyagala 1939, Zangerl and Turnbull 1955, Weems 1974, Zangerl et al. 1988). Lepidochelys can have 12 to 15 neurals, while Caretta is polymorphic and can exhibit fragmentation or reduction of neurals (Deraniyagala 1939). Natator can have up to 12 neurals (Zangerl et al. 1988). 30. Textured carapace elements: (0) absent; (1) present. Zangerl et al. (1988) describes an “irregular vermiculation” on the carapace elements of Natator. Natator, Natator Syllomus Syllomus, and Argillochelys share this character. 31. Shape of pygal: (0) notched posteriorly; (1) not notched (=Parham and Fastovsky 1997: #24). Upon revisiting this character, it was noticed that the pygal is not notched posteriorly for Euclastes gosseleti gosseleti, and it is truly unknown as to whether or not Argillochelys has a notched pygal. Additionally, Puppigerus was incorrectly coded in Parham and Fastovsky (1997) as having the primitive condition. DISCUSSION The results of our cladistic analysis are 10 equally parsimonious trees (53 steps, CI=.66). Figure 9 shows the strict consensus of these trees plotted against the stratigraphic occurrences of included taxa. The major differences between the

Fig. 9. A summary of 10 equally parsimonious trees discovered by phylogenetic analysis. The numbers on either side of the branch correspond to decay indices/bootstrap values (1000 replicates) respectively. Taxa are stem based (semi-circle), node based (open circle).

hypothesis presented here and that presented by Parham and Fastovsky (1997) are in the relationships of the crown group. In our analysis, four of the 10 most parsimonious trees place Syllomus as the sister taxon to Natator Natator, a hypothesis favored by Hirayama (1994). In five of our trees, Chelonia and Eretmochelys are sister taxa, a hypothesis not supported by molecular data (Dutton et al. 1996). In all trees, Euclastes hutchisoni is the sister taxon of Euclastes gosseleti and not near the crown. The relatively basal position of Euclastes within Cheloniidae s.l. is based on the absence of derived features. Plesiomorphic characters retained by Euclastes hutchisoni (and other Euclastes where known) include a wider than long plastron, a Toxochelys Toxochelys-like humerus, femoral trochanters separated by a deep fossa, a broad sutural contact between the vomer and premaxillae on the palatal surface, and a single facet on the anterior end of the eighth cervical vertebra. These characters leave little doubt that despite its young age, E. hutchisoni is not closely related to the crown (Cheloniidae s.s.).

LYNCH & PARHAM PARHAM—HARD-SHELLED SEA TURTLES Because it is known from both cranial and postcranial remains, Euclastes hutchisoni is one of the better-known species of Euclastes. Two other Euclastes have postcranial elements preserved: (1) the well-preserved skeletons of E. gosseleti from late Paleocene of Belgium; (2) a highly gyspumized specimen of Euclastes sp. from the Late Cretaceous Moreno Formation (Foster 1980). In all three instances, the postcrania of Euclastes conform to a level of specialization intermediate between the earliest cheloniids s.l. (e.g., Toxochelys) and modern Cheloniidae. The young age of E. hutchisoni makes the possible presence of nasals unexpected. Prior to the tentative recognition of these elements in Euclastes hutchisoni hutchisoni, they were restricted to the basal-most lineages within cheloniids s.l. (Toxochelys and the Lophochelyinae Zangerl 1953). Nasals are certainly absent in the oldest described specimens of Euclastes (Fastovsky 1985). The Miocene turtle fauna of Sharktooth Hill can be compared to a coeval assemblage from the Atlantic Coast, the Calvert Cliffs of Maryland (both are Barstovian). That fauna includes three species, “Psephophorus” Psephophorus calvertensis, Psephophorus” calvertensis Procolpochelys grandaeva Leidy 1851, and Syllomus aegyptiacus. A dermochelyid close to (potentially conspecific with) “P.” P P.” calvertensis exists in Sharktooth Hill, but direct comparisons are lacking. Syllomus aegyptiacus is widespread in Miocene oceans, also recorded from Asia (Shikama 1956) and Africa (Lydekker 1889b), and so its probable appearance at Sharktooth Hill is not surprising. However, we emphasize that the sole specimen of a Syllomus Syllomus-like turtle from California may be a different taxon of sculptured cheloniid s.l.. The reciprocal absence of Procolpochelys and Euclastes indicates a difference between the two faunas. Procolpochelys is hypothesized to be a basal carettine (Zangerl and Turnbull 1955), perhaps the oldest known member of the crown. On the other hand, Euclastes hutchisoni is the last vestige of a Cretaceous-Paleocene radiation of basal stem cheloniids. The total range of Euclastes specimens is Late Cretaceous to the middle Miocene, over 50 million years. The vast majority of Euclastes specimens date to the first ten million years of this interval (Late Cretaceous to late Paleocene). Post-Paleocene Euclastes are restricted to two far flung occurrences: E. hutchisoni and E. planimenta (Owen 1842). The latter is known from a single skull from the early Eocene London Clay. The decline of Euclastes is concomitant with the increased occurrence of more crownward forms, most of which are too fragmentary to include in cladistic analyses (see Weems 1988; Lapparent de Broin 2001). The last appearance of Euclastes is coeval with the first appearance of Procolpochelys and Syllomus, both of which are hypothesized to be the oldest members of the crown. Continued research into the morphology and phylogenetics of Cenozoic marine turtles will undoubtedly shed more light on the modernization of sea turtle faunas.

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ACKNOWLEDGMENTS We would like to start by thanking Bob Ernst for access to specimens at the Buena Vista Museum and for his noble efforts to preserve the fossils from Sharktooth Hill. SCL especially thanks Eduardo Avelar and her family, who provided invaluable support and encouragement throughout the course of this project. SCL also thanks her mentors Joe Medeiros, Tricia Maloney, Jenny Davidson, and Karen Haubensak. Kevin Padian of the UCMP is thanked for his unwavering support of turtle research and helpful comments. Pat Holroyd was instrumental in helping both authors study materials at the UCMP, and along with Nick Pyenson and Thomas Stidham, took part in the 2002 “expedition” to Sharktooth Hill. Fellow chelonologists Ted Papenfuss, Chris Feldman, and Thomas Stidham aided JFP in previous visits to the BVM. Mike Metz facilitated some of those early visits. Sam Mcleod helped arrange for the loan of the holotype to Kevin Padian so that it could be studied by the authors, and also allowed Jane Mason to skillfully uncover more of the nasal region. JFP would like to thank Carl Gillies, Kevin Moniz, and the Parham family. During the course of this study, JFP was funded by the University of California Museum of Paleontology, a National Science Foundation Graduate Fellowship, a University of California Vice Chancellor’s Graduate Fellowship, an Annie Alexander Fellowship, and grants from the Sam and Delores Welles fund and Sigma Xi (National Chapter). This is UCMP Contribution #1801. LITERATURE CITED Averianov, A.O., and A.A. Yarkov. 2000. Some turtle remains from the Cretaceous and Paleogene of Volgograd region, Russia. Russian Journal of Herpetology 7(2):161–166. Barnes, L.G. 1976. Outline of eastern North Pacific fossil cetacean assemblages. Systematic Zoology 25(4):321–343. Barnes, L.G. 1978. A review of Lophocetus and Liolithax and their relationships to the delphinoid family Kentriodntidae (Cetacea: Odonotoceti). Natural History Museum of Los Angeles County Science Bulletin 28:1–35. Barnes, L.G., and E. Mitchell. 1984. Kentriodon obscurus (Kellogg, 1931), a fossil dolphin (Mammalia: Kentriodontidae) from the Miocene Sharktooth Hill bonebed in California. Contributions in Sciences of the Los Angeles County Museum 353:1–23. Batsch, A.J.G.C. 1788. Versuch einer Anleitung, zur Kenntniß und Geschichte der Thiere und Mineralien. I. Akademische Buchhandlung, Jena. 528 pp. Berggren, W., and J.A. Van Couvering. 1974. The late Neogene. Biostratigraphy, geochronology and paleoclimatology of the last 15 million years in marine and continental sequences. Palaeogeography, Palaeoclimatology, and Palaeoecology 16(1/2): i–xi, 1–216. Berry, C.T., and W.G. Lynn. 1936. A new turtle, Peritresius virginianus, from the Miocene of Virginia. Proceedings of the American ianus Philosophical Society 76(2):175–190. Bonaparte, C.L. 1832. Saggio d’una distribuzione metodica degli animali vertebrati a sangue freddo. Antonio Boulzaler, Roma.

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Repenning, C.A., and R.H. Tedford. 1977. Otariid seals of the Neogene. United States Geological Survey Professional paper 992: I–vi, 1–93, xxiv pls. Rowe, T., and J. Gauthier. 1992. Ancestry, paleontology, and definition of the name Mammalia. Systematic Zoology 41(3): 372–378. Seeley, H.G. 1871. Note on some chelonian remains from the London Clay. Annual Magazine of Natural History 8:234–237. Shikama, T. 1956. Miocene Chelonia of Japan. Science Reports of the Yokohama National University. Section II Biological and Geological Sciences 5:43–62, III–VIII pl. Staesche, K. 1929. Schildkrötenreste aus der oberen kreide patagoniens. Palaeontographica 72:103–123. Staron, R.M., B.S. Gradnstaff, W.B. Gallagher, and D.E. Grandstaff. 2001. REE signatures in vertebrate fossils from Sewell, NJ: Implications for location of the K-T boundary. Palaios 16: 255–265. Sukhanov, V.B. 2000. Mesozoic turtles of Middle and Central Asia. pp. 309–367. in M.J. Benton, M.A. Shishkin, D.M. Unwin, and E.N. Kurochkin (eds.). The Age of Dinosaurs in Russia and Mongolia. Cambridge University Press, United Kingdom. Swofford, D.L. 1998. PAUP*: Phylogenetic analysis using parsimony (*and other methods) version 4.0b3a. Sinauer Associates Inc., Sunderland. Tong H., and R. Hirayama. 2002. A new species of Tasbacka (Testudines: Cryptodira: Cheloniidae) from the Paleocene of the Ouled Abdoun phosphate basin, Morocco. Neues Jahrbuch für Geologie und Paläontologie 5:277–294. Weems, R.E. 1974. Middle Miocene sea turtles (Syllomus, Syllomus ProcolSyllomus, pochelys Psephophorus) from the Calvert Formation. Journal of pochelys, Paleontology 48(2):278–303. Weems, R.E. 1980. Syllomus aegyptiacus aegyptiacus, a Miocene pseudodont sea turtle. Copeia 1980(4):621–625. Weems, R.E. 1988. Paleocene turtles from the Aquia and Brightseat Formations with a discussion on their bearing on sea turtle evolution and phylogeny. Proceedings of the Biological Society of Washington 101:109–145. Wieland, G.R. 1896. Archelon ischyros ischyros, a new gigantic cryptodire testudinate from the Fort Pierre Cretaceous of South Dakota. American Journal of Science 2(4):399–412. Wieland, G.R. 1904. Structure of the Upper Cretaceous turtles of New Jersey: Lytoloma. American Journal of Science XVIII: 183–196, pl.V–VIII. Zangerl, R. 1953. The vertebrate fauna of the Selma Formation of Alabama. Part IV. The turtles of the family Toxochelyidae. Fieldiana: Geology Memoirs 3:135–277. Zangerl, R. 1971. Two toxochelyid sea turtles from the Landenian sands of Erquelinnes Hainaut of Belgium. Institut Royal des Sciences Naturelles de Belgique Mémoires 169:1–32. Zangerl, R. 1980. Patterns of phylogenetic differentiation in the toxochelyid and cheloniid sea turtles. American Zoologist 20: 585–596. Zangerl, R., L.P. Hendrickson, and J.R. Hendrickson. 1988. A redescription of the Australian flatback sea turtle, Natator depressus. Bishop Museum Bulletin in Zool Zoology 1:1–69.

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Fig. 10. Distribution of Euclastes (see Appendix 1).

Zangerl, R., and W.D. Turnbull. 1955. Procolpochelys grandaeva (Leidy), an early carettine sea turtle. Fieldiana: Zoology 37: 345–382. Zug, G.R. 2001. Turtles of the Lee Creek mine (Pliocene: North Carolina). Smithsonian Contributions to Paleobiology 90: 203–218

APPENDIX I The following is a review of 12 previously published records of Euclastes listed in three stratigraphic bins (Cretaceous, Paleocene, Eocene), in order of publication respectively. All of these records are represented in Fig. 10. “Euclastes” Euclastes melii Misuri 1910 from the Miocene of Italy is Euclastes” considered to be a carettine (Zangerl and Turnbull 1955, Weems, 1974) and therefore excluded. De Lapparent de Broin (2000) records the presence of other Euclastes-like Euclastes taxa in the Paleogene phosphates of Morocco and Tunisia, but claims that “Euclastes” Euclastes douvillei De Stefano 1902 from Euclastes” the Eocene of Tunisia is not one of them. On the other hand, “Thalassochelys” Thalassochelys phosphatica De Stefano 1903, from Thalassochelys” the same formation, may be a Euclastes. Cretaceous Hornerstown Euclastes Wieland (1904). Age—Late Cretaceous (Maastrichtian; see Staron et al., 2001). Locality—Hornerstown Formation, New Jersey, USA. Comments—This turtle includes all of the skull material formerly referred to Osteopygis emarginatus. Moreno Euclastes Foster (1980). Age—Late Cretaceous. Locality—Moreno Formation, California, USA. Comments—“Osteopygis sp.” of Foster (1980).

Quiriquina Euclastes Gasparini and Biro-Bagoczky (1986). Age—Late Cretaceous (Maastrichtian). Locality—Quiriquina Formation, Lirquén Province, Chile. Comments—“Osteopygis Osteopygis sp.” of Gasparini and Biro-Bagoczky (1986) and “Osteopygis Osteopygis aff. sculptus sculptus” of Karl et al. (1998). The type specimen of Osteopy Osteopygis sculptus Staesche 1929 is a pleurodire (de Broin and de la Fuente 1993). Euclastes priscus (Karl, Tichy, and Ruschak 1998). Age— Late Cretaceous (Maastrichtian). Locality—Phosphates of Morocco, Northwest Africa. Type specimen—IGPS No. 590, a skull. Comments—“Osteopygoides Osteopygoides priscus priscus” of Karl et al. (1998). Paleocene Euclastes platyops Cope 1867. Age—Late Paleocene. Locality—Vincentown Formation, Hurffsille, New Jersey, USA. Type specimen—ANSP 10187, a skull. Comments—Euclastes platyops is the type species of Euclastes. Hay (1908) thought that the genus Euclastes was preoccupied and so erected a new genus, Rhetechelys. We are unable to find an additional usage of Euclastes anywhere and so follow Kuhn (1964) and de la Fuente and Casadío (2000) in considering Euclastes as the valid genus name for E. platyops. Euclastes gosseleti (Dollo 1886). Age—Late Paleocene. Locality—Erquelinne Sands, Belgium. Type specimen— I.R.Sc.N.B. No. 1563, a nearly complete carapace, partial plastron, good skull and mandible, part of the tail, and part of the pelvis. Comments—This species was originally placed in the genus Pachyrhynchus Dollo 1886, a name preoccupied by a curculionid beetle (Pachyrhynchus Germar 1824). The next year Dollo (1887) transferred the species to the genus

LYNCH & PARHAM PARHAM—HARD-SHELLED SEA TURTLES Erquelinnesia, and then a year later (Dollo 1888) to Euclastes, Euclastes the combination employed here. Brightseat Euclastes Weems (1988). Age—Early Paleocene. Locality—Brightseat Formation, Maryland, USA. Comments—“Osteopygis Osteopygis emarginatus emarginatus” of Weems (1988). Euclastes roundsi Weems (1988) Age—Late Paleocene (Thanetian). Locality—Piscataway Member of the Aquia Formation, Virginia, USA. Type specimen—USNM 412108, a partially preserved skull, with only the ventral surface readily visible. Comments—This turtle was originally called Osteopygis roundsi by Weems (1988) who also refers additional material to this taxon including a costal fragment (USNM 9357), isolated plastral elements (USNM 357710), and carapace fragments associated with a skull (USNM 357713). These referrals are considered invalid based on insufficient evidence. The type specimen is a skull and so therefore no postcrania can be confidently referred to E. roundsi. The referred skull specimen, USNM 357713, is too poorly preserved to be referred to E. roundsi with confidence. Euclastes meridionalis (de la Fuente and Casadío 2000) Age—Early Paleocene. Locality—Roca Formation, Cerros Bayos, La Pampa Province, Argentina. Type specimen—GHUNLPam 19137, a posteromedial skull fragment. Comments—This taxon was originally placed in its own genus

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Pampaemys de la Fuente and Casadío 2000. Karpovka Euclastes Averianov and Yarkov (2000). Age—Late Paleocene. Locality—Karpovka Formation, Volgograd Region, Russia. Comments—“Osteopyginae indet.” of Averianov and Yarkov (2000). Oued Zem Euclastes de Lapparent de Broin (2000). Age—Late Paleocene to Early Eocene. Locality—Ouled Abdoun Basin. Comments—According to de Lapparent de Broin (2000), the skulls of these undescribed turtles (“Osteopygidae indet.”) are often sold attached to the shells of the pleurodire Taphrosphys Cope 1869. Eocene Euclastes planimenta (Owen 1842). Age—Early Eocene. Locality—London Clay, Harwich region, United Kingdom. Type specimen—S.M.C. 20419, a skull with jaw attached. Comments—This turtle is the type species of Glossochelys Seeley 1871. Miocene Euclastes hutchisoni Lynch and Parham 2003. Age— Middle Miocene. Locality—Sharktooth Hill, Kern County, California, USA. Type specimen—103351, a skull and jaw.