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Paludicola 5(3):92-106 November 2005  by the Rochester Institute of

REDESCRIPTION OF PLATYURUS COPE 1868 (: ) FROM THE UPPER (LOWER ) OF , U.S.A.

Sven Sachs

Institut für Paläontologie, Freie Universität Berlin, Haus D, Malteser Strasse 74-100, 12249 Berlin, [email protected]

ABSTRACT The specimen of Elasmosaurus platyurus Cope, 1868 from the Upper Cretaceous (lower Campanian) of Kansas, U.S.A. is redescribed. It consists of part of the (e. g., both premaxillae, parts of the maxillae, the occipital condyle and parts of the dentaries), the almost complete , including the - complex, as well as the pectoral and pelvic girdles (although the latter are now lost). The Elasmosaurus can be defined by two unambiguous autapomorphies, the presence of six premaxillary teeth and the high number of 71 . It also exhibits a number of advanced features, which are discussed and compared with other elasmosaurs.

INTRODUCTION Carpenter (1999). In the present paper the type specimen of Elasmosaurus platyurus (ANSP 10081) is Elasmosaurus platyurus is the first described and redescribed and the diagnostic features are pointed out nominal genus of the Elasmosauridae, a family of long in order to state the taxonomic position of the genus necked plesiosaurs recorded from the Lower to within the Elasmosauridae. the Upper Cretaceous. In 1867 a military physician Dr. Institutional abbreviation: ANSP: Academy of Theophilus H. Turner discovered the first remains of Natural Sciences in Philadelphia. the type specimen, two fragments of vertebrae, in a ravine, approximately 23 km northeast of Fort Wallace in western Kansas. In the same , Dr. John W. Le Conte brought the specimens to the Academy of SYSTEMATIC PALAEONTOLOGY Natural Sciences in Philadelphia, where examined them (Almy, 1987). Cope Order PLESIOSAURIA de Blainville, 1835 recognized that they were from a plesiosaur and Superfamily Welles, 1943 noticed the importance as being part of a then barely Family ELASMOSAURIDAE Cope, 1869 represented group of in the New World. The remaining parts of the skeleton were excavated ELASMOSAURUS PLATYURUS Cope, 1868 and brought to Philadelphia with support by the Academy in early 1868. Later Cope more fully Diagnosis—Premaxillae bear six teeth per side; described the specimen in a preprint of the final paper. atlas-axis complex long and low, with distinct sagittal In his first attempt of a reconstruction Cope keel on ventral side; total number of cervical vertebrae erroneously placed the head at the end of the tail. After 71; mid-cervicals anteroposteriorly elongate; feature- realizing this mistake all copies of the preprint were complex of 4 sacral vertebrae and prominent midline recalled and were then reprinted with a new bar in pectoral and pelvic girdles. reconstruction (Storrs, 1984; for further historic Material—ANSP 10081, incomplete skeleton, information, also see Almy, 1987, and Davidson, 1997, comprising both premaxillae, part of the posterior 2002). section of the right , 2 maxillary fragments with Although Elasmosaurus platyurus is the first teeth, anterior portions of dentaries, three additional described member of the Elasmosauridae, a detailed fragments, 2 indeterminable cranial fragments, 72 description, including all parts of the type specimen has cervical vertebrae, including the atlas-axis complex, 3 only been provided by Cope (1869, 1875). Additional pectoral, 6 dorsal, 4 sacral and 18 caudal vertebrae, as studies, mainly on the postcranium, have been well as a number of rib fragments. Pectoral and pelvic undertaken by Welles (1952), Storrs (1999) and girdles originally preserved, but now missing. 92 SACHS--REDESCRIPTION OF ELASMOSAURUS PLATYURUS 93

Measurements of cranial elements are given in Table 1; jaw, thus they are determined as fragments of the those of vertebrae in Table 2. maxillary. Locality and Horizon—Near McAllaster, Logan Occipital Condyle—The hemispherical occipital Country, Kansas. Sharon Springs Shale Member, Pierre condyle is present and still articulates with the atlas Shale (lower Campanian) (for more information see centrum (Figure 4A, B), thus no further observations Storrs, 1999:3-4). were possible. —The present anterior portions of the DESCRIPTION dentaries are well preserved and still bear parts of the teeth in all alveoli (Fig. 1C, D). Five teeth are present Cranium per side, which are all developed as large fangs and appear to be about equal in diameter as indicated by Premaxilla—Both premaxillae (Figure 1 A, B) their cross sections. The symphysis is well ossified so are almost completely preserved and well co-ossified, that no suture is visible between the rami, and extends as no medial suture is visible. They fit well together to the level of dentary four. Dorsally, in about the with the dentary portions, but show clear traces of posterior half of the symphyseal margin, a prominent dorsoventral crushing. Dorsally, along the midline, a triangular shaped bulge is formed. From here, at the low keel is present (Figure 2) that might have been point where the rami are separated, two medially more distinct before the skull was compressed. situated, elongate, thickened structures are formed that Anteriorly the tip of the snout is well-rounded and follow the rami posteriorly. almost semicircular in dorsal view. The ventral sides of Additional Jaw Fragments—Among the jaw the premaxillae are not well preserved. Medially, fragments are three other tooth bearing elements that behind the alveolar part, the vomeronasal fenestrum is cannot be referred to the maxillary or the dentary with visible as a broad triangular depression (Figure 2). certainty. One of them (here called fragment D, Figure Cope (1868:53) stated that eight teeth are present 3D) bears two large alveoli which served strong fang- in each premaxilla. This statement cannot be like teeth as they are usually present in the anterior half confirmed. Indicators for tooth positions are of the dentary. The other two (here called fragment E, concavities in the lingual edges of the alveolar parts Figure 3E and fragment F, Figure 3F) have (Figure 2). Six of these concavities are present on each comparatively small alveoli, which indicates that were side. Comparing the specimen with the premaxillae of situated in the posterior half of the jaw. other elasmosaurs and considering the fact that a suture Additional Cranial Material—Among the to the maxillae is not visible, it can be concluded that numerous indeterminable fragments are two pieces, the fragment represents the premaxillae only. The which probably belong into the cranium. One (here premaxillary-maxillary contact would most probably called fragment G, Figure 3G, H) has a robust have been immediately behind the last concavity, thus appearance and bears a pan-like structure that could a total number of six teeth per premaxilla is most have served for articulation. On one side, this structure parsimonious. Only fragments of the second and third is bordered by a blunt, broad process. Its general tooth are preserved in the right premaxilla, being appearance is similar to the articular, in which the pan- formed as large fangs. The first premaxillary teeth, of like structure would be part of the , which only cross-sections are present, are clearly however the preservation is to poor to provide an smaller than the succeeding ones and are located unambiguous determination. Another possible between the first two teeth of the dentaries. The apex of interpretation is that the element represents a fragment what appears to be a replacement tooth, is visible in the of the right squamosal with part of the right articular second alveolus of the left premaxillary. A fragment of fused onto its inner surface. Figure 3G would then the sixth tooth of the right premaxilla is attached to the show the inner surface of the eroded or broken off right lower jaw as can be seen when reassembling the . quadrate. The blunt process then could be the temporal Maxilla—One fragment (Figure 3A) apparently arch process of the squamosal. The other fragment is represents part of the posteriormost section of the right curved and has one flat side (here called fragment H, maxillary. Its medial side is formed as a strong Figure 3I). Again, a clear determination is not possible, dorsolaterally curved wall, while the lateral side is less because of the poor preservation. Eventually it could curved and not as strong. The fragment bears some have been part of the skull roof (e.g. the frontal). alveoli of which only four are clearly visible. They are very small, compared with the other tooth-bearing Vertebral Column fragments. Among the latter are two (here called fragment B and C) that are lateromedially flattened, Atlas-axis Complex—The atlas-axis complex is bearing one large tooth each (Figure 3B, C). Their almost completely preserved. Only the cervical ribs general appearance would be unusual for the lower and the most posterodorsal section of the neural spine are missing. It is horizontally rectangular in outline in

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TABLE 1. Measurements (in cm) of the cranial elements of ANSP 10081. ______

lateral view (Figure 4A-C). Although both centra are neural canal is clearly higher. On the preserved right well co-ossified, a suture-like structure is visible at the side a moderately large circular foramen is present. It is right lateral side. However, this structure might be an situated at the base of the neural arches, between the artefact, due to lateral pressure onto the centrum. The posterior edge of the neural arch of the atlas and the co- indicates that the specimen was an adult anterior side of the neural arch of the axis. individual. The neural spine is incompletely preserved, as the The neural arches are well preserved on the right posterior half of the axis section is missing. It is very side of the complex and are broken off on the left. low and posterodorsally oriented at an angle of Sutures between the centra and neural arches are not approximately eight degrees to the horizontal plane. visible. Interestingly, the neural arches are The centra of the atlas and axis are about extraordinarily thin and relatively high. Thus the neural equal in length, each having a quadrate shape in lateral canal has a high triangular outline in posterior view. view. The axis centrum shows prominent depressions The ventral section of the neural canal is rather narrow in about the center of the lateral sides. They are posteriorly, at the axis, where it occupies about half of probably enlarged due to the compression onto the the breadth of the centrum. It becomes clearly broader centrum, but appear to have been present in the pre- anteriorly and is expanded almost over the entire compressed state too. breadth of the centrum of the atlas. Here also the neural The articular facet of the atlas is still connected to arches are slightly more robust than in the axis and the the occipital condyle and can thus not be observed, SACHS--REDESCRIPTION OF ELASMOSAURUS PLATYURUS 95

TABLE 2. Measurements of the vertebrae of ANSP 10081. CV = Cervical vertebrae; PV = pectoral vertebrae; DV = dorsal vertebrae; SV = sacral vertebrae; CAV = caudal vertebrae; a. = as measurable, i.c. = incomplete. ______whereas the articulation surface of the axis is clearly Cervical Vertebrae—Including the atlas-axis visible. It has a broad oval outline, with an excavation complex, a total number of 71 cervical vertebrae are for the neural canal in the middle of its dorsal edge, present (Figure 4D-K). Of these, only two are and a small notch at about the same level ventrally. The incomplete so that the series fits together almost facet itself is deeply concave and has robust, rounded perfectly and can also be reassembled on basis of the edges. Only the sections of the cervical ribs are original matrix that is still attached to many vertebrae. visible. At the right lateral side, they occur in the Most vertebrae are laterally compressed, with this posterior most section of the atlas and are prominently compression being stronger in the mid-cervical region, developed in the axis. than in the anterior or posterior sections. The The ventral side of the atlas-axis complex shows longitudinal lateral crest is well developed. It is slightly a distinct medial keel that runs between the anterior visible in the third cervical, clearly developed from the edge of the atlas and the posterior edge of the axis. 6th to the 45th and still visible to the 55th cervical Although only the basal section of this keel is vertebra, thus into the posterior section of the . preserved, it can be seen that it is transversally broader The position of the crest is in the middle of the centrum at the atlas. Lateral to the keel, the ventral surface is in the anterior vertebrae and in its dorsal half from longitudinally depressed. There is only a slight vertebra number 19 onwards. depression present in the atlas, whereas the depression The shape of the centra differs depending on the is more prominent in the axis. position in the neck. The third cervical is about as long

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FIGURE 1 Elasmosaurus platyurus Cope 1868. A. Dorsal view of premaxillae. B. Ventral view of premaxillae, with the vomeroventral fenestration visible posteromedially. Anterior portions of dentaries in C dorsal and D. ventral view. Scale = 5 cm. ______as broad. Beginning with the fourth cervical, the centra facets cannot always be stated accurately, due to the become longer than broad. The vertebrae are aforementioned compression. In the most anterior extraordinarily elongate in the mid-cervical region. In centra they are broad oval and moderately deepened. the posterior neck, they become again shorter and are The edges are rounded and thickened and show a clear rather broad, so that in number 61 the breadth and excavation in the middle of the dorsal and ventral side. length are about equal and the posteriormost cervicals In the more posterior section of the anterior neck (e.g. are broader than long. The shape of the articulation in number 25) the concavity of the ventral edge of the SACHS--REDESCRIPTION OF ELASMOSAURUS PLATYURUS 97

FIGURE 2. Elasmosaurus platyurus Cope 1868. Premaxillae in A. dorsal and B. ventral view. Abbreviations: lc = lingual concavitiy, indicating tooth position, sk = sagittal keel, vf = vomeronasal fenestrum.

______articulation facets becomes more prominent and the The rib facets are readily visible on all cervicals. shape of the facets is quadrate with rounded edges. They are situated laterally in the ventral section of the Cervicals number 38 – 49 are strongly deformed, vertebra almost throughout the cervical vertebral whereas numbers 50-60 are still in the matrix so that no column and they migrate dorsally only in the last three statement about their shape can be given. The centrum vertebrae. In the next to last cervical, they are situated of cervical number 63 is less compressed. Its in the middle of the lateral side of the centrum, are articulation facet is also rather quadrate in general prominently developed, and high ovals in outline. In shape, but with rounded edges. The facets of the most the last cervical vertebra they are situated somewhat posterior centra are broad oval in outline. more dorsally and have a more triangular outline. Here The neural arches are preserved in most cervicals. also, a distinct horizontal crest is formed anteriorly at Generally they are well fused with the centrum, so that the lower side of the rib facets. no suture is visible. The neural canal is rather narrow in In a number of vertebrae the cervical ribs are still the anterior cervicals and prominently developed in the attached to the centra, which are completely preserved most posterior ones. Here it is about as broad as high only in the anterior cervicals. In the fourth and fifth, and almost circular in the last cervical. Its shape cannot they are almost semicircular in lateral view, while in be observed in the mid-cervicals, due to crushing of the the seventh they are more quadrate. In all cases the centrum. cervical ribs are rather straight ventrally directed, The zygapophyses are present on a number of although this position could also be a result of the vertebrae. Pre- and post-zygapophyses are about equal lateral compaction. in length. The pre-zygapophyses reach over the level The ventral side of the centra is mostly not well the centrum with their entire length. This can be preserved. A pair of nutritive foramina is placed in the observed throughout the cervical vertebral column. The middle, separated by a short ridge. This ridge becomes post-zygapophyses reach over the level of the centrum more prominent towards posterior in the neck and is with about their posterior half. thickened in the most posterior cervical vertebrae. The neural spines are completely preserved only Pectoral Vertebrae—Three pectoral vertebrae in the 19th and 20th cervical vertebra. Here they are are preserved (Figure 5A). They are still in the matrix, rather low, so that its shape in the 20th cervical can be so that an anterior view is not possible. In the first described as almost semicircular in lateral view. pectoral centrum, the rib facets are triangular in outline

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FIGURE 3. Elasmosaurus platyurus Cope 1868. Additional cranial elements. A. Posteriormost part of the right maxilla. B Fragment B, C. Fragment C, toothbearing fragments probably belonging to the maxilla. D. Fragment D, possibly part of the anterior dentary. E Fragment E, F. Fragment F, toothbearing fragments from the posterior half of the jaw, G, H. Undeterminable fragment G in two views, I. Undeterminable fragment H. Scale = 5 cm. SACHS--REDESCRIPTION OF ELASMOSAURUS PLATYURUS 99

and are situated on small lateromedially-directed The rib facets are situated at a higher level than transverse processes. At their anterodorsal margins, a the neck of the transverse processes and are thus crest is formed that projects anteromedially and somewhat separated from them. They are broad oval to represents the border of the transverse process. Another rectangular in outline. The centrum of the ?fifth dorsal much smaller crest is developed at the bottom of the rib is almost circular; its articulation facets are only very facets, forming the ventral border of the transverse slightly concave. Also the lateral sides of the centrum process. In the second pectoral vertebra, the rib facets show a horizontal depression. are still triangular in cross-section, but are not as The next preserved centrum might represent the elongate ventrally as in the last cervical and first seventh or eight dorsal. Only the basal parts of the pectoral vertebra. Thus it has a more robust transverse processes are preserved. As in the ?fifth appearance. The dorsal margin of the transverse dorsal they are dorsoventrally narrow. The articulation processes is formed as a plate that is slightly oblique facets of the centrum are circular and the edges are ventrally. The anterior and posterior edges of this plate rather sharp, not well rounded as in the cervicals. Also form a clear ridge. The posterior surface of the a longitudinal concavity is present at the lateral sides of transverse process is directed straight vertically, the centrum, beneath the transverse processes. The next whereas the anterior one is smoothly curved vertebra is only represented by the centrum. Here the ventromedially. At the ventral portion of the transverse rib facets were situated clearly over the level of the process another, but clearly broader ridge is formed centrum, so that this vertebra might belong into the that is slightly curved, ventrally directed, and there mid-dorsal section. The last two vertebrae represent fused with the centrum in a broad base. The ventral another mid-dorsal, as well as large parts of a posterior sides of the centra bear a pair of nutritive foramina in dorsal vertebra. The mid-dorsal is completely the middle. They are separated by a broad ridge, which preserved (Figure 5B, C). The shape of its centrum is formed as a rounded back that becomes more corresponds with that of the previously described ones. expanded transversally towards the articulation facets. The rib facets are situated over the level the centrum. In the last pectoral vertebra, there is also a broad, but The transverse processes are very elongate. Their only slightly visible, ridge developed at the intersection dorsal surfaces are slightly horizontally curved from of lateral and ventral edges. In the third pectoral the edge of the neural spine to the rib articulation vertebra the rib articulation section differs from that of surface. The later is slightly vertically convex. The the second one in that it is situated more dorsally. The ventral margin is more prominently vertically convex. transverse processes are directed almost straight The anterior and posterior edges of the transversel vertically. A distinct ridge is present at the posterior processes bear sharp ridges. The shaft has a broad oval and ventral side of the processes, but both are not as cross-section. The rib facets are situated prominently sharp as in first two pectorals. The rib facets are broad higher than the shaft. They are slightly oblique and triangular in shape, with a long, straight dorsal posteriorly and are broad oval in outline. The pre- margin and shorter, ventromedially directed anterior zygapophyses are shorter than those of the cervical and and posterior sides. The mentioned ridge at the pectoral vertebrae and reach over the level of the intersection of the lateral and ventral edge is broader centrum only with about the anterior third of their and more distinct than in the next to last pectoral length. The post-zygapophyses are still very prominent vertebra. and reach over the level of the centrum with about the Dorsal Vertebrae—Of the dorsal vertebral posterior half of their length. The anterior hiatus is very column only six vertebrae are present, thus only about long, rather deep, and occupies about 60% of the length 1/3 of the actual number, compared with e.g. of the neural spines. It thereby thins out dorsally and Hydralmosaurus serpentinus where the number is 19 thus has an elongated triangular outline. The posterior (Welles, 1952). Cope (1869: 49) thought that 10 hiatus is much shorter and only about half as long as dorsals were missing; Welles (1952:54) believed the the anterior one. Dorsal of the hiatuses, the neural spine number was 18. The first and second preserved dorsals becomes extraordinarily thin as can be observed belong into the anterior section of the column and may posteriorly. The last vertebra that belongs in the represent positions four and five. The rib facets are posterior section of the column is only partially present situated at the level of the neural canal. The transverse on the left side as the transversel process, the pre- processes, which are completely preserved in the ?fifth zygapophyses and most of the centrum are missing. vertebra, are more flattened dorsoventrally (although The neural canal is circular and surrounded by very this is probably also effected by the compaction) and thick neural arches. The transverse process is shorter slightly oblique posterodorsally. The anterior and and more robust than in the previously described posterior sides of the processes bear a distinct ridge vertebra. Its basal sections at the neural arches are very along their margins. elongate anteroposteriorly and are broad ovals in cross section. Laterally, the process, and especially its

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FIGURE 4. Elasmosaurus platyurus Cope 1868. Cervical verterbrae. A-C Atlas-axis complex with attached occipital condyle in A. lateral, B. ventral and C. posterior view. D-K Ten anteriormost cervical vertebrae in lateral views. D. cervical vertebra 3, E. cervical vertebra 4, F. cervical vertebra 5, G. cervical vertebra 6, H. cervical vertebra 7, I. cervical vertebra 8, J. cervical vertebra 9, K. cervical vertebra 10. Scale = 5 cm. L-O. Cervical vertebra examples from the anterior-, mid- and posterior cervical region in lateral views (size reduced). L. cervical vertebra 20, M. cervical vertebra 30, N. cervical vertebra 40, O. cervical vertebra 49. Scale = 7 cm. SACHS--REDESCRIPTION OF ELASMOSAURUS PLATYURUS 101

FIGURE 5. Elasmosaurus platyurus Cope 1868. A. Last cervical and pectoral vertebrae in lateral view. B. Mid-dorsal vertebra in anterior and C. lateral view. D. Sacral vertebal column associate with the two anterior-most caudal vertebrae in lateral view. E. Posterior caudal vertebrae in lateral view. Scales = 9 cm. ______anterior side, curve posteriorly. It thereby becomes a centrum, but in its dorsal half and are only slightly high oval in outline, so that the lateral surface of the posteriorly directed. The anterodorsal ridge is longer anterior side of the process is formed as a high plate. than in the first sacral. In the third sacral, the rib facets The posterior edge is generally thinner and also forms a are also dorsoventrally elongated ovals and are situated distinct ridge in its medial half. The lateral half is at about the same level as in the second one, but are expanded dorsoventrally. The rib facet is oval in clearly more prominent and about twice as large as in outline. Of the hiatuses, only the posterior one is the first sacral centrum. They are slightly posteriorly visible. It is larger than in the previously described one orientated. The dorsal part of the transverse process is and occupies about 50% of the neural spine. The latter situated at about the same level as the dorsal edge of also has a very thin posterior edge above the hiatus. the neural canal. It is well rounded transversely and Sacral Vertebrae—An articulated series of four forms an anterior edge that is not as distinct as in the sacrals is present (Figure 5 D). In all vertebrae the second sacral. The rib facets of the fourth sacral are transverse processes are very short. In the first sacral, slightly larger than those of the third, and occupy the rib facets are situated in the posterodorsal section of almost the entire lateral margin of the centrum. The the centrum and are not as prominent as in the others. dorsal side of the transverse process is well rounded They are posteromedially directed and have a and therefore distinctly separated from the surface of somewhat triangular outline, with a concave anterior the centrum. The rib facets have an almost straight edge. On the dorsal side, a distinct, but short and lateral orientation. Basal fragments of the sacral ribs rather broad, anterior ridge is formed. In the second are attached to the second, third and fourth centrum. sacral vertebra, the rib facets are more prominent than The pre-zygapophyses are rather prominent and reach in the first and are dorsoventrally elongated oval in over the level of the centrum for almost their entire shape. They are situated posterior to the midline of the length. The post-zygapophyses are still connected to

102 PALUDICOLA, VOL. 5, NO. 3, 2005 the pre-zygapophyses so that no clear statement about to Turner that Hawkins was going to reconstruct their length can be given. The neural spines are present Elasmosaurus for a planned Paleozoic Park in New at the first and second vertebra, but are incomplete and York (Almy, 1987). However, this project somewhat compressed laterally so that the shape of the came to an end on May 3, 1871 when all of Hawkins hiatuses cannot be observed. The ventral sides of the work was destroyed by vandals (Colbert and Beneker, centra are well rounded and bear a pair of nutritive 1959). It might well be possible that the missing girdle foramina that is separated by a broad but low ridge. elements were in Hawkins workshop at that time and Caudal Vertebrae—A series of 18 caudal would have also been destroyed. Conspicuously, vertebrae is present, in which the first two are in the nothing about their loss was mentioned in Cope’s 1875 same block containing the sacral vertebrae (Figure 5D) publication. and are attached by matrix. The first caudal can clearly The illustrations provided by Cope (1869, 1870) be distinguished from the sacrals by the smaller size of are not very detailed, but still give an impression about the rib facets, which are only about half as large as the shape of the bones. One and the posterior those of the last sacral, and their position in the ventral part of another, as well as the anterior portions of both half of the centrum. They are almost circular in shape , had been preserved, whereas the pelvic and in the first and second caudal vertebrae also bear a girdle was complete. Welles (1952: 56-59) redescribed narrow horizontal keel in the middle of their dorsal the missing parts on basis of Cope's figures and side. The rib facets are situated in the ventral section of descriptions and concluded that (1) Cope’s claviculae the centra throughout the caudal vertebral column. or procoracoidea are the scapulae, as has been They become larger and broader oval in shape from the suggested before by Seeley (1874); (2) the fused third caudal vertebra onwards. In the 6th-13th vertebra, scapulae met in the midline with no trace of a median they are very large and occupy almost the entire bar; (3) the dorsal processes of the scapulae were very lateroventral margin of the centrum. In the 14th to 18th broad and the scapular neck was rather long; (4) the vertebra, the rib facets are still prominent but scapulocoracoid suture was probably running to the somewhat smaller compared to the size of the centra center of the glenoid; (5) the scapular foramen are too (Figure 5E). The edges of the facets are rather sharp in long in Cope's reconstructions and were separated by a the anterior caudals and become well rounded in the pectoral bar; (6) the anteromedial growth of the posterior ones. As in the other vertebrae, the pre- scapulae probably included the clavicular arch and (7) zygapophyses reach over the level of the centra for a pelvic bar was present. Welles (1952: 59) almost their entire length while the post-zygapophyses furthermore pointed out that in Cope's reconstruction reach over this level by about half of their length. The the greatest width of the pubes is at the front of the neural spines are rather completely preserved in the acetabulum, whereas in other elasmosaurs the pubes first, second, third and seventh caudal, but are have anterolaterally directed external borders. compressed laterally at their basis. Ventrally, the All other features, which can be taken from the surfaces for the haemapophyses are first clearly visible data provided by Cope (1869, 1870) are in the fifth caudal, although according structures are synapomorphic for the Elasmosauridae and shall slightly visible in the third and fourth caudal too, but therefore not be discussed. here no depressions for the articulation are present. The ventral margin of the centra is well rounded in the first, DISCUSSION second and third vertebra, rather plain and just slightly concave in the fourth and fifth centrum, and strongly Although relatively incomplete, the type transversally concave from the sixth to the 18th specimen of Elasmosaurus platyurus is of importance vertebra. It should be noted that Cope (1870) stated as it represents the first described and nominal member that some 30 caudals were missing, however, the usual of the Elasmosauridae and the only specimen clearly number of caudal vertebrae in elasmosaurs is around referable to this taxon. In the North American 30 (Welles, 1952). Cretaceous, elasmosaurs are common, but are Pectoral and Pelvic Girdles—Cope (1869, represented mostly by isolated skeletal elements. A 1875) described and figured large parts of the pectoral number of genera have been described based upon and pelvic girdles (Figure 6). These elements could not these remains (see Welles, 1952, 1962). In recent be located in the collection of the Academy of Natural reviews by Carpenter (1999) and Storrs (1999) many Sciences in Philadelphia. Williston (1906: 225) had taxa have been synonymized so that, besides already stated: “Unfortunately, the type specimen of Elasmosaurus, currently ten elasmosaur genera are Elasmosaurus no longer has the girdles described by known from the Cretaceous of North America. These Cope. What has become of them is not known”. are (in stratigraphic order): Carpenter Carpenter (1999: 152) pointed out that the girdles (1997, Britton Formation, ), possibly were destroyed while on loan to Waterhouse Welles (1943, and , Hawkins, who, with his assistant, prepared them out of -Campanian), Hydralmosaurus and the hard concretion (Cope, 1869: 51). Cope mentioned both Welles (1943, Niobrara Formation SACHS--REDESCRIPTION OF ELASMOSAURUS PLATYURUS 103

FIGURE 6. Elasmosaurus platyurus Cope 1868. Original reconstructions of the pectoral- and pelvic girdles of Cope (from Cope, 1869). A. Pectoral girdle, B. Pelvic girdle, C. . Not to scale. ______and formations, Campanian), either shorter than high or about as long as high. The Sato (2003, , only elasmosaur taxa where the condition present in Campanian), and , Welles (1943), Elasmosaurus platyurus is known are Styxosaurus Morenosaurus, Aphrosaurus, and Fresnosaurus all (Welles and Bump 1949; Sachs, 2004) and Welles, (1943, , ). The Hydralmosaurus (Cope, 1877). It thus can be latter genera Morenosaurus, Aphrosaurus and considered as an advanced feature (see also Carpenter Fresnosaurus are only based upon postcranial material. 1999, character 16; Sachs, 2004). In the following, the features of the type material of The number of cervical vertebrae is higher than Elasmosaurus platyurus are discussed and compared. 60 (for character discussion see Sachs, 2005, character Cranial Remains—The premaxilla bears more 18). Including the atlas-axis complex, the type than five teeth (for character discussion see Sachs, specimen of E. platyurus (ANSP 10081) has 71 2005: character 2). Primitively plesiosauroids and most vertebrae in the neck. Various researchers have given elasmosaurs have five teeth per premaxilla. Exceptions different numbers of cervical vertebrae for this among the Elasmosauridae are Terminonatator (Sato, specimen. According to Cope (1869, 1875), 68 1/2 2003) with nine teeth and 10-13 teeth per cervicals are present, to which he added another 3 1/2 premaxilla (Gasparini et al., 2003). that he mentioned as being lost. Wegner (1914) gives a The dentary symphysis extends to a point number of 60-78 cervicals; Welles (1949, 1952), between the fourth and fifth tooth in the dentary. This Brown (1981) and Storrs (1999) state 71 cervicals; condition is also present in Tuarangisaurus australis Carpenter (1997) reported 74 cervicals and then (Sachs, 2005), Hydrotherosaurus and Libonectes (Carpenter, 1999) revised his count to 72 cervicals; (Carpenter, 1997: fig. 2). For the other elasmosaurid Sachs (2005) mistakenly also stated 72 cervicals; taxa, the information is not provided in the literature. whereas Welles (1943) also stated that there were 74 Cervical Vertebrae—Atlas-axis complex is long cervicals. Williston (1906) gave a total of 76 vertebrae and low. In all sauropterygian taxa, except for some for the neck of Elasmosaurus. Apparently, some of the members of the Elasmosauridae, the axis centrum is

104 PALUDICOLA, VOL. 5, NO. 3, 2005 pectoral vertebrae have been included in the higher four sacrals are the usual number as seen in counts. Occitanosaurus (Bardet et al., 1999), Terminonatator More than 60 cervical vertebrae is a very (Sato, 2003), Styxosaurus (Sachs, 2004) or advanced number among the Plesiosauroidea. In the Hydralmosaurus (Welles, 1952). Only three are present Jurassic elasmosaurid Occitanosaurus the number is 43 in (Wegner, 1914), Thalassomedon (Bardet et al., 1999). However the (Welles, 1943), Morenosaurus (Welles, 1943), and elasmosaurid Brancasaurus has only 37 cervical Hydrotherosaurus (Welles, 1943). The number is vertebrae (Wegner, 1914). The number is higher than unknown in Libonectes (Welles, 1949), 60 in Libonectes (=62, Carpenter, 1999), Tuarangisaurus (Wiffen & Moisley, 1986; Sachs, Thalassomedon (=62, Welles, 1943), Styxosaurus (=62, 2005), (Welles, 1962) Aristonectes Carpenter, 1999) and Hydralmosaurus (=63, (Gasparini et al., 2003), Aphrosaurus (Welles, 1943) Carpenter, 1999). The number of cervicals is unknown and Fresnosaurus (Welles, 1943). in Aphrosaurus, Fresnosaurus and Morenosaurus The tail is relatively complete, consisting of 18 (Welles, 1943). The only sauropterygian where the vertebrae, but like the dorsal vertebrae also caudals are number of cervical vertebrae is higher than 70 is not diagnostic among Cretaceous elasmosaurs and can Elasmosaurus platyurus, accordingly this character is a thus not be used for comparisons. clear autapomorphy of Elasmosaurus and can be Pectoral and Pelvic Girdle—As mentioned considered as an advanced feature. before, the pectoral and pelvic girdles are lost, so that The anterior cervical vertebrae are long and low the comparative observations are totally based upon the (for character discussion see Sachs, 2005: character descriptions and figures of Cope (1869, 1870) and the 17). As with the axis centrum, the shape of the anterior conclusions and figure of Welles (1952). cervical vertebrae is usually either high and short (e.g. In the pectoral girdle the most conspicuous in the , Tarlo, 1960) or about as long as feature is the long pectoral bar. Carpenter (1999) high (e.g. in the Plesiosauridae, Brown, 1981). The discussed this feature and mentioned that according to centra become longer than high in most elasmosaur Brown (1981) there is an ontogenetic variation of this taxa, like Styxosaurus (Sachs 2004), Hydralmosaurus character (demonstrated with an ontogenetic series of (Cope, 1877), Libonectes (Welles, 1949), Crpytoclidus eurymerus Phillips, 1871), in which the Occitanosaurus (Bardet et al., 1999), Callawayasaurus bar is absent in juvenile and present in adult (Welles, 1962), Terminonatator (Sato, 2003), individuals. Carpenter (1999) states that in Hydrotherosaurus (Welles, 1943) and Tuarangisaurus and in some plesiosaurids, the bar is not developed in (Wiffen and Moisley, 1986; Sachs 2005). The adult specimen, thus its absence must be considered as condition is unknown in Aphrosaurus, Fresnosaurus the plesiomorphic condition. Accordingly the presence and Morenosaurus (Welles, 1943). of the pectoral bar in Elasmosaurus platyurus is an A longitudinal lateral crest is present in the advanced feature. anterior cervical vertebrae. This character has been On the scapula, the coracoidal margin appears to discussed before by Brown (1981, 1993), Carpenter be about as long as the glenoideal one. (1999) and Sachs (2004) and is synapomorphic for the Synapomorphically, the coracoidal margin is longer Elasmosauridae. (usually 1.5 times) than the glenoidal one (Sachs, Pectoral and Dorsal Vertebrae—Three 2004), although we don’t know how exact Cope’s pectorals are known in Occitanosaurus (Bardet et al. (1869) figure is in this respect. Also, the pelvic girdle 1999), Brancasaurus (Wegner, 1914), Styxosaurus has a rather unusual shape in Cope's reconstruction. (Welles and Bump, 1949), Thalassomedon (Welles, Here the pubes are very prominent and are medially 1943), Aphrosaurus (Welles, 1952), and connected over their entire length. Their anterior edge Hydralmosaurus (Welles, 1952), thus this number is is anterolaterally directed and almost straight, not common among the Elasmosauridae, although there are gradually curved as usual in elasmosaurs. Also, the only two pectorals present in Callawayasaurus (Welles ischia are connected medially so that along the length 1962), Morenosaurus (Welles, 1952), and of the pelvic girdle a medial pelvic bar is present. The Hydrotherosaurus (Welles, 1943). The number is latter is the most conspicuous feature because a bar is unknown for Tuarangisaurus (Wiffen and Moisley, usually not present in plesiosaurs. Among the 1986; Sachs, 2005), Fresnosaurus (Welles, 1952) and Elasmosauridae, a pelvic bar is known in Brancasaurus Aristonectes (Gasparini et al., 2003) and is not brancai from the Lower Cretaceous () of provided for Libonectes (Welles, 1949). Germany and in a specimen from the Upper Cretaceous Dorsal vertebrae are not diagnostic at genus level (Campanian-Maastrichtian) of Patagonia, described by in the Upper Cretaceous elasmosaurs and are thus not Gasparini & Salgado (2000) as Elasmosauridae gen. et useful for comparison. sp. indet. Of the latter, other elements also are similar Sacral and Caudal Vertebrae—The number of in shape to ANSP 10081. However, on basis of the sacral vertebrae is four in the type specimen of preserved material, it cannot be judged whether both Elasmosaurus platyurus. Among the Elasmosauridae specimens are congeneric. SACHS--REDESCRIPTION OF ELASMOSAURUS PLATYURUS 105

Nicholls, (eds.), Ancient Marine , RESULTS OF THE DISCUSSION Academic Press, San Diego. Carpenter, K. 1999. Revision of North American As shown here, Elasmosaurus platyurus elasmosaurs from the Cretaceous of the western comprises two clear autapomorphies; the presence of interior. Paludicola 2:148-173. six teeth per premaxilla and 71 cervical vertebrae. Colbert, E. and K. Beneker. 1959. The Paleozoic Additionally, it shows one feature-complex that is Museum in Central Park, or the museum that unique within the Elasmosauridae: four sacral never was. Curator 2:137-150. vertebrae + presence of a pelvic bar. Elasmosaurus Cope, E. D. 1868. Remarks on a new enaliosaurian, also shows two advanced feature complexes that are Elasmosaurus platyurus. Proceedings of the also only present in Styxosaurus and Hydralmosaurus: Academy of Natural Sciences of Philadelphia (1) long and low axis centrum + anterior cervical centra 1868:92-93. long and low. (2) number of cervicals higher than 60 + Cope, E. D. 1869. Synopsis of the Extinct Batrachia three pectoral vertebrae. Elasmosaurus is more Reptilia, and Aves of North America. Part I. advanced than most elasmosaur taxa as shown by the Transactions of the American Philosophical presence of six premaxillary teeth, a long and low axis Society, New Series 14:1-104. centrum, the high number of 71 cervical vertebrae and Cope, E. D. 1870. Synopsis of the extinct Batrachia, the development of both a pectoral and a pelvic bar. A Reptilia and Aves of North America. Part II. close relationship of Elasmosaurus platyurus with Transactions of the American Philosophical Styxosaurus and Hydralmosaurus can be concluded on Society, New Series 14:105-252. basis of the present material. Cope, E. D. 1875. The Vertebrata of the Cretaceous formations of the West. Report of the United ACKNOWLEDGMENTS States Geological Survey of the Territories, pp. 1-303. I am grateful to Dr. Ted Daeschler (ANSP) for his Cope, E. D. 1877. Report on the geology of the region kind support during my stay at the Academy and for of the Judith River, Montana, and on vertebrate his help with the photos. I also thank the two reviewers obtained on or near the Missouri River. Kenneth Carpenter and Tamaki Sato, as well as Mike Bulletin of the Geological and Everhart for helpful comments. This project was Geographical Survey 3:565-597. supported by a Jessup Fellowship of the Academy of Davidson, J. P. 1997. The bone sharp. The life of Natural Sciences, Philadelphia. Edward Drinker Cope. Academy of Natural Sciences of Philadelphia Special Publications LITERATURE CITED 17:1-237. Davidson, J. P. 2002. Bonehead mistakes: The Almy, K. 1987. Thof’s dragon and the letters of Capt. background in scientific literature and Theophilus H. Turner, M.D. Army. Kansas illustrations from Edward Drinker Cope's first History 10: 170-200. restoration of Elasmosaurus platyurus. Bardet, N., P. Godefroit, and J. Sciau. 1999. A new Proceedings of the Academy of Natural Sciences elasmosaurid plesiosaur from the lower Jurassic of Philadelphia 152:215-240. of southern . Palaeontology 42:927-952. Gasparini Z, and Salgado L. 2000. Elasmosáuridos Blainville, H. D. de. 1835. Description de quelques (Plesiosauria) del Cretácico Tardío del norte de espèces de reptiles de la Californie, précédée de Patagonia. Revista Español de Paleontología l'analyse d'un système général d'Erpetologie et 15:13-21. d'Amphibiologie. Nouvelle Annales de la Gasparini Z., Bardet N., Martin J., and Fernández M. Museé de histoire Naturelles de Paris 3:233-296. 2003. The elasmosaurid plesiosaur Aristonectes Brown, D. S. 1981. The English Upper Jurassic cabrera from the latest Cretaceous of South Plesiosauroidea (Reptilia) and a review of the America and Antarctic. Journal of Vertebrate phylogeny and classification of the Plesiosauria. Paleontology 23:104-115. British Museum (Natural History) Bulletin, Gray, J.E. 1825. A synopsis of the genera of reptiles Geology Series 35: 253-347. and Amphibia, with a description of some new Brown, D. S. 1993. A taxonomic reappraisal of the . Annales of the Philosophical Society of families Elasmosauridae and Cryptoclididae London 26:193-217. (Reptilia: Plesiosauroidea). Revue de Paléo- Phillips, J. 1871. Geology of Oxford and the valley of biologie, Special Volume 7:9-16. the Thames. 523 pp. Oxford. Carpenter, K. 1997. Comparative cranial anatomy of Sachs, S. 2004. Redescription of Woolungasaurus two North American Cretaceous plesiosaurs. glendowerensis (Plesiosauria: Elasmosauridae) Pp. 191-216 in J. M. Callaway and E. L. from the Lower Cretaceous of Northeast

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Queensland. Memoirs of the Queensland Branca Festschrift, Gebrüder Borntraeger, Museum 49:215-233. . Sachs, S. 2005. Tuarangisaurus australis sp. nov. Welles, S. P. 1943. Elasmosaurid plesiosaurs with a (Plesiosauria: Elasmosauridae) from the Lower description of the new material from California Cretaceous of northeastern Queensland, with and Colorado. University of California Memoirs additional notes on the phylogeny of the 13:125-254. Elasmosauridae. Memoirs of the Queensland Welles, S. P. 1949. A new elasmosaur from the Eagle Museum 50:429-444. Ford Shale of . Fondren Science Series Sato, T. 2003. Terminonatator ponteixensis, a new 1:1-28. elasmosaur (Reptilia: ) from the Welles, S. P. 1952. A review of the North American Upper Cretaceous of Saskatchewan. Journal of Cretaceous elasmosaurs. University of Vertebrate Paleontology 23:89-103. California Publications in Geological Sciences Seeley, H. G. 1874. Note on some of the generic 29:47-143. modifications of the plesiosaurian pectoral arch. Welles, S. P. 1962. A new species of elasmosaur from Quarterly Journal of the Geological Society of the of Columbia and a review of the London 30:436-449. Cretaceous plesiosaurs. University of California Storrs, G. W. 1984. Elasmosaurus platyurus and a page Publications in Geological Sciences 44:1-96. from the Cope-Marsh war. Discovery 17:25-27. Welles, S. P., and J. Bump. 1949. Alzadasaurus Storrs, G. W. 1999. An examination of Plesiosauria pembertoni, a new elasmosaur from the Upper Diapsida: Sauropterygia) from the Niobrara Cretaceous of South Dakota. Journal of Chalk (Upper Cretaceous) of central North Paleontology 23:521-535. America. University of Kansas Paleontological Wiffen, J. and W. L. Moisley. 1986. Contributions 11:1-15. reptiles (Families Elasmosauridae and Tarlo, L. B. 1960. A review of the Upper Jurassic Pliosauridae) from the Mangahouanga Stream, pliosaurs. British Museum (Natural History) North Island, . New Zealand Bulletin, Geology Series 4:145-189. Journal of Geology and Geophysics 29:205-252. Wegner, T. 1914. Brancasaurus brancai n. g., n. sp., Williston, S. W. 1906. North American plesiosaurs: ein Elasmosauride aus dem Wealden Elasmosaurus, , and . Westfalens. Pp. 234-305 in F. Schoendorf (ed.) American Journal of Science Series 4, 21:221- 234.

Corrections p. 92: Systematic Palaeontology – Elasmosaurus platyurus Cope, 1869 p. 92: Material – 71 cervical vertebrae, including the atlas-axis complex p. 104: Pectoral and Pelvic Girlde – eurymerus (Phillips, 1871)