736


Journal of Paleontology 92(4):734–742


1986 aff. Pelecymala; Fraser, p. 176, pl. 20, figs. 8, 9. 1988 Clevosaurus sp.; Fraser, p. 163, fig. 43. 1993 Clevosaurus latidens Fraser, p. 137, fig. 2.


Holotype.—VMNH 524, maxillary fragment (Fig. 1.1–1.3). Additional specimens.—VMNH 525–528, AUP 11191–11192.


Remarks.—The systematic paleontology section of Fraser’s original work referred to the holotype of Fraserosphenodon latidens (VMNH 524) as a dentary fragment (Fraser, 1993), but the description of this element treated it as a maxillary fragment. Our review of VMNH 524 confirms that it is a fragment of the posterior part of the left maxilla (Fig. 1.1–1.3). This element includes five well-preserved, complete teeth. The maxillary teeth have relatively short crowns with transversely broadened posterolabial flanges without grooved facets on the labial sur- face and heavily worn occlusal surfaces. We agree with Fraser (1993) that paratype specimen


VMNH 525 is a dentary fragment that possibly belongs to the right dentary (Fig. 1.4–1.6). This element has three teeth that are also transversely broadened. In labial view, all teeth appear distinctly triangular. Only the second and third teeth are heavily worn, and the wear is especially pronounced on the third tooth. In occlusal view, the teeth of VMNH 525 appear round with a bulbous swelling developed medially on each tooth, as was described by Fraser (1993) for specimen VMNH 543. The overall shape of both VMNH 525 and 543 is also quite similar. Note that Fraser (1993) did not mention specimen VMNH 543 in the systematic paleontology section of his paper, and there is also no specimen in theVMNHcollection assigned to Fraserosphenodon (C. latidens) with that catalog number. It might be that specimen VMNH 543 illustrated and described by Fraser (1993, fig. 2C–E) is indeed specimen VMNH 525. Paratypes VMNH 526–528 are maxillary fragments


(Fig. 1.7–1.15). Specimens VMNH 526 and 528 (Fig. 1.7–1.9, 1.13–1.15) belong to the distal part of the left maxilla, whereas VMNH 527 (Fig. 1.10–1.12) belongs to the mesialmost part of the right maxilla. VMNH 526 and 528 include a series of four complete teeth, which are heavily worn on the occlusal surface, and have a morphology comparable to that of the holotype. The crowns of VMNH 528 are a little higher than in the other specimens (Fig. 1.13–1.15). VMNH 527 includes six complete teeth and a very small fragment of a broken tooth in the distal part of the element (Fig.1.10–1.12). The mesialmost tooth of this specimen is very small and rounded; the following tooth is also very small and of a semioval shape. The third to sixth teeth are all transversely broadened, with a right-angled triangular shape in labial view and a heavily worn occlusal surface. Paratype VMNH 529, a maxillary fragment according to Fraser (1993), could not be located within the VMNH collection. The heavily worn occlusal tooth surfaces in all type


specimens suggest that they might belong to adult individuals (Fig. 1). A recent study of ontogenetic variation of the dentary in rhynchocephalians (Romo de Vivar-Martínez and Bento-Soares, 2015) demonstrates that the occlusal surface of teeth shows high wear in mature specimens.


Additionally, another six specimens from the AUP


was originally identified as Clevosaurus sp. by Fraser (1988) and was subsequently reassigned to C. latidens by Fraser (1993). The nasal process is broken in AUP 11191, but the ventral and dorsal maxillary processes are well preserved. The distal end of the ventral maxillary process has a clearly flattened oval shape; the dorsal maxillary process is relatively long and is angled at ~60o relative to the ventral maxillary process. On the convex dorsal surface of the premaxilla, between the dorsal maxillary process and the nasal process, it is possible to observe the premaxillary fossa, which is semicircular in shape. AUP 11191 exhibits three complete teeth, of which the distalmost tooth is very small, considerably shorter in relation to the other two teeth. In contrast, the two mesialmost teeth are of regular size and partially fused, and both have a rounded semicircular shape with minor signs of wear. The semifused condition of the two mesialmost teeth of AUP 11191 suggests that this specimen is a juvenile: as seen in other derived rhynchocephalians (e.g., Clevosaurus and Sphenodon spp.) these teeth fuse over time in mature individuals to form the characteristic chisel-like structure seen in late-diverging rhynchocephalians (Robinson, 1973).


Specimen AUP 11192, an anterior fragment of a right


dentary (Fig. 2.3–2.5), was tentatively assigned to Pelecymala Fraser, 1986 by Fraser (1986), but as in the case of AUP 11191, it was later referred to C. latidens by Fraser (1993). In the description of AUP 11192, Fraser (1986) noticed that the length of this specimen appeared quite similar to that of C. hudsoni, but was noticeably deeper in height. AUP 11192 has a robust and deep structure, similar to that of opisthodontians (e.g., Priosphenodon Apesteguía and Novas, 2003, Toxolophosaurus Olson, 1960). The mandibular symphysis in AUP 11192 is quite wide; the Meckelian canal runs along the midline of the jaw.


collection can be referred to Fraserosphenodon. However, apart from AUP 11191 and 11192 (premaxilla and dentary, respectively), the other four specimens attributable to Fraserosphenodon are all fragmentary maxillary elements. All of these maxillary elements were stored in containers with other rhynchocephalian specimens without being labeled individually, making it impossible to associate the specimens with unique catalog numbers. These specimens all clearly exhibit the characteristic transversely broadened tooth morphol- ogy without grooved facets on the labial tooth surfaces, with heavy wear on the occlusal surface. The first specimen is a fragment of a right maxilla. It has four heavily worn teeth that include a small rounded tooth between the second and third tooth, which might represent a dental pathology. The second specimen is a fragment of a right maxilla that includes two isolated but complete teeth. The third specimen is a fragment of a right maxilla and includes four teeth. The mesialmost tooth of this specimen is heavily eroded and the tooth enamel of the third tooth is slightly damaged. The fourth specimen is a fragment of the distal end of a left maxilla; it includes two teeth with very short crowns due to the heavy wear of the occlusal surface. Among all rhynchocephalian specimens in the AUP collection, we did not identify any dentary specimens attributable to Fraserosphenodon with preserved coronoid processes (contra Fraser, 1993). Specimen AUP 11191, a right premaxilla (Fig. 2.1, 2.2),


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