Paraderma bogerti Estes, 1964

Sahni, Ashok, 1972, The vertebrate Fauna of the Judith River formation, Montana, Bulletin of the American Museum of Natural History 147 (6), pp. 319-416 : 357-358

Paraderma bogerti Estes, 1964

Figure 8I

Paraderma bogerti was originally described from the Lance Formation of Wyoming by Estes (1964). AMNH 8504, from Clambank Hollow, is the only fragment that can be referred to Paraderma bogerti from the Judith River Formation (fig. 8I). The teeth are pleurodont, and have transversely expanded and prominently infolded bases. AMNH 8504 is slightly smaller than UCMP 54261, a left maxilla described and figured by Estes (1964, p. 133).

DISCUSSION: The parasaniwids are represented by two genera, Parasaniwa and Paraderma , in the Judith River, Lance, and Hell Creek formations. These are quite distinct from contemporary lizards and are generically separable from each other by a number of characteristics discussed by Estes (1964). Paraderma differs from Parasaniwa in stoutness, in having fewer teeth, external maxillary sculpturing, and in the form of the maxilla.

The family Parasaniwidae was proposed by Estes (1964) for the reception of Parasaniwa and Paraderma . The relationship of this family to others is not clear as yet, although Estes believed the parasaniwids are primitive platynotans with some resemblances to the diploglossans. Estes (1964, p. 128) defined the family as follows: "teeth with simple basal fluting extending in to the medullary cavity; development of an intramandibular jaw hinge; unretracted nares; skull roof with well-defined scute areas; scutes tending towards multiplication." It is distinguished from the Varanidae by "the lack of complicated infolding of the tooth base into the medullary cavity and the lack of naris contraction."

A varanid, Palaeosaniwa canadensis , has been described from the Oldman Formation, Alberta, on the basis of a dorsal vertebra which closely resembles the living Varanus in structure. This species has not been found in the Judith River Formation and its absence is attributed to the rarity of the form and the fortunes of sampling. The type specimen, USNM 10864, was found near Steveville along the Red Deer River close to the localities from which Campanian marsupials have been recovered.

Telmasaurus grangeri , based on specimen AMNH 6645, was described by Gilmore (1943, p. 379) from the Djadochta Formation of Mongolia as a varanid related to Saniwa , Palaeosaniwa , and Parasaniwa . The general tooth form and size, judged from the illustrations by Gilmore (1943, p. 381), is similar to varanids rather than parasaniwids in that the teeth are sabreshaped and curved posteriorly.

The varanids of the Campanian and Maestrichtian are large and comparable in size to some Recent forms. According to Estes (1964, p. 169), Palaeosaniwa canadensis was as large as the modern "komodo dragon," Varanus komodensis , and shared with it a number of common features. Palaeosaniwa was probably an active predator, and could have preyed on the smaller multituberculates and marsupials. Paraderma and Parasaniwa are similar in many respects to Heloderma , but little can be said about their ecologic characteristics until more information is forthcoming.

Figures

FIG. 8. A. Chamops segnis. AMNH 8486, labial view of left dentary. B. Lingual view. Both x 5. C. AMNH 8488, lingual view of left maxilla. D. Labial view. Both x 5. E. cf. Xenosauridae, AMNH 8498, labial view of left maxilla. F. Lingual view. Both x 5. G. Peltosaurus piger, AMNH 8495, lingual view of left maxilla, x 5. H. AMNH 8494, lingual view of right dentary, x 5. I. Paraderma bogerti, AMNH 8504, lingual view of right maxilla. x 5. J. Parasaniwa wyomingensis, AMNH 8499, lingual view of left dentary, x 5. K. Leptochamops denticulatus, AMNH 8491, lingual view of right maxilla, x 5. L. Exostinus lancensis, AMNH 8497, lingual view of right maxilla, x 5. M. Deinodon horridus, AMNH 8513, posterior view of isolated tooth. N. Lateral view. Both x 13. 0. AMNH 8515, lateral view of anterior dentary tooth. P. Posterior view. Both x 13. Q. AMNH 8514, posterior view of?premaxillary tooth. R. Lateral view. Both x 12. S. Paronychodon lacustris, AMNH 8522, lingual view of isolated tooth. T. Labial view. Both x 12. U. Kritosaurus cf. K. breviceps, AMNH 8525, lateral view of isolated tooth. V. Posterior view. Both x 1 2. W. Procheneosaurus altidens, AMNH 8527, labial view of isolated tooth. X. Anterior or posterior view. Both x 12. Y, Z.?Sebecosuchia, AMNH 8549, views of an solated tooth. Both x 10.