SAURIA

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 : 351-352

ORDER SAURIA

With the greater collecting efficiency achieved by the use of screening methods, not only has the taxonomy of small mammals become clearer but so has that of other small vertebrates, notably lizards.

The lizards are represented by a fragmentary assortment of dentaries, maxillae, and vertebrae. Most of the jaw pieces reveal the presence of well-worn or digested teeth. Some of the better preserved specimens come from Clayball Hill, where the productive layer is a silty shale in which the delicate bones are less fragmented than in the bone concentrate from Clambank Hollow. There are no differences among the identifiable lizards of the Judith River Formation, Montana, and the Lance Formation, Wyoming, at the species level.

Gilmore (1928, 1938) was the pioneer in the study of Cretaceous lizards and snakes. Gilmore (1943) also discussed the lizards obtained from the Djadochta Formation of Mongolia and described nine genera representing the families Agamidae , Chamaeleontidae , Ametosauridae, Amphisbaenidae , Varanidae , and Anguidae . Commendable as his efforts were, they were hampered by the fragmentary and eroded nature of his material and by insufficient Recent comparative material. Consequently Estes (1964) revised the lizard genera recovered from the Lance Formation, Wyoming.

The lizard fauna of the Campanian, in comparison with the Maestrichtian, was quite poorly known until the current investigation, as no lizard genus had been reported from the Judith River Formation. Of the two genera described from the Oldman Formation of Alberta as lizards, Palaeosaniwa canadensis Gilmore (1928) and Polyodontosaurus grandis Gilmore (1932) , only P. canadensis is actually a lizard. Sternberg (195 1) and McDowell and Bogert (1954) showed that P. grandis was a dinosaur.

The lacertilian fauna was collected chiefly from Clayball Hill and Clambank Hollow, and is composed of six genera and six species previously known from the Lance Formation.

The presence of a new genus of lizard in the Judith River Formation is indicated by a number of varanoid-like vertebrae. These vertebrae cannot as yet be associated with any of the dentaries or maxillae in the collection. They are smaller and structurally dissimilar to the vertebrae of Palaeosaniwa canadensis , but resemble, in certain features, the ophidian, Coniophis . Other specimens are present in the Judith River Formation which are evidently different from those of the Lance Formation, but the material is too fragmentary and inadequate to make a meaningful comparison.