Polyglyphanodon sternbergi Gilmore, 1940 is a large-bodied lizard from the Late Cretaceous of North America distinguished by its transversely oriented, interlocking teeth. Initially the teeth of P. sternbergi were described as smooth and blade-like, but recent discoveries of new specimens from the type locality and re-examination of the original material indicate that the chisel-like teeth of P. sternbergi have small, irregular serrations along the blades. These serrations are similar in size to those found on the teeth of the modern herbivorous lizard Iguana iguana and were likely used in a similar manner to crop vegetation, but was also capable of a degree of oral food processing due to the transverse orientation and interlocking arrangement of the dentition of P. sternbergi. Additionally, the presence of transversely oriented teeth with V-shaped blades in the anterior portion of the tooth row of P. sternbergi represents an additional shared characteristic in tooth structure between P. sternbergi and Dicothodon moorensis, Bicuspidon numerosus, and Peneteius aquilonoius; all transversely-tooth polyglyphandontine lizards from the Cretaceous of North America. It appears that the unique dentitions of Polyglyphanodon sternbergi (large teeth with transverse, serrated blades) and Peneteius aquilonius (small teeth with mammal-like specializations) present by the end of the Cretaceous were derived from a bicuspid, transversely oriented precursor tooth with a V-shaped blade.

Key words: Squamata, Polyglyphanodontinae, Polyglyphanodon, dentition, Cretaceous, North America.

Randall L. Nydam [rnydam@midwestern.edu] Arizona College of Osteopathic Medicine, Midwestern University, 19555 N. 59th Ave., Glendale, AZ 85308, USA; Richard L.Cifelli [rlc@ou.edu] Oklahoma Museum of Natural History, 2401 Chautauqua Ave., Norman, OK 73072, USA.