A new fossil lizard from the Lower Cretaceous Sasayama Group of Hyogo Prefecture, western Honshu, Japan

Abstract

ABSTRACT—A new fossil lizard of the genus Pachygenys is described on the basis of a single, partially broken right mandible excavated from an unnamed formation of the Lower Cretaceous Sasayama Group in Hyogo Prefecture, western Honshu, Japan. The mandible exclusively shares a few apparently highly specialized morphological features, such as distinct foreshortening of the dentary tooth row and reduced dentary tooth number (nine), with Pachygenys thlastesa, the type species of the genus from the Lower Cretaceous of eastern China. However, the new species differs from the latter in having a shorter tooth row, anterior and middle teeth with unicuspid crowns (vs. bluntly truncated crowns in the latter), and posterior teeth with unicuspid and simple conical crowns (vs. bluntly truncated crowns in the latter). The specimen described here represents the first unequivocal fossil record of lizards in Japan, with its congeneric species occurring almost concurrently in eastern Eurasia.

http://zoobank.org/urn:lsid:zoobank.org:pub:C1B5D494-AE63-41C0-BB81-7324F49DD1C1

ACKNOWLEDGMENTS

We thank K. Adachi for the discovery of, and information on, the productive fossil site of the Sasayama Group, from which the type specimen of the new species described in this paper was collected. We also thank M. Manabe (NSMT) and T. Tsuihiji (UT) for technical assistance. Special thanks are due to Y. Fujie (formerly Takahashi) and other museum staff and volunteers who helped us with the excavation and preparation of the specimen. S. Evans and an anonymous reviewer are acknowledged for their constructive criticisms on an earlier draft. This study was supported in part by a Grand-in-Aid for Scientific Research from the Japan Ministry of Education, Culture, Sports, Science and Technology (B-20340145; Project Leader, Haruo Saegusa).

Handling editor: Jack Conrad.