INTRODUCTION

The lower and middle Siwalik Group of the Potwar Plateau (Miocene, approximately 18 to 3.5 Ma), Pakistan is an extensive, continuous fluvial sequence derived from the Himalaya foredeep that preserves a rich vertebrate fossil record and evidence of climatic and environmental transitions reflected in sedimentary and chemical records. These characteristics combined with fine chronostratigraphic control have allowed for precise studies of the relationship between vertebrate faunal evolution and environmental change through time within a geographically restricted study area (approximately 2,500 km2; Badgley and Behrensmeyer 1995). These studies have recorded patterns of immigration and diversity change that reflect both continental-scale biogeographic histories and more localized changes in feeding ecology and diversity in response to floral transitions and increasing seasonality and aridity through time driven by the inception of the Asian monsoonal precipitation system (e.g., Flynn and Jacobs 1982; Barry et al. 1991; Badgley and Behrensmeyer 1995 and references therein; Barry et al. 2002). All of this research has focused on the fossil mammal record, and no attempts have been made to examine the Siwalik Group reptile record in terms of either rigorous systematics or relationship to environmental change. In this analysis, I describe the snakes from the Siwalik Group, examine changes in composition of the snake record through time, and compare the record to environmental histories recorded in the Siwalik Group.