| The middle Eocene Wasatch and Bridger formations of the Green River Basin of Wyoming have yielded abundant remains of fossil amphibians, lizards, amphisbaenians, and snakes.; Latest Wasatch (Wa7) and earliest Bridgerian (Br0) basin margin assemblages have been recovered from near South Pass on the northeastern margin of the basin and from the Desertion Point-Little Muddy section on the western margin. Early Bridgerian (Br1) basin center faunas are represented by collections from Desertion Point-Little Muddy and Big Island. The Bridger Basin contains basin center assemblages ranging in age from Br1 through Br3 (middle to late Bridgerian).; Lostcabinian (Wa7) and Gardnerbuttean (Br0) assemblages were poorly known before recent collections at South Pass. These levels contain the lizards Glyptosaurus sylvestris, Machaerosaurus torrejonensis, Saniwa ensidens, Palaeoxantusia sp., Xestops vagans, Parasauromalus olseni, Restes rugosus , glyptosaurine "inlet A", an amphisbaenid; and the snakes Dunnophis microechinis, Boavus occidentalis, Calamagras primus, Coniophis sp., a rhinophrynid, and a salamander. "Bridgerian A" (Br1) assemblages contain the lizards Glyptosaurus sylvestris, Xestops vagans, Parasauromalus olseni, Saniwa ensidens, an amphisbaenid; and the snakes Boavus occidentalis, and Coniophis sp., and record the earliest appearances of the lizards Paraglyptosaurus hillsi, Palaeoxantusia fera, and Tinosaurus stenodon. Taxa recovered from the "Bridgerian B" and "Bridgerian C" (Br2 and lower Br3) include all lizards found in older levels and the earliest appearances of Palaeoxantusia borealis , Tinosaurus pristinus, Eodiploglossus borealis , and Apodosauriscus minutus.; The diversification of this lizard assemblage through time is a reflection of climatic warming which occurred during the late Wasatchian through middle Bridgerian but also may be influenced by the smaller sample size of principally basin margin assemblages for Wa7 and Br0.; The fossil assemblages and sedimentary stratigraphy at South Pass indicate the presence of an alluvial fan produced by reverse movement on the Continental and Wind River faults. This basin margin environment provided diverse habitats which in turn supported a wide variety of amphibian, lizard, amphisbaenid, and snake species. |
