NEW VERTEBRATE FOSSILS FROM THE PIPE CREEK SINKHOLE (LATEST HEMPHILLIAN, GRANT COUNTY, INDIANA)

Excavation of in situ sediments at the Early Pliocene Pipe Creek Sinkhole site near Swayzee, Indiana, and screen washing of sediments, has revealed new information about the structure and paleontology of the site. Sediment was removed down to bedrock. The fossiliferous deposit was funnel-shaped, with sediment in the plugged drainage hole more than two meters in vertical (not bed) thickness; turtle shells and other elongate objects were nearly vertically oriented in this neck of the funnel.

Numerous tiny steinkerns of bivalves and gastropods (commonly retained on a 1-mm mesh screen) were found, in marked contrast to the absence of large molluscs in the fauna. Several new vertebrate taxa were discovered: Elaphe cf. E. vulpina (fox snake), Lampropeltis cf. L. triangulum (milk snake), cf. Heterodon (true hognose snake), Dipoides (beaver), a shrew, a small mustelid, a badger, and a felid comparable in size to a small cougar.

The snake fauna is an interesting mixture of extinct and extant forms (e.g. extinct Paracoluber and extant Coluber [racers], extinct Paleoheterodon and extant Heterodon [hognose snakes]), as expected for a transitional interval like the Hemphillian North American Land Mammal Age. The mammalian fauna is becoming quite diverse for so small a site, with at present one species each of soricid, talpid, castorid, sciurid, geomyid, lagomorph, cervoid, tayassuid, ursid, felid, and rhinocerotid, four murids, two mustelids, three canids, and three camelids. Surprisingly, still no equids have been found.