TAPHONOMY OF TWO MIOCENE RHINOCEROS ASSEMBLAGES, DECATUR COUNTY, KANSAS

Two Miocene rhinoceros (Teleoceros spp.) assemblages in Decatur County, Kansas, were compared in terms of taphonomy and depositional environments. The two assemblages, A and B, are 109.2 meters apart, separated by a valley, and each is situated at the base of a caliche paleosol. Microstratigraphic analysis indicates the two assemblages were part of the same partially lithified horizon, even though they are slightly different in elevation. Paleoenvironmental analysis suggests the assemblages accumulated in a distal floodplain environment. Quantification of the fossil specimens provided Mininum Number of Individuals (MNI) values of eight rhinoceros individuals at assemblage A and three at assemblage B. Taphonomic analysis and age-frequency distribution histograms reveal attritional demise with obvious predation. Both assemblages have a high proportion of Voorhies' Group I specimens in moderate to good condition, although assemblage B contained more complete and articulated remains than assemblage A. Paleocurrent analysis of assemblage A indicates a dominant flow direction for Group I and I-II specimens, with Group II-III and Group III specimens perpendicular to this. Assemblage B shows no preferred orientation. The degree of bone weathering was difficult to ascertain due to poor permineralization. However, plastic deformation from steady overburden pressure was obvious in some of the specimens from assemblage A. Anomalous p1-p3 lengths and tusk shapes occurred in all individuals from assembage B, and this may invite reevaluation of Teleoceros systematics. Assemblages A and B are taphonomically related, but assemblage A likely experienced more transport, and the more elevated assemblage B accumulated closer to the original (primary) thanatocoenose.