Taphonomy of the terrestrial mammals of Leisey Shell Pit 1A, Hillsborough County, Florida

Abstract

The terrestrial mammal fraction of the Leisey Shell Pit 1A bone assemblage (early Pleistocene) is numerically dominated by medium-sized herbivores, with camelids and equids accounting for 45% and 22% of the individuals, respectively. Some taphonomic modifications to the bone assemblage look place at the site of deposition (scratchmarks, breakage, hydrodynamic sorting, and a limited amount of scattering); others occurred elsewhere, either in a nearby terrestrial setting (carnivore/scavenger activity, subaerial weathering both generally to a relatively low degree) or during fluvial transport to the site. There is no preferred orientation of the long bones at the site, suggesting the lack of a strong, directional current However, multidirectional tidal currents probably aided in carcass disassociation and winnowing of smaller, lighter elements. A significantly greater proportion of equid and proboscidean skeletal elements were weathered and damaged by mammalian carnivores than those of the camelids. Elements of the latter more frequently entered the site in an unmodified state as parts of carcasses (later disassociated) while those of the former were more often brought to the site individually in a modified condition. Population dynamics of Palaeolama mirifica and Equus "leidyi" (the two most common mammals) also conform to a mixture of catastrophic and attritional mortality. The principal mammalian carnivores responsible f6r modifying the Leisey bone assemblage were Canis armbrusteri and Arctodus pristinus. The former caused the bite marks and chewed surfaces on the bones of medium-sized herbivores, while the latter scavenged on the carcasses of ground sloths and proboscideans.