Small mammals (Insectivora, Lagomorpha, and Rodentia) from the early Pleistocene (Irvingtonian) Leisey Shell Pit Local Fauna, Hillsborough County, Florida

Abstract

Twelve species of small mammals, including one species of Insectivora, two species of Lagomorpha, and nine species of Rodentia, are reported from the early Pleistocene (early Irvingtonian) Leisey Shell Pit Local Fauna, Hillsborough County, Florida. Most taxa of small mammals are rare in the Leisey fauna. The most common species is the sigmodontine rodent Sigmodon libitinus, followed in abundance by the hydrochaerid Neochoerus sp., the arvicoline Pedomys sp., the soricid Blarina cf. B. carolinensis, the geomyid Geomys pinetis, the giant castorid Castoroides leiseyorum, the erethizontid Erethizon dorsatum, and the leporid Sylvilagus floridanus. Four undescribed species of rodents occur at Leisey, three of which, the arvicolines Pedomys and Synaptomys sp. and the large peromyscine Podomys sp., are represented by insufficient material for formal description. Castoroides leiseyorum is described as a new species that differs from the Rancholabrean C. ohioensis in the absence of a mesopterygoid fossa, but is similar to lhe latter in size and most other morphological characters. Biochronological analysis of the rodents and lagomorphs from Leisey indicates a late early Irvingtonian age, probably between 1.3 and 1.0 Ma. C. leiseyorum, S. libitinus, and the undescribed species of Pedomys, Synaptomys, and Podomys are known only from Florida late early Irvingtonian faunas. The records of S. floridanus, G. pinetis, and E. dorsatum from Leisey are among the oldest occurrences of these extant species. Other Florida small mammal faunas similar in age to Laisey are Haile 16A, Haile 21A, and Payne Creek Mine. Correlative early Irvingtonian faunas from western North America include: Gilliland, Texas; Holloman, Oklahoma; Kentuck and Wathena, Kansas; Sappa, Nebraska; and Java, South Dakota.