FOSSIL BATS OF THE AMERICAS
late Oligocene, Arikareean NALMA
The Brooksville 2 site was discovered in 1994 in a limestone quarry about 10 km northeast of Brooksville in Hernando County in central Florida. The site consists of clays and sands filling karst solution features in marine Oligocene limestone. The fossils were collected mostly by screenwashing because of the abundance of microvertebrates and the rarity of larger mammals (Hayes 2000). The vertebrate fauna includes frogs, lizards, snakes, and a diverse sample of mammals. Hayes (2000) studied the Brooksville marsupials, insectivores, lagomorphs, rodents, and carnivores. Mammals of medium to large body size include: the horse (Miohippus), two small artiodactyls (Nanotragulus and the camelid Nothokemas), and six species of small carnivores (three mustelids and three canids). Besides bats, the small mammal fauna consists of a didelphid marsupial (Herpetotherium), two insectivores (the erinaceid Parvericius and Centetodon), one lagomorph (Megalagus), and at least three rodents (the castorid Agnotocastor, the heteromyid Proheteromys, and an entoptychine).
The maximum age of Brooksville 2 (Hayes 2000) is constrained by the presence of the erinaceid insectivore Parvericius and entoptychine rodents, both of which appear at the beginning of the late early or medial Arikareean (=Ar2; ~28 Ma; Tedford et al. 1996). The minimum age is limited by the occurrence of Centetodon, Megalagus, Agnotocastor, and Miohippus, all of which go extinct at the end of the early Arikareean (~24 Ma). The artiodactyls Nanotragulus loomisi and Nothokemas waldropi are characteristic of early Arikareean faunas. Hayes (2000) placed the Brooksville 2 LF in the late early Arikareean (Ar2, 24-28 Ma). The similarity between the bat faunas from Brooksville 2 and I-75 indicates that these two faunas are not more than several million years apart in age, suggesting placement of Brooksville 2 early in the Ar2 (~26-28 Ma).
The chiropteran sample from Brooksville 2 consists of about 200 fossils representing five species, including mandible and maxilla fragments with teeth, isolated teeth, and limb bones. The Brooksville bat fauna includes a new genus and species of mormoopid, two undescribed species (one large, one small) representing a new genus of emballonurid, a large undescribed genus and species that may be a phyllostomid, and a single tooth of a molossid. Brooksville shares the first four of these species with I-75. The new genus of possible phyllostomid is also represented by a smaller species at I-75. After Thomas Farm, Brooksville 2 has the second largest bat sample from any North American Tertiary site. The Brooksville and I-75 bat faunas are very similar; both are dominated by the same species of mormoopid and large emballonurid.