FOSSIL BATS OF THE AMERICAS
A new genus and species of Mormoopidae from the Oligocene of Florida represents the first Tertiary fossil record of this family. This new mormoopid occurs in two Florida faunas, the Whitneyan I-75 LF and the early Arikareean Brooksville 2 LF. This mormoopid is the second most abundant bat in each of these faunas, represented by seven specimens from I-75 and 34 fossils from Brooksville 2. The new Florida Oligocene mormoopid is more similar to Mormoops than to Pteronotus in most characters, including: the large double-rooted p3; the absence of a groove separating the capitulum into medial and lateral portions on the distal humerus; the presence of prominent ridge on the distal humeral shaft; and the rounded extremity on the proximal radius. A systematic review of the Mormoopidae by Smith (1972) and a phylogenetic analysis of morphological characters by Simmons and Conway (2001) confirm that the two living genera in the Mormoopidae, Mormoops and Pteronotus, are each monophyletic, and form a monophyletic group (i.e., the family Mormoopidae) within the superfamily Noctilionoidea.
Prior to the discovery of the Florida Oligocene mormoopids, the oldest fossil of this family was a partial skeleton tentatively assigned to the living species Pteronotus parnellii from the early Pleistocene? (Irvingtonian? NALMA) of El Salvador in Central America (Webb and Perrigo 1984). Late Pleistocene fossils of mormoopids are known from Florida, the West Indies, Mexico, and Brazil (Morgan 1991; Morgan 2001; Arroyo-Cabrales 1992; Czaplewski and Cartelle 1998). There are eight living species in the Mormoopidae, two species of Mormoops and six species of Pteronotus, as well as one extinct species in each genus. All mormoopids are restricted to the Neotropical Region, with the exception of M. megalophylla which ranges into northern Mexico and the southwestern United States. Three extant mormoopids, M. blainvillii, P. macleayi, and P. quadridens, and two extinct late Pleistocene species, M. magna and P. pristinus, are endemic to the West Indies, although Morgan (1991) identified P. cf. P. pristinus from a late Pleistocene site in southern Florida. The other five species, M. megalophylla, P. davyi, P. gymnonotus, P. parnellii, and P. personatus are found on the Neotropical mainland from Mexico to South America. M. megalophylla (in late Pleistocene cave deposits), P. davyi, and P. parnellii also occur in the West Indies. The diversity and endemism of mormoopids in the West Indies suggests this group reached the Antilles early in their evolutionary history (Oligocene or Miocene). There are no endemic mormoopids in South America. Mormoopids occur primarily in the northern half of the continent, especially in the arid coastal regions of Colombia, Peru, and Venezuela where there are abundant caves (Smith 1972; Koopman 1982). The marginal distribution, lack of endemism, and absence of a Tertiary fossil record of mormoopids in South America suggests that this family may not have arrived in South America until after the Great American Biotic Interchange in the late Pliocene (~2.7 Ma).
All living species of mormoopids and natalids (see below) are obligate cave dwellers. In the West Indies, bats in these two families roost deep within large caves characterized by a stable microenvironment with high temperature and relative humidity (Goodwin 1970; Silva Taboada 1979). The roost ecology of both mormoopids and natalids strongly indicates that their present (and presumably past) distribution is limited by the availability of extensive cave systems (Morgan 2001).