The oldest record of South American bats

TEJEDOR MF; CZAPLEWSKI N; GOIN FJ; ARAGÓN E

JOURNAL OF VERTEBRATE PALEONTOLOGY

SOC VERTEBRATE PALEONTOLOGY

Lugar: Lawrence; Año: 2005 vol. 25 p. 990 - 993

0272-4634

A new Paleogene mammal fauna was recently recovered in northwestern Chubut Province, Patagonia, Argentina. The mammal-bearing strata belong to the Middle Chubut River volcanic-pyroclastic complex (Fig. 1), of Paleocene-Eocene age (Aragón and Mazzoni, 1997). The site, named Laguna Fría, is about 50 km west of the town of Paso del Sapo, on the property of Estancia San Ramón (Fig. 1), and has produced hundreds of vertebrate fossils, especially mammals. Among the Laguna Fría taxa, there are several species referable to almost all the South American marsupial orders, including Peradectia (Peradectidae, Caroloameghiniidae), Sparassodonta (Borhyaenidae), Microbiotheria (Microbiotheriidae), Polydolopimorphia (Glasbiidae, Gashterniidae, Polydolopidae), Didelphimorphia (Protodidelphidae, Derorhynchidae, Sternbergiidae), and Paucituberculata (family indet.). Also, dasypodid xenarthrans are represented, as well as several orders of South American ?ungulates? such as ?condylarths,? litopterns, notopterns, notoungulates, and astrapotheres. However, a remarkable new occurrence is the oldest record ofbats for South America, described herein. The specimens are depositedin the paleontological collection of the LIEB (Laboratorio de Investigacionesen Evolución y Biodiversidad), Facultad de Ciencias Naturales, Sede Esquel, Universidad Nacional de la Patagonia ?San Juan Bosco?. Geochronological data taken from nearby volcanic deposits indicate that the fauna is not younger than Early Eocene age. Alkaline basalts exposed southeast of Laguna Fría, which are related to the alkaline basalts (Andesitas Huancache) that overly the fossiliferous level, have given Ar40/Ar39 dates of 52 Ma (Alric, 1997). Also, a K/Ar age was obtained from a sample of whole rock of the underlying Barda Colorada ignimbrite, giving an age of 58.6 Ma (Archangelsky, 1974, corrected with 1978 constants). Thus, the Laguna Fría vertebrate fossils are presentlybracketed by dates of 58.6 and 52 Ma.