THE CINGULATA (MAMMALIA, XENARTHRA) OF THE FRAY BENTOS FORMATION (LATE OLIGOCENE) OF URUGUAY

BOSTELMANN, ENRIQUE; CIANCIO, MARTÍN R.; RINDERKNECHT, ANDRÉS; PEREA, DANIEL

San Juan

Congreso; IV Congreso Latinoamericano de Paleontologia de Vertebrados; 2011

Museo de Ciencias Naturales - Univ. Nac. de San Juan

Late Oligocene South American fossil faunas from middle latitudes are extremely scarce. In Uruguay, this temporal interval is represented by the Fray Bentos Formation, with two well-known fossiliferous localities: the Nueva Palmira area, and the Santa Lucia river basin. Local facies include sub-aerial and fluvial deposits, with diverse well formed paleosols, and calcretes (Tófalo and Morrás, 2009). The fossil mammal assemblages collected from these deposits suggest correlation with the late Oligocene Deseadan SALMA of Patagonia (Ubilla et al. 2004). Since Kraglievich´s (1928) first report of a fossil cingulate on his “Piso Palmirense”, only a handful subsequent studies have referred to the specimens collected in the Nueva Palmira and the Santa Lucia River localities. In this communication we present an updated review of the history and taxonomy of all known remains of Paleogene cingulates collected in Uruguay. Glyptodonts are represented at the Santa Lucia river basin by three isolated osteoderms assignable to the Glyptatelinae, cf. Glyptatelus (Ameghino, 1897). Of special interest is the mobile osteoderm, previously referred by Perea (1993) to a eutatine armadillo. At the Barrancas de Nueva Palmira, a set of ten “rosette”-patterned osteoderms, in which a sub-circular central figure is surrounded by numerous small peripheral ones, can be assigned to the Glyptodontidae incertae sedis. Three postcranial remains were associated with these osteoderms. The armadillos are represented by two different genera of Euphractinae Euphractinii. The first one is a large-bodied form, probably representing a new genus and species, and closely allied to the Miocene genus Vetelia, Ameghino, 1891. The isolated osteoderms belonging to this taxa represents the most abundant cingulate remains of the Uruguayan Paleogene. Different sets of osteoderms have been collected from five localities around the Nueva Palmira basin, and a small specimen (hesitantly referred to this taxon) also comes from the Santa Lucia River. Typically, the osteoderms are rectangular and thick, with a smooth, punctuated, external surface. The sculptures include an “anchor shape” central figure that does not extend to the posterior margin, surrounded antero-laterally by trapezoidal figures. The peculiar piliferous system consists of two large, circular foramina, located in the posterior border, coupled with numerous small foramina along the lateral and posterior margins of the osteoderms. The second armadillo genus is known from small, associated osteoderms; these remains appear more derived than the typical Deseadan species known from Patagonia. Finally, a set of fragmentary remains of a small cingulate from the Santa Lucia River is tentatively referred to the Peltephilidae incertae sedis. Comparisons with other late Oligocene faunas from Bolivia and Argentina are briefly discussed.