Paleontology and Geochronology of the Deseadan (late Oligocene) of Moquegua, Perú

Abstract

Subsequent to our initial reports of the discovery of Deseadan fossils in southern Perú , we have obtained new data regarding the paleontology and geology of the upper member of the Moquegua Formation. These data include newly recovered fossil specimens and further analyses of those collected in our earlier field seasons. We have also obtained an ash directly from within the fossilbearing units near the summit of Cerro Pan de Azú car. Biotites from this Sugarloaf ash give an age estimate of 26.25 6 0.10 Ma, thus supporting our previous suggestion that these fossil-bearing horizons are of late Oligocene age (Deseadan South American Land Mammal ''Age'') and removing our query regarding a possible early Miocene age. Most of the fossils are of notoungulates and most of these are trachytheriine mesotheriids. Remarkably, three distinct mesotheriid taxa appear to have been present in the Moquegua fauna, none of which are referable to the common Trachytherus alloxus of the nearby and at least partly contemporaneous Salla beds of Bolivia. Other fossils documented here include postcranial elements of the notohippid notoungulate, Moqueguahippus, a macraucheniid litoptern (cf. Coniopternium), an osteoderm of an unnamed species of armadillo (Dasypodidae, cf. Dasypodinae), and a claw of a phorusrhacid bird. We also describe a diminutive new hystricognath rodent, Sallamys quispea, sp. nov. It is similar to, but distinct from, S. pascuali of Salla. Indeed, despite the temporal and geographic proximity of Moquegua to Salla, none of the taxa from Moquegua that can be identified to species are known from Salla. Likewise, we have failed to find any dasypodids from Salla that have osteoderms like that described in this work. Thus, it is appears that distinctive paleogeographic and

Late middle Eocene caviomorph rodents from Contamana, Peruvian Amazonia

“…On the dp4 of Cachiyacuy kummeli, Eobranisamys, Eoespina, Eosachacui, Eosallamys simpsoni, Sallamys pascuali, Sallamys cf. pascuali, and Branisamys (Hoffstetter and Lavocat, 1970;Lavocat, 1976;Frailey and Campbell, 2004;Shockey et al, 2009), the mesolophid is welldeveloped and labiolingually complete. On LACM 143451 (Eosallamys paulacoutoi; in Frailey and Campbell, 2004, p. 122), the mesolophid is reduced but appears as a well-defined cristulid still connected to the mesostylid.…”

“…On LACM 143451 (Eosallamys paulacoutoi; in Frailey and Campbell, 2004, p. 122), the mesolophid is reduced but appears as a well-defined cristulid still connected to the mesostylid. In Sallamys quispea Shockey et al, 2009, the mesolophid is reduced and includes two cristulids: one stemming from the mesostylid (neomesolophid) and the other from the ectolophid (true mesolophid). In Canaanimys maquiensis, the mesolophid on dp4 is reduced to a short cuspid-like cristid, like in MUSM 2651.…”

“…In addition, in having a posterior arm of the metaconid high and strongly connected to the mesostylid, the MUSM 2651 dp4 is somewhat peculiar among the Paleogene taxa known, since this character is otherwise found only in Cachiyacuy, Sallamys quispea and Sallamys cf. pascuali (Shockey et al, 2009). In Cachiyacuy, this character is rather variable and only found on some dp4s (MUSM 2663, 2670 [ Figure 4.5], 2669, and 2763-2765).…”

Two New Taxa (Caviomorpha, Rodentia) from the Early Oligocene Tinguiririca Fauna (Chile)

“…Deseadan caviomorphs are known from sequences in Patagonian Argentina (Ameghino, 1897(Ameghino, , 1902Loomis, 1914;Wood, 1949;Wood and Patterson, 1959;vucetich, 1989), Bolivia (Hoffstetter and Lavocat, 1970;Lavocat, 1976;Patterson and Wood, 1982;vucetich, 1989), Peru (Shockey et al, 2009), Uruguay (Kraglievich, 1932;Mones and Castiglione, 1979), Brazil (vucetich et al, 1994;vucetich and Ribeiro, 2003) and Chile (unpublished). In addition to Tinguiririca, preDeseadan caviomorphs are also now reported from the Santa Rosa and Contamana faunas of Peru (Frailey and Campbell, 2004;Antoine et al, 2011).…”

Nueva asociación de mamíferos del Paleógeno en el este de la Patagonia (provincia de Chubut, Argentina): implicancias biocronológicas y paleobiogeográficas

“…Los principales yacimientos paleontológicos portadores de fauna deseadense se localizan en Patagonia Argentina-Chubut, Santa Cruz (Marshall et al, 1983;Carlini et al, 2009) y en Bolivia -Salla (Marshall y Sempere, 1991), aunque también se registran en otras zonas de Argentina: Mendoza (Cerdeño, 2011), Entre Ríos y Corrientes (Bond et al, 1998 y referencias citadas allí); Brasil (Vucetich y Ribeiro, 2003), Uruguay (Ubilla et al, 1994), Chile y Perú (Shockey et al, 2009).…”