Monday, September 15, 2014

Lakukullus anatisrostratus: a new Miocene Neogene Nothrotheriid Sloth From Bolivia

Lakukullus anatisrostratus, gen. et sp. nov., a new massive nothrotheriid sloth (Xenarthra, Pilosa) from the middle Miocene of Bolivia

Authors:

Pujos et al

Abstract:

Xenarthra constitute one of the most representative groups of South American endemic mammals. The armored Cingulata is recorded beginning in the Itaboraian SALMA (lower Eocene; Pujos et al., 2012). Its sister group is Pilosa, which includes Tardigrada, the sloths, and Vermilingua, the South American anteaters.

Sloths appear during the Eocene–Oligocene transition (Tinguirirican SALMA) in Chile, represented by Pseudoglyptodon (McKenna et al., 2006). The late Oligocene Deseadan SALMA saw the emergence of Mylodontidae (e.g., Octodontotherium and Orophodon) and Megalonychidae (e.g., Deseadognathus) in Patagonia and the Bolivian altiplano (Pujos et al., 2007). Megatherioidea appear later during the middle Miocene, Megatheriidae in the Santacrucian SALMA (i.e., Megathericulus; Pujos et al., 2013), and Nothrotheriidae in the Huayquerian SALMA (i.e., Mionothropus; De Iuliis et al., 2011). According to De Iuliis et al. (2011), Nothrotheriidae is supported by 13 unequivocal synapomorphies and includes at least five genera: Mionothropus, Pronothrotherium, Thalassocnus, Nothrotherium, and Nothrotheriops. Several possible nothrotheriids, generally represented by poor material, have been described from Colombia (Huilabradys), Argentina (e.g., Nothropus, Chasicobradys, Amphibradys, and Xyophorus), and Bolivia (Xyophorus and Hiskatherium). Those from Argentina are poorly diagnosed, cannot certainly be differentiated morphologically from other taxa such as Hapalops, and are likely invalid. Nothropus priscus is exclusive to the Pleistocene of Argentina and is not present in the Amazon (see De Iuliis et al., 2011, for further details). By its central geographical position in South America, the present territory of Bolivia (Fig. 1) has played an important role in the evolution and diversity of mammals during the Paleogene and Neogene periods (Croft, 2007), although few nothrotheriids have been recorded from this country. St.-Andr e (1996) assigned a dentary and an astragalus to Xyophorus villarroeli from the Huayquerian SALMA of Achiri; previously this genus was known from the Santacrucian (Ameghino, 1887, 1891, 1894) and Chasicoan of Argentina with X. bondesioi (Scillato-Yan e, 1979). A partial skull and mandible of X. villarroeli is also recorded from the Laventan SALMA of Quebrada Honda (D Hapalops angustipalatus Frailey, 1988; Fig. 3 A–D; see Scillato-Yan e and Carlini, 1999, for further details), which also yielded the dentary of the peculiar Megatherioidea Hiskatherium saintandrei, recently described by Pujos et al. (2011). Croft et al. (2009) noted the presence of Xyophorus cf. bondesioi in the Friasian SALMA of Cerdas.

The Laventan SALMA Quebrada Honda vertebrate locality was identified by Hoffstetter (1977). Croft (2007) presented the most recent list of the vertebrate fauna, which includes the marsupials Didelphimorphia, Paucituberculata, and Sparassodonta, native ungulates Litopterna, Notoungulata, and Astrapotheria, five rodent clades (Dasyproctidae, Eocardiidae, Octodontidae, Echimyidae, and Chinchillidae), and xenarthrans, represented by dasypodids, glyptodontids, and sloths. Three sloths have previously been reported from Quebrada Honda: the nothrotheriid Xyophorus villarroeli, the megatherioid Hiskatherium saintandrei, and a mylodontid indet. (Takai et al., 1984). Here we describe the fourth sloth, a massive Nothrotheriidae.

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