On the status of the giant mylodontine sloth Glossotherium wegneri (Spillmann, 1931) (Xenarthra, Folivora)from the late Pleistocene of Ecuador

Abstract

The late Pleistocene mylodontine sloth Glossotherium wegneri (Spillmann, 1931) (Interandean ­region, Ecuador) has been assigned to Glossotherium Owen, 1839 and Oreomylodon Hoffstetter, 1949 (the latter ranked as a subgenus or genus), and synonymized with G. robustum (Owen, 1842). However, the phylogenetic and comparative analyses conducted here, which include previously undescribed remains, strongly suggest specific distinction for G. wegneri and that there is little, if any, support for generic or subgeneric distinction for Oreomylodon. Among the notable features of this species are the ­presence of an internasal element, marked expansion of the rostrum anteriorly, and dorsoventrally and the palatal region transversely, increased separation of the caniniform tooth from the anterior edge of maxilla, increased relative braincase width, relatively enlarged hypoglossal foramen, and greatly elongated zygomatic process of the squamosal. The resulting single MPT recovered a monophyletic Glossotherium, with the following phylogenetic arrangement of the species of this genus (G. robustum + ((G. wegneri + G. tropicorum Hoffstetter, 1952) + (G. phoenesis Cartelle, De Iuliis, Boscaini & Pujos, 2019 + G. tarijense Ameghino, 1902))).

Postcranial anatomy of the extinct terrestrial slothSimomylodon uccasamamensis(Xenarthra, Mylodontidae) from the Pliocene of the Bolivian Altiplano, and its evolutionary implications

“…In these latter taxa, the proximal and posterior borders of the ulna meet at an almost orthogonal angle (Webb 1989; De Iuliis et al . 2020), a feature also observed in Scelidotherium and Catonyx (McDonald 1987; Boscaini et al . 2019a, char.…”

“…The olecranon meets the posterior edge of the ulna at a wide angle, similar to the condition in all Mylodontinae with the exception of Thinobadistes segnis (Webb 1989) and Glossotherium wegneri (De Iuliis et al . 2020). In these latter taxa, the proximal and posterior borders of the ulna meet at an almost orthogonal angle (Webb 1989; De Iuliis et al .…”

“…wegneri (De Iuliis et al . 2020). However, the proportions of the distal articulation of the radius do not vary conspicuously in mylodontids (Boscaini et al .…”

New well-preserved materials ofGlossotherium chapadmalense(Xenarthra, Mylodontidae) from the Pliocene of Argentina shed light on the origin and evolution of the genus

“…2A, 3A), a pattern also observable in the holotype skull MACN Pv 8675. Similar conformations of the nasofrontal suture are observed in Glossotherium robustum, G. phoenesis, G. wegneri, and juvenile specimens of Lestodon armatus Gervais, 1855 (Esteban, 1996;Czerwonogora and Fariña, 2013;Cartelle et al 2019;Román-Carrión and Brambilla, 2019;De Iuliis et al, 2020). Other genera such as Mylodon, Paramylodon, and Simomylodon generally show a posteriorly pointed nasofrontal suture (Stock, 1925;Román-Carrión and Brambilla, 2019).…”

Xenarthrans of the collection of Santiago Roth from the Pampean Region of Argentina (Pleistocene), in Zurich, Switzerland

“…These cranial regions are frequently found in ground sloths, which led Brambilla and Ibarra ( 2018b ) to produce a study focused on the occiput. While occipital shape has been shown to be a complex character within mylodonts (see Boscaini et al, 2022 ; De Iuliis et al, 2020 ;), PIMUZ A/V 496 does not exhibit the occiput enlargement known in Gl. robustum compared to other sloths (Brambilla & Ibarra, 2018b ).…”