A reappraisal of the phylogeny of Mylodontidae (Mammalia, Xenarthra) and the divergence of mylodontine and lestodontine sloths

Abstract

The phylogeny of mylodontid sloths has recently been the subject of multiple studies. Contrasting hypotheses have been proposed, especially for the relationships among late Miocene–Pleistocene mylodontines and lestodontines. In this paper, a new and detailed phylogenetic analysis is conducted, after adding new characters and taxa previously unexplored from a phylogenetic point of view. New features derived from postcranial skeletal anatomy are added to previous studies based on craniodental evidence. In this way, the current reappraisal represents the first exhaustive phylogenetic study on the Mylodontidae that incorporates features coded for the entire skeleton. When available, multiple specimens of each bony element are observed for each operational taxonomic unit, in order to take into account intraspecific variation. The taxonomic sample of this study considers Mylodontinae at the specific level. However, many other Mylodontidae are considered, and their phylogenetic relationships tested. The taxonomic sample of this study is enriched with new taxa from central and northern South America, with the aim of compensating for the knowledge bias in favour of austral mylodontids, which have historically been more extensively studied than those from tropical latitudes. Special emphasis is given to the phylogenetic relationships of Mylodontinae, and particularly to the mylodontine and lestodontine sloths, that are recovered in the present study as monophyletic clades, and together form a larger monophyletic group. According to the present results, the Mylodontini–Lestodontini split occurred at the middle–late Miocene transition, giving rise to independent adaptive radiations across South and North America.

The first fossil skull of an anteater (Vermilingua, Myrmecophagidae) from northern South America, a taxonomic reassessment ofNeotamanduaand a discussion of the myrmecophagid diversification

“…Protamandua . The beginning of this diversification is approximately overlapped in time with the onset or development of similar events in other higher taxa in South America, such as the xenartrans Megatherioidea, Mylodontidae, Glyptodontidae and Dasypodini (Croft et al 2007; McDonald & De Iuliis 2008; Bargo et al 2012; Carlini et al 2014; Boscaini et al 2019), or the South American native ungulates Pachyrukhinae, Mesotheriinae and Toxodontidae related to Pericotoxodon and Mixotoxodon (Seoane et al 2017; Armella et al 2018a; Armella et al 2018b). This pattern shows the importance of the Early Miocene, particularly the Burdigalian, as a critical interval for the diversification of multiple South American land mammal lineages.…”

A Fossil Bone of a Giant Ground Sloth from the Last Millennium of the Pleistocene: New Data from Salto Department, Uruguay

“…According to the last phylogenetic study (Boscaini et al, 2019), it was a bulk-feeding mega-mammal, measuring ~4.5 meters from nose to tail tip ( Figure 2) and estimated to have weighed over 2 tons (Fariña et al, 2014). Remains of this kind of ground sloth were found in the Pleistocene deposits of Venezuela, Brazil, Bolivia, Paraguay, Argentina and Uruguay (Czerwonogora, 2010;Fariña et al, 2014), but some records date back to the Early Pliocene in Argentina (Deschamps et al, 2000).…”

Cranial Anatomy and Paleoneurology of the Extinct Sloth Catonyx tarijensis (Xenarthra, Mylodontidae) From the Late Pleistocene of Oruro, Southwestern Bolivia

“…By contrast, their fossil record is extremely rich and diverse, spanning chronologically from the late Eocene to the early Holocene, and geographically covering nearly all of the American supercontinent (e.g., McNab, 1985;Steadman et al, 2005;Gaudin and Croft, 2015). Mylodontidae is one of the most important folivoran clades, representing a major subdivision of sloths' diversity (e.g., Gaudin, 2004;Boscaini et al, 2019a;Delsuc et al, 2019;Presslee et al, 2019). Its representatives were mainly quadrupedal and terrestrial, and in some cases developed digging capabilities (e.g., Vizcaíno et al, 2001;Pujos et al, 2012).…”