Palaeoproteomics resolves sloth relationships

Abstract

The living tree sloths Choloepus and Bradypus are the only remaining members of Folivora, a major xenarthran radiation that occupied a wide range of habitats in many parts of the western hemisphere during the Cenozoic, including both continents and the West Indies. Ancient DNA evidence has played only a minor role in folivoran systematics, as most sloths lived in places not conducive to genomic preservation. Here we utilise collagen sequence information, both separately and in combination with published mtDNA evidence, to assess the relationships of tree sloths and their extinct relatives. Results from phylogenetic analysis of these datasets differ substantially from morphology-based concepts: Choloepus groups with Mylodontidae, not 64 Megalonychidae; Bradypus and Megalonyx pair together as megatherioids, while monophyletic Antillean sloths may be sister to all other folivorans. Divergence estimates are consistent with fossil evidence for mid-Cenozoic presence of sloths in the West Indies and an early Miocene radiation in South America. The sloths (Xenarthra, Folivora), nowadays a taxonomically narrow (6 species in 2 genera) component of the fauna of South and Central America 1,2 were once a highly successful clade of placental mammals as measured by higher-level diversity (Fig. 1). Diverging sometime in the Palaeogene from their closest relatives, the anteaters (Vermilingua), folivorans greatly expanded their diversity and range, eventually reaching North America as well as the West Indies 3-8. During the late Cenozoic sloth lineage diversity may have expanded and contracted several times 9. Final collapse occurred in the late Quaternary (end-Pleistocene on the continents, mid

New mammalian and avian records from the late Eocene La Meseta and Submeseta formations of Seymour Island, Antarctica

“…Therefore, the newly described metacarpal is either further evidence, or new evidence, that Xenarthra was indeed present on Antarctica during the Eocene depending upon one's stance with regard to prior controversies. This record is consistent with the estimated timing of origin for Folivora by the early Eocene, and of Xenarthra in the Paleocene (e.g., Presslee et al, 2019).…”

“…Xenarthra is proposed to have originated in South America, and thus is plausibly anticipated in the Paleogene of Antarctica given inferred land connections between these continents during the early Cenozoic (Woodburne & Case, 1996;Delsuc et al, 2019;Presslee et al, 2019). The new metacarpal extends the known Paleogene geographic range of Xenarthra into Antarctica.…”

The earliest record of Caribbean frogs: a fossil coquí from Puerto Rico

“…Lett. 16: 20190947 molecular evidence is consistent with the synchronous arrival of terrestrial organisms to the region approximately 33.9 ± 1 Ma, while others clearly arrived through multiple overwater dispersal events throughout the Neogene or even earlier [8,13,15,35,36,[44][45][46][47][48][49][50]. Furthermore, molecular phylogenetic studies have suggested a similar Oligocene arrival for at least some anuran taxa on the Puerto Rican and Hispaniolan banks, such as Leptodactylus [13] and Peltophryne [15].…”

Early Oligocene chinchilloid caviomorphs from Puerto Rico and the initial rodent colonization of the West Indies

“…However, these results are preliminary inasmuch as the proposed position of Borikenomys is likely to evolve with additional morphological data. If this phylogenetic link is confirmed, these endemic giant Caribbean rodents could have a remarkable antiquity on the islands (as for Caribbean sloths [27,28] and coquí frogs [75]) and thus could represent a unique case of long-lived insular rodent lineage. Alternatively, these Oligocene Puerto Rican chinchilloids could have become extinct without descendants.…”