Neogene sloth assemblages (Mammalia,Pilosa) of theCocinetasBasin (LaGuajira,Colombia): implications for theGreatAmericanBioticInterchange

Abstract

We describe sloth assemblages from the Cocinetas Basin (La Guajira peninsula, Colombia), found in the Neogene Castilletes and Ware formations, located in northernmost South America, documenting otherwise poorly known biotas. The tentative referral of a specimen to a small megatherioid sloth, Hyperleptus?, from the early–middle Miocene Castilletes Formation, suggests affinities of this fauna with the distant Santa Cruz Formation and documents a large latitudinal distribution for this taxon. The late Pliocene Ware Formation is much more diverse, with five distinct taxa representing every family of ‘ground sloths’. This diversity is also remarkable at the ecological level, with sloths spanning over two orders of magnitude of body mass and probably having different feeding strategies. Being only a few hundred kilometres away from the Isthmus of Panama, and a few hundred thousand years older than the classically recognized first main pulse of the Great American Biotic interchange (GABI 1), the Ware Formation furthermore documents an important fauna for the understanding of this major event in Neogene palaeobiogeography. The sloths for which unambiguous affinities were recovered are not closely related to the early immigrants found in North America before GABI 1.

The Neogene Record of Northern South American Native Ungulates

“…The terrestrial mammalian fauna of the Castilletes Formation includes a sparassodont, a sloth, astrapotheres, litopterns, and notoungulates (Table 1; Amson et al, 2016;Suarez et al, 2016). The Castilletes Formation also records other terrestrial and marine fossils such as mollusks, echinoderms, arthropods, sharks, rays, bony fishes, snakes, turtles, crocodiles, cetaceans, and plants (Aguilera et al, 2013b;Cadena andJaramillo, 2015a, 2015b;Hendy et al, 2015;Moreno et al, 2015;Moreno-Bernal et al, 2016;Aguirre-Fernández et al, 2017a).…”

“…The Castilletes Formation also records other terrestrial and marine fossils such as mollusks, echinoderms, arthropods, sharks, rays, bony fishes, snakes, turtles, crocodiles, cetaceans, and plants (Aguilera et al, 2013b;Cadena andJaramillo, 2015a, 2015b;Hendy et al, 2015;Moreno et al, 2015;Moreno-Bernal et al, 2016;Aguirre-Fernández et al, 2017a). The mammalian fauna of the Ware Formation is characterized by an assemblage of sloths, cingulates, rodents, toxodontids, a procyonid, and a camelid (Table 1), the last two being immigrants from North America (Forasiepi et al, 2014;Moreno et al, 2015;Amson et al, 2016;Moreno-Bernal et al, 2016;Pérez et al, 2017). The Ware Formation also records crocodiles (Moreno-Bernal et al, 2016), turtles, bony fishes, fossil wood, and a diverse marine assemblage (Aguilera et al, 2013a;Hendy et al, 2015;Jaramillo et al, 2015;Moreno et al, 2015).…”

“…The taxa previously described for this assemblage are the sparassodont Lycopsis padillai (Suarez et al, 2016) and the megatherioid sloth Hyperleptus? (Amson et al, 2016). Althought the taxonomic status of Hyperleptus?…”

“…The mammalian fauna of the Ware Formation is characterized by a high diversity of herbivores (Figures 34, 35), which includes at least five different taxa of sloths (Amson et al, 2016), as well as cingulates, caviomorph rodents (Moreno et al, 2015;Pérez et al, 2016), a toxodont, a proterotheriid, and a camelid ( Table 1). The diversity and wide body mass range of herbivores from the Ware Formation suggest that they occupied different ecological niches, and that there was enough vegetation cover to sustain a complex herbivorous community.…”

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

“…In contrast to mylodontines, scelidotheriines were restricted to South America, and did not participate in the G.A.B.I. (Great American Biotic Interchange), as a probable consequence of their ecological restrictions due to specialized feeding habits (McDonald, 2005;Amson et al, 2016). During the Pleistocene, this clade was represented by three genera: (i) Valgipes, endemic to the intertropical region of Brazil (Cartelle et al, 2009(Cartelle et al, , 2019, (ii) Scelidotherium, from the Pampas region of Argentina and Uruguay (McDonald and De Iuliis, 2008;Corona et al, 2013), and (iii) Catonyx (=Scelidodon) a more widespread taxon known from Argentina, Bolivia, Brazil, Chile, Ecuador, Peru, and Uruguay (Miño-Boilini, 2016).…”