Neogene sloth assemblages ( M ammalia, P ilosa) of the C ocinetas B asin ( L a G uajira, C olombia): implications for the G reat A merican B iotic I nterchange

We describe sloth assemblages from the C ocinetas B asin ( L a G uajira peninsula, C olombia), found in the N eogene C astilletes and W are formations, located in northernmost S outh A merica, documenting otherwise poorly known biotas. The tentative referral of a specimen to a small megatherioid sloth, H yperleptus ?, from the early–middle M iocene C astilletes F ormation, suggests affinities of this fauna with the distant S anta C ruz F ormation and documents a large latitudinal distribution for this taxon. The late P liocene W are F ormation 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 I sthmus of P anama, and a few hundred thousand years older than the classically recognized first main pulse of the G reat A merican B iotic interchange ( GABI 1), the W are F ormation furthermore documents an important fauna for the understanding of this major event in N eogene palaeobiogeography. The sloths for which unambiguous affinities were recovered are not closely related to the early immigrants found in N orth A merica before GABI 1.