It is thought that sloths arrived in the Caribbean from South America (where they arose) around the Eocene-Oligocene boundary about 33 million years ago, when there was a significant sea level drop caused by a glaciation episode.[5] This has been associated with the GAARlandia (Greater Aves Antilles Ridge) hypothesis, where the Aves Ridge is suggested to have formed a land bridge during the interval, allowing overland migration into the Greater Antilles. The existence of such a land bridge has been questioned because of the lack of geological evidence for the Aves Ridge having been subaerially exposed[6] as well as the fact that many other South American animals (such as marsupials and ungulates) are absent from the Greater Antilles, making a complete land bridge unlikely.[7][4][note 1] The earliest evidence suggesting the presence of sloths in the Caribbean is a partial femur from the Early Oligocene of Puerto Rico.[8] Other pre-Pleistocene fossil remains include Imagocnus from the Early Miocene of Cuba,[9] and an indeterminate species from the Late Miocene of the Dominican Republic.[10]
Description
Megalocnid sloths were relatively small compared to mainland ground sloths,[11] though they were the largest mammals native to the Caribbean islands[4] with the largest species Megalocnus rodens estimated to weigh around 146 kilograms (322 lb)[11] or 270 kilograms (600 lb),[4] with the smallest genera Neocnus and Acratocnus estimated to only weigh 8–15 kilograms (18–33 lb). [11]
Ecology
Like other sloths megalocnids were probably folivores, with some authors suggesting that based on the anatomy of their limbs, that Neocnus and Acratocnus were likely climbing animals.[11]
The taxonomy of Caribbean sloths is in flux, with the number of species present among the Pleistocene-Holocene taxa in question; some species are likely junior synonyms, while the diversity of some genera is probably understated.[12] The mitochondrial DNA study suggests that Acratocnus ye and Parocnus serus are deeply divergent from each other, having split during the Oligocene, suggesting an early radiation within the group. An alternative taxonomy of the group has been proposed including the families Acratocnidae and Parocnidae within a new superfamily, Megalocnoidea.[1]
Based on White and MacPhee (2001):[13] and Vinola-Lopez et al. 2022[10]
Sloths in the Caribbean survived about 5,000 years longer than ground sloths on the mainland. On Cuba the latest date for Megalocnus is calibrated 4700 years Before Present (BP). approximately 2700 BC.[15] while dates for Parocnus browni are around 6250 BP (4250 BC). On Hispaniola the dates for some indeterminate sloth specimens are around 5000 BP (3000 BC); these dates roughly coincide with the first settlement of the Caribbean, which suggests that humans were the cause of the extinction.[16] Remains of Caribbean sloths have been found in a number of archaeological sites suggesting that they may have been consumed by the earliest inhabitants of the Caribbean, although evidence of hunting is inconclusive.[17]
^Houben, A.J.P.; van Mourik, C.A.; Montanari, A.; Coccioni, R.; Brinkhuis, H. (June 2012). "The Eocene–Oligocene transition: Changes in sea level, temperature or both?". Palaeogeography, Palaeoclimatology, Palaeoecology. 335–336: 75–83. Bibcode:2012PPP...335...75H. doi:10.1016/j.palaeo.2011.04.008.
^Ali, Jason R. (March 2012). "Colonizing the Caribbean: is the GAARlandia land-bridge hypothesis gaining a foothold?: Commentary". Journal of Biogeography. 39 (3): 431–433. doi:10.1111/j.1365-2699.2011.02674.x. S2CID84576035.
^MacPhee, R.D.E.; Iturralde-Vinent, M.A. (1995). "Origin of the Greater Antillean land mammal fauna, 1: New Tertiary fossils from Cuba and Puerto Rico". American Museum Novitates (3141): 1–31. hdl:2246/3657.
^MacPhee, R. D. E.; Iturralde-Vinent, M. A.; Vázquez, Osvaldo Jiménez (January 2007). "Prehistoric Sloth Extinctions in Cuba: Implications of a New "Last" Appearance Date". Caribbean Journal of Science. 43 (1): 94–98. doi:10.18475/cjos.v43i1.a9. ISSN0008-6452. S2CID56003217.
