New insights on the quaternary fossil record of Isla de la Juventud, Cuba

Abstract

The fossil record of Isla de la Juventud, the second largest island in the Cuban archipelago, is very limited in the number of taxa and localities so far studied but can be key to further understand the biogeographical history and extinction of the fauna in the region. Here, we report the faunal assemblages of two recently discovered Quaternary deposits containing numerous vertebrates and land snails in northern Isla de la Juventud. The first locality, a marble breccia on the coast of Punta Bibijagua, contained remains of an extinct rodent and a sloth. The second locality, a dissolution fissure filled with fossil-bearing sediment in a marble quarry in Sierra de Casas, contained a rich assemblage of land snails and vertebrates. Nineteen species, 14 genera and nine families of gastropods were identified, of which 11 species and two genera are endemic. The snail fossil assemblage is similar to the community of living gastropods in the locality. Moreover, 12 taxa, four of them extinct, 11 genera from ten families of terrestrial vertebrates were recognized; including the first report of fossils frogs, toads, lizards, snakes, and tortoises from Isla de la Juventud. Because remains at Sierra de Casas were collected ex-situ, any possible stratigraphic relationship among them was lost, but we were able to determine the presence of at least two taphonomic modes that suggest different depositional histories. Furthermore, we found no evidence of extinction or extirpation among land snails in the region, but of the vertebrates’ assemblage two rodents, two sloths and a tortoise went extinct. These five taxa also disappeared in the mainland, suggesting that the extinction was in some cases taxonomic specific across the Cuban Archipelago.