'First' appearances in the Cenozoic land-mammal record of the Greater Antilles: significance and comparison with South American and Antarctic records

Aim Through analysis of fossil records, the aim of this paper is to show that fossil representatives of at least three land-mammal clades (pitheciine atelid primates, heteropsomyine echimyid rodents, and megalonychid phyllophagan xenarthrans) that once lived in the Greater Antilles are as old as, if not older than, 'first' occurrences of these same groups on the South American mainland. Location Greater Antilles, South America, Antarctic Peninsula. Methods Analysis of Cenozoic land-mammal fossil records for the three areas. Results Comparison reveals an interesting similarity to the Tertiary vertebrate palaeontological record for the Antarctic Peninsula (Seymour Island), in the sense that the latter also includes early (Eocene) representatives of some typical 'South American' groups (e.g. meridiungulates, sloths, certain marsupial groups). Conclusions Given how limited the Antillean and Antarctic records are in quantity and quality, it seems unlikely that these 'first' appearances have much bearing on real origins (basal divergences). Rather, it suggests that the fossil basis for interpreting the origin and earliest diversification of 'South American' clades during the latest Cretaceous/early Cenozoic is probably even scantier than generally realized. In particular, the Antillean record strengthens arguments that some crown-group continental lineages are considerably older than fossil evidence currently allows - a point increasingly (if unevenly) supported by molecular studies of many of the same clades.