Taxonomy, paleoecology and taphonomy of ground sloths (Xenarthra) from the Fairmead Landfill locality (Pleistocene: Irvingtonian) of Madera County, California

article i nfo Article history: Received 26 October 2011 Available online 3 December 2012 The Fairmead Landfill locality contains a diverse middle Irvingtonian, (0.78-0.55 Ma), vertebrate fauna that in- cludes three sloths, Megalonyx wheatleyi, Nothrotheriops shastensis and Paramylodon harlani. The co-occurrence of these three genera in a single fauna is relatively rare in both the Irvingtonian and Rancholabrean and this is onlythe fourth documentedIrvingtonian fauna tocontain all three slothgenera. The presence ofthe threediffer- ent sloths, each of which had different ecological requirements, indicates the presence of a variety of different habitats at this time and a heterogeneous landscape. Preliminary analysis of pollen from the site supports the interpretation of the existence of a mosaic of plant communities, but a landscape dominated by a mesic grass- land. This interpretation is also supported by the total faunal diversity that includes taxa associated with wood- lands as well as open habitat and taphonomic differences in the preservation and relative abundance of the different sloths. Evolutionarily the Fairmead Landfill sloths show a suite of morphological, size and proportional characters that indicate they represent transitional populations between older and younger members of their respective lineages.