Eremotherium Laurillardi (Lund) (Xenarthra, Megatheriidae), the Panamerican giant ground sloth: Taxonomic aspects of the ontogeny of skull and dentition

Synopsis

For most of the past 150 years the presence of only giant megatheriine ground sloths in the Pleistocene of Brazil has been recognised. However, it has recently been claimed that a dwarf Eremotherium species was present sympatrically with the large‐sized giant ground sloth in northeastern and southeastern Brazil during the late Pleistocene and that the concept of a single Panamerican species was improbable. Based on analysis of the ontological sequence of skull suture closure and dental development of remains from a single locality, we demonstrate that the ‘dwarf’ species is based on the remains of immature individuals, at very early ontogenetic stages, of the large‐sized species. Further, we reaffirm that the most parsimonious hypothesis is to consider all large‐sized Eremotherium remains as belonging to a single species of Panamerican distribution.

Key words:

• Megatheriinae
• dwarf megathere
• systematics
• taxonomy
• palaeobiogeography