An original Lujanian Megatherioidea from Peru: implications concerning the locomotion of sloths

FRANÇOIS, PUJOS; GERARDO, DE IULIIS; LARS, WERDELIN; CHRISTINE, ARGOT

Boca Raton, Florida, Estados Unisdos

Congreso; 7th International Congress of Vertebrate Morphology; 2004

The Society of Vertebrate Morphology

    Lujanian localities from the coastal site Piedra Escrita and the Andean Cave Casa del Diablo have yielded three specimens of a new Tardigrada (Mammalia: Xenarthra). This original fossil sloth exhibits a peculiar mosaic of characters. Some of these are probably convergent (e.g., 5/4 quadrangular teeth, a formula characteristic of Megatheriidae), while others indicate arboreal capabilities, distinct from the suspensory locomotion of extant sloths. The arboreality of this sloth is suggested by poorly constrained elbow, hip, and ankle joints, a short olecranon and a convex posterior border of the ulna, good capacities of pronation-supination, a wide range of dorsiflexion at the wrist, and hook-shaped digits. This new taxon underscores the great diversity of locomotor modes that evolved in Tardigrada: an arboreal species is now added to the already known terrestrial, subarboreal and aquatic sloths. A preliminary phylogenetic analysis suggests that the evolutionary history of Megatherioidea has been influenced by locomotor adaptations.