Paleobiological inferences on middle Eocene native ungulates from South America: Morphofunctional analysis of Notostylops and Notopithecus

VERA, BÁRBARA; MEDINA-GONZÁLEZ, PAUL; MORENO, KAREN

JOURNAL OF MORPHOLOGY

WILEY-LISS, DIV JOHN WILEY & SONS INC

Lugar: New York; Año: 2022

0362-2525

Eocene early-diverging representatives of South American extinct notungulates aretraditionally considered to have been ‘generalists’ and ‘non-specialized’ in terms ofappendicular skeleton and locomotor behavior, as is the case with the notostylopidNotostylops, a middle Eocene iconic taxon from Patagonia (Argentina). However, they aremainly known from dental remains, and associated cranial and postcranial elements arescarce. The discovery of a nearly complete specimen attributed to N. murinus allows us to: 1)increase the knowledge of the anatomy of its appendicular skeleton; 2) identify isolated bonesfrom several collections and suggest different taxonomic interpretations for publishedspecimens; 3) perform a biomechanical and functional study using morphofunctional spacesanalysis to infer its paleoecological attributes (e.g. posture, locomotor habit, estimated speedand body mass); and 4) establish morphofunctional comparisons, based on possiblefunctional ranges, with other extinct early-diverging notoungulates from the middle Eocene,such as the Notopithecid Notopithecus. Our evidence suggests that Notostylops was amedium-sized mammal (8.5 – 20 kg), which could achieve a dynamic digitigrade posture thatallowed a scansorial secondary locomotor habit and a speed of up to 50 km/h. WhileNotopithecus was a small-sized mammal (0.6 –1.4 kg) with a plantigrade posture both in astatic and dynamic context, terrestrial habits and speed of up to 35 km/h. Therefore, weconclude that these Eocene notoungulates show diverse locomotor capabilities, reflectedunder the morfofunctional spaces constructed, which can be associated to early nichediversifications, clearly contrasting with the ‘all-generalists’ paradigmatic view.