Tuesday, June 21, 2016

[PaleoMammalogy • 2016] Aymaratherium jeani • A New Nothrotheriid Xenarthran from the early Pliocene of Pomata-Ayte (Bolivia): New Insights into the Caniniform–Molariform Transition in Sloths

Aymaratherium jeani  
Pujos, De Iuliis, Quispe, Adnet, Flores, Billet, Fernandez-Monescillo, Marivaux,
Münch, Prámparo & Antoine, 2016
   DOI:  10.1111/zoj.12429 

Tardigrade xenarthrans are today represented only by the two tree sloth genera Bradypus and Choloepus, which inhabit the Neotropical rainforests and are characterized by their slowness and suspensory locomotion. Sloths have been recognized in South America since the early Oligocene. This monophyletic group is represented by five clade straditionally recognized as families: Bradypodidae, Megalonychidae, Mylodontidae (†), Megatheriidae (†) and Nothrotheriidae (†). A new nothrotheriid ground sloth represented by a dentary and several postcranial elements, Aymaratherium jeani gen. nov., sp. nov., from the early Pliocene locality of Pomata-Ayte (Bolivia) is reported.This small- to medium-sized species is characterized especially by its dentition and several postcranial features. It exhibits several convergences with the ‘aquatic’ nothrotheriid sloth Thalassocnus and the giant megatheriid ground sloth Megatherium (M.) americanum, and is interpreted as a selective feeder, with good pronation and supinationmovements. The tricuspid caniniform teeth of Aymaratherium may represent a transitional stage between the caniniform anterior teeth of basal megatherioids and basal nothrotheriids (1/1C-4/3M as in Hapalops or Mionothropus) and the molariform anterior teeth of megatheriids (5/4M, e.g. Megatherium). To highlight the phylogenetic position of this new taxon among nothrotheriid sloths, we performed a cladistic assessment of the available dental and postcranial evidence. Our results, derived from a TNT treatment of a data matrix largely based on a published phylogenetic data set, indicate that Aymaratherium is either sister taxon to Mionothropus or sister to the clade Nothrotheriini within Nothrotheriinae. They further support the monophyly of both the Nothrotheriinae and the Nothrotheriini, as suggested previously by several authors.

ADDITIONAL KEYWORDS: Anatomy; Bolivia; early Pliocene; Nothrotheriidae; phylogeny; Pilosa; Xenarthra.




 Etymology. In reference to the Aymara (Aymar aru), a native ethnic group and language from the Andes, from where the specimens were recovered; and,the specific epithet for Jean Joinville Vacher (successively Director of the French Institute of Andean Studies – IFEA, Advisor of the Institute for Development Research – IRD in Bolivia, Advisor of Regional Cooperation for Andean Countries of the French Embassy during 2000/2012, and currently Assistant to General Executive Officer for Science of the IRD) for his friendship and constant support forpalaeontological investigations over the years.

 Francois Pujos, Gerry De Iuliis, Bernardino Mamani Quispe, Sylvain Adnet, Ruben Andrade Flores, Guillaume Billet, Marcos Fernandez-Monescillo, Laurent Marivaux, Philippe Münch, Mercedes B. Prámparo and Pierre-Olivier Antoine. 2016. A New Nothrotheriid Xenarthran from the early Pliocene of Pomata-Ayte (Bolivia): New Insights into the Caniniform–Molariform Transition in Sloths. Zoological Journal of the Linnean Society.   DOI:  10.1111/zoj.12429 

Figure 10. Hypothetical life reconstruction of Aymaratherium jeani gen. nov., sp. nov.
by Jorge Gonzalez.