Reexamination of the Relationship of Pseudoprepotherium hoffstetter, 1961, to the Mylodont Ground Sloths (Xenarthra) from the Miocene of Northern South America

Abstract

We present a review of the Miocene mylodont sloths described from the Urumaco Formation, Venezuela, and the Villavieja Formation, Colombia, and reexamine their phylogenetic relationships to the holotype of Pseudoprepotherium from the Río Yuca Formation, Venezuela. Based on our analysis we propose a number of taxonomic changes and consider Pseudoprepotherium confusum to be sufficiently different from the type of Pseudoprepotherium venezuelanum, that it merits a distinct genus, Magdalenabradys. We include in this new genus post-cranial material formerly assigned to Bolivatherium urumaquensis as a new species, Magdalenabradys kolossiaia. Comparison of Mirandabradys, first described from the late Miocene, Urumaco Formation of Venezuela, and its included species with the holotype of Pseudoprepotherium indicates they are the same genus, and Mirandabradys is considered a junior synonym. Three species of Pseudoprepotherium are recognized: the genotypic species, P. venezuelanum from the Río Yuca Formation, P. socorrensis from the Socorro Formation and P. urumaquensis, from the Urumaco Formation. We propose that based on the poor preservation and incompleteness of the type material that Mirandabradys zabasi is not a valid species and should be considered a nomen dubium.