The dentary of Protolipterna ellipsodontoides: description, taxonomy, and palaeobiology

Abstract

ABSTRACT Protolipterna ellipsodontoides is a small bunodont South American native ungulate, generally considered an early litoptern, exclusively found in the Palaeogene Itaboraí Basin. Its dentition is well known; however, its mandibular morphology was only known by fragmentary materials. Here, we describe the first complete mandible of this species. A micro-CT scan reveals the first case of alveolus resorption in this putative early litoptern. Two accessory canals on the retromolar region are also described. Canals on the retromolar region are documented for other mammalian orders; however, this represents the first description of this feature for the Protolipternidae. Unlike more advanced litopterns, this species lacks specialisations related to strict herbivory, and its dental and mandibular morphology suggests an omnivore habit. A comparison with the mandible of another Itaboraian protolipternid, Miguelsoria parayirunhor, indicates the presence of different dietary specialisations. Body mass estimations for both species are also provided.