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

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