Data from: Deciduous dentition and dental eruption sequence in Interatheriinae (Notoungulata, Interatheriidae): implications in the systematics of the group

Studies focused on deciduous dentition, ontogenetic series, and tooth eruption and replacement patterns in fossil mammals have lately increased due to the recognized taxonomic and phylogenetic weight of these aspects. A study of the deciduous and permanent dentition of Interatherium and Protypotherium (Interatheriinae) is presented, mainly based on unpublished materials. Deciduous cheek teeth are brachydont and placed covering the apex of the respective permanent tooth; in addition, some morphological and metrical differences are observed along the crown height. Five dental ontogenetic stages are distinguished among the juvenile specimens, based on the degree of wear, the replacement of the deciduous premolars, and the eruption of the molars. The crown height and the wear degree of different Interatheriinae taxa show: (1) eruption pattern of molars in an anterior-posterior direction (M/m1 to M/m3); (2) pattern of replacement of deciduous premolars and eruption of permanent premolars in a posterior-anterior direction (dP/dp4 to dP/dp2 and P/p4 to P/p2); and (3) eruption of M/m3 before the replacement of dP/dp4. Results allow evaluating the diagnostic dental characteristics used to describe some interatheriines, as well as reinterpreting some taxonomic assumptions: the holotype of Protypotherium diversidens is recognized as a juvenile of another species of the genus and the species is not validated, considering it as Protypotherium sp.; the holotype of Eudiastatus lingulatus falls in the variability of Protypotherium, becoming P. lingulatus, tentatively maintaining the species, and implying the synonymy between Eudiastatus and Protypotherium; and the holotype of Eopachyrucos ranchoverdensis is reinterpreted as bearing deciduous premolars