Spalacotheriid ‘symmetrodonts’ from the Early Cretaceous of Spain

Abstract

ABSTRACTSpalacotheriids, basal trechnotheres with an acutely angled, reversed-triangle pattern of major molar cusps, are relatively rare pan-Laurasian mammals that ranged through much of the Cretaceous but are generally not well represented in the fossil record. Herein we describe newly collected specimens from the Molino Alto 1 locality, Teruel Province, Spain, and review previously described materials from the nearby locality of Galve; the sites lie in the same horizon in the upper El Castellar Formation and are of early Barremian age. On this basis, we recognize and name Aliaga molinensis, gen. et sp. nov., and provisionally place in the same genus a previously described species, cf. Aliaga henkeli, comb. nov., which appears to be the largest known spalacotheriid. The two species are characterized by a distinctive, multicuspate cingulid on lower cheek teeth. Based on acuteness of molar cusp triangulation and other features (e.g., planar molar shearing surfaces, elongation and cusp pattern of penultimate premolar, reduction of last molar, simplification of upper molar crown pattern), the species are referred to the Spalacolestinae. This subfamily is most diverse in North America, where it ranged from Albian–Campanian, but first appears in the Barremian of Western Europe, supporting the hypothesis that the group had a Eurasian origin and later dispersed to North America.