New titanosaurian sauropod tracks with exceptionally well-preserved claw impressions from the Upper Cretaceous of Argentina

Abstract

A new titanosaur sauropod ichnotaxon named Teratopodus malarguensis gen. et sp. nov is erected based on a unique association of ten characters. It is represented by new tracks discovered in the upper section of Anacleto Formation outcropping in southern Mendoza province (middle Campanian, Neuquén Basin, Argentina). Teratopodus diagnosis includes suboval-shaped pes tracks, with a slightly obtuse V-shaped heel (PLM° = 95°–100°) and three large, laterally deflected claw impressions corresponding to digits I, II and III, and symmetrical kidney-shaped manus tracks with a slightly concave posterior border. Teratopodus has a medium-gauge trackway and a medium degree of heteropody (~1/3). In addition, a new characterization of heel impressions in sauropod tracks is herein proposed taking into account a distinction between ‘V-shaped’ and ‘U-shaped’ heel impression morphology and the ‘postero lateral-medial angle’ (PLM°). The trackmakers are two titanosaurs specimens of a relatively small-medium size of ca. 11 m and 14 m in length. These tracks are preserved in poorly drained floodplain deposits with ephemeral channels controlled by flash flood episodes. In this context, the trackmakers walked from a humid ground to a more flooded one, leaving behind one of the best-preserved sauropod pes tracks ever recorded in South America.