Anatomy of Eurotamandua joresi (Mammalia) from Grube Messel, Germany, based on computed tomography, and implications for its relationships. Part I: Background and forelimb

Abstract Micro-computed tomography of the unique skeleton of Eurotamandua joresi Storch, 1981 (middle Eocene, Grube Messel)—initially described as the oldest myrmecophagid and the only known Old World xenarthran—reveals details of its skeletal anatomy that were previously obscured, enabling close comparative study for the first time. In this report we focus on the forelimb. The segmentation of scapula, humerus, radius, ulna, carpals, metacarpals and phalanges reveals exceptional specializations for scratch digging. These include numerous features that are strikingly similar to those of palaeanodonts, and to a lesser degree manids, but which contrast sharply with those of the xenarthrans Tamandua and Dasypus . Other features once thought to ally Eurotamandua with xenarthrans, such as a secondary scapular spine, absence of teeth, and a tubular snout, are not restricted to Xenarthra. The new forelimb characters are here incorporated into a phylogenetic analysis that includes xenarthrans, pholidotans, and palaeanodonts. This new analysis provides compelling evidence that Eurotamandua is related to Palaeanodonta (Laurasiatheria: Pholidotamorpha) rather than to Xenarthra, thus separating it from xenarthrans at the superordinal level. Consequently, there is no evidence that Xenarthra ever reached the Old World.