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Metatetrapous valdensis Nopcsa, 1923 and the Presence of Ankylosaur Tracks (Dinosauria: Thyreophora) in the Berriasian (Early Cretaceous) of Northwestern Germany

Metatetrapous valdensis Nopcsa, 1923 from the late Berriasian of northwestern Germany was the first dinosaur ichnotaxon ever attributed to a thyreophoran trackmaker. However, the subsequent lost of the original material made this identification and the status of the ichnotaxon questionable for many subsequent authors. This situation was aggravated by the fact that there are only very brief original descriptions accompanied by a single drawing. A reconsideration of the original description recognizes M. valdensis as a valid ichnotaxon, which, albeit showing great resemblance in pes morphology to similar ichnotaxa, stands out from them by a tetradactyl manus. It not only holds its original systematic attribution, but also has sparked early hypotheses on the phylogeny of dinosaurs already in 1922, possibly for the first time based upon tracks. Two surviving natural hypichnial casts of ankylosaurian pes imprints from the same stratum cannot be straightforwardly identified with the type material due to a lack of documentation. However, comprehensive circumstantial evidence, including complete accordance in size and morphology among others, strongly supports such an association. The tracks confirm the presence of ankylosaurs in this lacustrine-deltaic setting as a very rare element of the local dinosaur fauna.