First well-established track-trackmaker association of Paleozoic tetrapods based on Ichniotherium trackways and diadectid skeletons from the Lower Permian of Germany

摘要

As a single stratigraphic Source and site of high-fidelity vertebrate trackways and superbly preserved skeletons, the Lower Permian Tambach Formation, lowermost unit of the Upper Rotliegend, of the Bromaker locality in the middle part of the Thuringian Forest near Gotha. central Germany, provides a unique opportunity of matching late Paleozoic trackways with their trackmakers. Here the track-trackmaker association is firmly established between two species of the ichnogenus Ichniotheriun, Ichniotherium cottae and Ichniotherium sphaerodactylum, and the skeletal fossils of the closely related diadectids Diadectes absitus and Orobates pabsti, respectively. These are the first well-documented species-level identifications of the trackmakers of Paleozoic trackways. The Ichniotherium ichnospecies are principally separated by the relative lengths of the digits of the pes imprint and the degree of overstepping of the pes and manus imprints. Both characters are shown to be clearly due to differences in the number and lengths of phalangeal elements and the number of presacral vertebrae of the diadectid species. The unique methods employed here in establishing the track-trackmaker associations provide not only an innovative data source for studying the evolutionary biology, paleo-biogeography. and locomotor behaviour of the trackmakers, but also a valuable methodology for evaluating taxonomic concepts in vertebrate ichnology.