A Rare Occurrence of Permian Tetrapod Footprints:Ichniotherium cottaeandIchniotherium sphaerodactylumon the Same Stratigraphic Surface

Ichniotherium Pohlig, 1892 is a principal morphotype of Carboniferous-Permian tetrapod footprints referred to diadectomorphs. Though these tracks are relatively abundant in paleoequatorial regions of Pangea, the Cisuralian Bromacker locality in central Germany, is the only known place with co-occurring Ichniotherium ichnospecies. Ichniotherium cottae Pohlig, 1885 and Ichniotherium sphaerodactylum Pabst, 1895 are well studied from the German fossil site but tracks of the two ichnospecies have reported to be almost exclusively preserved on separate specimens. Here, we describe two rare cases where I. cottae and I. sphaerodactylum tracks occur close each other on the same slab coming from the Bromacker quarry. In order to explain the exceptional occurrence of the two Ichniotherium ichnospecies and the higher relative abundance of I. sphaerodactylum at the Bromacker site, various reasons are discussed, from which the paleoecological ones linked to the time of impression (Hypothesis A) or to the trackmaker areal distribution (Hypothesis B) seem to be the most likely.