Redescription of Seymouria sanjuanensis (Seymouriamorpha) from the Lower Permian of Germany based on complete, mature specimens with a discussion of paleoecology of the Bromacker locality assemblage

ABSTRACT

Two nearly complete, articulated, mature specimens of the amphibian Seymouria are described from the Lower Permian Tambach Formation, lowermost unit of the Upper Rotliegend, of the Bromacker locality in the mid-region of the Thuringian Forest near Gotha, central Germany. They are assigned to S. sanjuanensis, known elsewhere only from the Lower Permian deposits of Wolfcampian age in the southwestern United States. This confirms an earlier referral of two immature specimens from the same locality to this species. The new specimens are unusual in being highly ossified and allow for the first time a complete description of the carpus and tarsus of Seymouria.

The Bromacker Seymouria specimens are part of an assemblage that is unique among Lower Permian localities in Europe in its taxonomic composition and its depositional environment. The Bromacker vertebrate assemblage includes many taxa found elsewhere only in the Lower Permian of the United States. All are adapted to a highly terrestrial existence, and the herbivore Diadectes and a closely related diadectid yet to be described are the most abundant forms, accounting for over half the articulated specimens encountered. Carnivorous, pelycosaurian-grade synapsid reptiles are exceedingly rare.

Fossils at the Bromacker quarry were preserved near the center of a small, internally drained, Early Permian basin, the Tambach Basin. The vertebrates of this extraordinarily rich quarry are commonly excellently preserved, often complete and articulated, and occur almost exclusively in sheet-flood deposits that were almost certainly responsible for their death and burial with little or no transport; only minor attritional processes are evident. Relationships of the paleoenvironments and the biology of the vertebrates of the Bromacker locality based on the stratigraphy, paleontology, sedimentology, and basinal context of the Tambach Formation indicate that the Bromacker assemblage may represent the earliest known and best documented Early Permian example of a truly terrestrial “uplands” ecosystem. It apparently evolved and maintained itself independent of contemporary, water-based food chains that included aquatic and semi-aquatic forms.