Unexpected temnospondyl diversity in the early Carnian Grabfeld Formation (Germany) and the palaeogeography of metoposaurids

The Middle–Late Triassic Grabfeld Formation formed in a generally arid, hostile setting with frequent evaporation under alternating sabkha and playa conditions. Here we report evidence of four temnospondyl taxa from the upper part of the sequence (‘Bunte Estherienschichten’), including (1) Metoposaurus sp., (2) a capitosaur, (3) Gerrothorax sp. and (4) Plagiosternum sp. This early Carnian assemblage provides the stratigraphically oldest evidence of metoposaurids and the last report of plagiosternines in the Central European Basin. The stratigraphic age of these strata and the occurrence of Metoposauridae therein sheds new light on the palaeogeographic distribution of the group and their occurrence before the Carnian Pluvial Event.