Thursday, July 21, 2016

The Different Paleoenvironments of the Vellberg's Middle Triassic Lagerstätten


Schoch et al


The lacustrine deposits of Vellberg, southern Germany, rank among the richest vertebrate fossil-lagerstätten of the Triassic worldwide. Continued excavation over one decade produced two chondrichthyans, 14 taxa of bony fishes, seven temnospondyls, one chroniosuchian, the stem-turtle Pappochelys, two procolophonians, four lepidosauromorphs, a choristodere, four archosauriforms, three pseudosuchian archosaurs, and around ten further reptile taxa only known by teeth. Sedimentary facies, fossil assemblage composition, and taphonomy suggest this deposit comprises a succession of rather different water bodies, situated on a floodplain dominated by dolomitic muds: (1) a coal swamp with occasional reptiles and temnospondyls, (2) a large but shallow, brackish lagoon inhabited by Bakevellia, Acrodus, Nothosaurus, and the temnospondyl Plagiosternum, (3) a small and shallow, well-protected, oligohaline freshwater lake dominated by various temnospondyls, and (4) a larger (6 km) and deeper freshwater lake, again with a rich fauna of fishes, temnospondyls, and small aquatic reptiles that was eventually filled by dolomitic coastal muds. Reworking and desiccation cracks indicate repeated phases of regression and drought, during which bonebeds formed and skeletons of terrestrial tetrapods were deposited.

No comments: