The uniquely diverse taphonomy of the marine reptile skeletons (Sauropterygia) from the Lower Muschelkalk (Anisian) of Winterswijk, The Netherlands

Abstract

Having provided dozens of articulated, and even more disarticulated skeletons of marine reptiles with varying degrees of completeness, the Middle Triassic fossil deposit of Winterswijk, The Netherlands, might be considered the richest within the entire Germanic Basin concerning associated and partially articulated remains. Aside from these remains, a high number of isolated bones are also found. Among the various marine reptile taxa, the pachypleurosaur Anarosaurus and the nothosaur Nothosaurus are the most common. The skeletons and remains show diverse disarticulation patterns. These patterns range from mostly complete articulated skeletons to clustered and isolated bones. Interestingly, a large number of isolated articulated limbs is found, a pattern which is not known from other marine localities. Although numerous reports have been made on the taxa from Winterswijk, the taphonomy of the locality still remains poorly understood. Here, a series of methods are used to describe the taphonomy of 327 marine reptile specimens from the locality of Winterswijk in a qualitative manner. Furthermore, it is tested whether biofilms such as microbial mats could have had an influence on the preferential preservation of several body regions. Upon investigation, it is concluded that the taphonomy of Winterswijk is very complex and indeed depends on various factors such as: current activity, microbial activity, and anatomical differences between taxa. Finally, a total of 12 recurring patterns were identified within the dataset, which could largely be explained by the aforementioned factors.