Evidence of a preservational gradient in the skeletal taphonomy of Ichthyopterygia (Reptilia) from Europe

- Ichthyopterygians underwent short transport and floating phases, reaching the sediment surface soon after death.
- Reduction of carcass condition progressed generally from peripheral (gastral rib, limb) to medial (vertebral) units.
- Variation in preservation highlights a taphonomic gradient across European localities related to proximity to land.
- Water circulation and current activity were relatively more intense closer to major landmasses.
- The study demonstrates the importance of contextual information over number of specimens.

Studies of preservation have allowed environmental conditions at numerous localities in space and time to be inferred. However, in the search for sufficient vertebrate specimens to provide a large dataset, details of specimen taxonomy, geographic origin and stratigraphic level are often ignored or not collected. Any preservational variation identified as a result is therefore from a broad range rather than a specific group, locality or time. The effect of this limitation, mainly regarding the loss of crucial information on environmental processes in ancient settings and the biology of long extinct organisms, is demonstrated using specimens of Ichthyopterygia (Reptilia). Taphonomic analysis of a dataset of 173 specimens infers a consistent reduction of skeletal condition from peripheral to medial within a carcass and a taphonomic pathway involving minimal floating and prolonged residence on the sediment surface. The same dataset divided into three sub-datasets, from the Middle Triassic Besano Formation, Lower Jurassic Blue Lias Formation and Lower Jurassic Posidonia Shale Formation, highlight preservational variation, in the extent of loss of articulation and completeness that follows an environmental gradient related to proximity to major landmasses.