A review of ichthyosaur (Reptilia, Ichthyopterygia) soft tissues with implications for life reconstructions

The dolphin-like ichthyosaurs – also known as ‘fish lizards’ – are extinct marine reptiles that roamed the Mesozoic oceans for some 160 million years. As for most ancient vertebrates, our knowledge of these iconic animals largely derives from biomineralized hard parts (teeth and bones). However, soft tissues are also known from a number of Lagerstätte specimens, and have opened up new avenues for deciphering their biology and ecology. Herein, we present a review of ichthyosaur research and life style iconography with particular focus on soft-tissue structures and inferences made from these, including aspects of coloration and thermoregulation. We then distill novel insights on ichthyosaur anatomy and physiology gained from an exceptionally preserved, sub-adult specimen of the parvipelvian Stenopterygius from the Jurassic Posidonia Shale in Germany, and describe the process in which a detailed, three-dimensional reconstruction in scale 1:1 was produced. Our new sculpture is based on empirical evidence obtained directly from the fossil record, including uniquely preserved soft-tissue structures (e.g., original pigments and blubber), resulting in the scientifically most up-to-date reconstruction of an ichthyosaur currently available.