Warm-blooded ichthyosaurs

December 2018

Yesterday the most important study I ever took part of was published in Nature.

Our paper, entitled "Soft-tissue evidence for homeothermy and crypsis in a Jurassic ichthyosaur" describes an exceedingly well-preserved ichthyosaur from the Lower Jurassic Posidonia Shale of Holzmaden in southern Germany. The specimen (MH 432), housed in the collections at Urweltmuseum Hauff, was first surveyed by Johan Lindgren and myself during a visit to Holzmaden in September 2015.

At that time, it was far from clear to us how spectacular the results of our study would be. From numerous analyses, we were able to demonstrate that the still flexible skin contains pigments and pigment cells, which indicate countershading; that is, the back side of the animal was dark while the belly was bright, similar to what is seen in modern whales such as orcas.

The skin itself was smooth and did not bear any scales or scutes. Another analogue to modern whales is that the specimen preserved blubber. Until now, blubber has only been found in marine mammals, not reptiles (save perhaps for the leatherback sea turtle). Its presence demonstrates that ichthyosaurs were warm-blooded. Additionally, we also identified remnants of the liver and other tissues.

Many thanks to Johan Lindgren for being such a great lead authors and to all fellow co-authors. It was pleasure to work with you all on that fantastic specimen. Photo courtesy (if not stated otherwise) Johan Lindgren.