Remarkably preserved fossil sea reptile reveals skin that is still soft

December 06, 2018

The remains of an 180 million-year-old ichthyosaur (literally 'fish-lizard') have been analysed, and the fossil is so well-preserved that its soft-tissues retain some of their original pliability. The study, published in Nature, contributes to our understanding on how convergent evolution works, and shows that ichthyosaurs adapted to marine conditions in a way that is remarkably similar to that of modern whales.

The ichthyosaur lived in what is today southern Germany during the Jurassic Period some 180 million years ago. At that time, the approximately two-metre long reptile swam in a vast ocean that was then covering large parts of present-day Europe.

Johan Lindgren of Lund University, Sweden, led the international collaboration that resulted in the most comprehensive and in-depth examination of a soft-tissue fossil ever undertaken. Among other things, the study reveals that the soft parts have fossilised so quickly that both the original cells and their internal contents are preserved.

"You can clearly see both the body outline and remains of internal organs. We can even distinguish the different cellular layers within the skin", explains Johan Lindgren.

The researchers identified blubber underneath the skin. To date, such specialized fat-laden tissue has only been found in modern marine mammals and adult individuals of the leatherback sea turtle. The presence of blubber indicates that ichthyosaurs had metabolic rates that were higher than are those of typical reptiles living today. These data could help explain why ichthyosaurs had an almost global distribution, even in cold waters, and how they could dive to considerable depths, as well as grow as fast as they did.

The team also examined remains of the animal's liver, which included part of the original biochemistry (e.g., eumelanin pigment and haemoglobin residues). The molecular and imaging analyses were performed in laboratories in Sweden, Germany, Japan and the USA.

"It's truly remarkable that the biomolecules we discovered so closely match the tissues that we could identify", says Johan Lindgren.

In the study, the researchers also succeeded in showing that the fossil contains tissues that still retain some of their original pliability, even though 180 million years have passed since the material was fresh. The team used chemicals to remove the mineral phase of the specimen, i.e. the inorganics that once turned the animal carcass into a petrified fossil.

"We then discovered that the soft parts retain a certain degree of elasticity", says Johan Lindgren.

The results also reveal the colouring of adult ichthyosaurs: the upper part of the body was dark, whereas the belly was light. This colouration acted either as camouflage or UV protection, or both. It may also have helped the animal to warm up faster in cold climates and/or after long and deep dives.

Not only do the results provide insights into the biology, physiology and ecology of derived ichthyosaurs, they also show how little we know about the fossilisation process and what can actually be preserved in the fossil record. Moreover, they could add to our knowledge on convergent evolution, as ichthyosaurs display an interesting mix of characteristics otherwise found in toothed whales (such as dolphins and porpoises) and the leatherback sea turtle.
-end-


Lund University

Related Fossil Articles from Brightsurf:

Fossil shark turns in to mystery pterosaur
Lead author of the project, University of Portsmouth PhD student Roy Smith, discovered the mystery creature amongst fossil collections housed in the Sedgwick Museum of Cambridge and the Booth Museum at Brighton that were assembled when phosphate mining was at its peak in the English Fens between 1851 and 1900.

New fossil seal species rewrites history
An international team of biologists, led by Monash University, has discovered a new species of extinct monk seal from the Southern Hemisphere -- describing it as the biggest breakthrough in seal evolution in 70 years.

How to fix the movement for fossil fuel divestment
Bankers and environmentalists alike are increasingly calling for capital markets to play a bigger role in the war on carbon.

New fossil ape is discovered in India
A 13-million-year-old fossil unearthed in northern India comes from a newly discovered ape, the earliest known ancestor of the modern-day gibbon.

Fossil growth reveals insights into the climate
Panthasaurus maleriensis is an ancestor of today's amphibians and has been considered the most puzzling representative of the Metoposauridae.

Australian fossil reveals new plant species
Fresh examination of an Australian fossil -- believed to be among the earliest plants on Earth -- has revealed evidence of a new plant species that existed in Australia more than 359 Million years ago.

Tracking fossil fuel emissions with carbon-14
Researchers from NOAA and the University of Colorado have devised a breakthrough method for estimating national emissions of carbon dioxide from fossil fuels using ambient air samples and a well-known isotope of carbon that scientists have relied on for decades to date archaeological sites.

Rare lizard fossil preserved in amber
The tiny forefoot of a lizard of the genus Anolis was trapped in amber about 15 to 20 million years ago.

Reconstructing the diet of fossil vertebrates
Paleodietary studies of the fossil record are impeded by a lack of reliable and unequivocal tracers.

Fossil is the oldest-known scorpion
Scientists studying fossils collected 35 years ago have identified them as the oldest-known scorpion species, a prehistoric animal from about 437 million years ago.

Read More: Fossil News and Fossil Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.