The skull of a 200-million-year-old marine reptile has been scanned in 3D for the first time, revealing the presence of branching canals that were once blood vessels and nerves.
The discovery of such a well-preserved, Early Jurassic ichthyosaur – literally “fish lizard” – is unique in that most fossils from this age are “pancaked”, squished and distorted from millenniums of sediment and time.
"The three-dimensional nature of this ichthyosaur, along with its preserved braincase, is incredibly rare for an Early Jurassic ichthyosaur, especially considering that some of the braincase bones even show impressions of the actual brain," said palaeontologist Dean Lomax from The University of Manchester to IFLScience.
This fossil was found in a hard, blue-grey clay around 1.2 meters (4 feet) below ground in Warwickshire, England, directly on top of a brown grit layer containing extinct oysters called devil's toenails (Gryphaea bivalves). A plesiosaur vertebra and an isolated shark tooth were also collected with the specimen.
Using computerized tomography (CT) scanning technology, the team were able to digitally reconstruct the 0.8-meter (2.6-foot) skull. Although museum records identify the creature as a Ichthyosaurus communis, the team believes it belongs to a rarer species called Protoichthyosaurus prostaxalis. At up to 4 meters (13 feet) in length and a skull almost twice as long as any other specimen of this species, it’s the largest of its kind found so far.
"The two species are distinguished on the basis of various features. However, the key features lie in the size, shape and contact of individual bones in the skull, and with the number and position of fingers in the forefin," said Lomax.
The scans also revealed material that wasn’t exactly bone: wood, clay, and plaster. These were used by the curators decades before to hold the skull fragments together.
“There were several areas reconstructed in plaster and clay, and one bone was so expertly modeled that only the scans revealed part of it was a fake,” said University College London researcher Dr Laura Porro, co-author of the study published in PeerJ.
While ichthyosaurs were no towering T. rex or bony-plated stegosaurus, they were impressive in their own right. They were highly specialized marine creatures with large eyes and nostrils positioned far back on the top of their skull, suggesting they were air-breathers similar to modern whales and dolphins. Be this as it may, they're not related. Instead, they’re an example of convergent evolution – two lineages independently evolving similar features to cope with similar environmental demands.
“It’s taken more than half a century for this ichthyosaur to be studied and described, but it has been worth the wait,” added Lomax. “Not only has our study revealed exciting information about the internal anatomy of the skull of this animal, but our findings will aid other palaeontologists in exploring its evolutionary relationship with other ichthyosaurs.”