The largest specimen of Protoichthyosaurus prostaxalis discovered so far recognized thanks to modern technologies

Protoichthyosaurus prostaxalis during a CT-scan (Photo courtesy University of Manchester. All rights reserved)
Protoichthyosaurus prostaxalis during a CT-scan (Photo courtesy University of Manchester. All rights reserved)

An article published in the journal “PeerJ” describes the examination of the specimen of a marine reptile that lived during the Jurassic period, about 200 million years ago. A team of researchers submitted it to an advanced CT-scan that allowed to examine it in depth and to conclude that it belongs to the species Protoichthyosaurus prostaxalis while originally it was identified as a specimen of Ichthyosaurus communis.

The species Protoichthyosaurus prostaxalis was described for the first time in 1979 and, together with the species Protoichthyosaurus applebyi, the other identified in the genus Protoichthyosaurus, has been for many years the subject of arguments about their correct classification. The problem was in the similarities with the genus Ichthyosaurus, described for the first time over a century before. An article published in October 2017 in the “Journal of Vertebrate Paleontology” presented evidence of the validity of the genus Protoichthyosaurus due to the differences with the species of the genus Ichthyosaurus.

Maybe the matter hasn’t been settled, but paleontologist Dean Lomax of the British University of Manchester, one of the world’s leading ichthyosaur experts, participated in that research. Lomax is also the lead author of this new research on another ichthyosaur fossil so it’s normal for him to use that taxonomy.

In 1955, fossils of almost 200 million years ago were discovered at Fell Mill Farm in Warwickshire, England. The specimen, an incomplete skeleton, was identified as belonging to an Ichthyosaurus communis but wasn’t formally studied. Only in 2014, as part of a project at the Thinktank Science Museum, Birmingham, Dean Lomax and his colleagues Nigel Larkin and Laura Porro started studying it.

This specimen is of a rare type because generally fossils are more or less crushed so their original structure is distorted while in this case there was an excellent preservation at 3D level. This enabled to obtain an accurate reconstruction of its appearance using an advanced CT-scan. Some missing parts of the skull were recreated mirroring the ones on the other side as a model.

Based on various characteristics of its skull, the researchers reclassified the specimen, assigning it to the species Protoichthyosaurus prostaxalis, unknown at the time of the first identification. The skull is almost twice the length of any other known Protoichthosaosaurus specimen.

By now the cases of use of modern technologies in the field of paleontology have become common, also because they show all the advantages that derive from it. The study of a fossil known for over 60 years offered a lot of new information to classify it correctly and to better understand its species’ relationship with other ichthyosaurs.

Protoichthyosaurus prostaxalis reconstruction (Image courtesy Bob Nicholls. All rights reserved)
Protoichthyosaurus prostaxalis reconstruction (Image courtesy Bob Nicholls. All rights reserved)

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