The Muddy Water Surrounding Protoichthyosaurus and Ichthyosaurus Just Got a Little Clearer
A type of British Ichthyosaur, first identified nearly forty years ago, but then dismissed as a distinct genus, has been re-examined and found to be a new type of marine reptile after all. British palaeontologist Dr Robert Appleby, in 1979, conducted a review of Ichthyosaur fossil material found around the UK and announced a news species which he named Protoichthyosaurus. Two separate species were assigned to this genus P. prostaxalis and P. prosostealis. Erecting this genus with its two component species proved controversial and a number of other scientists have dismissed this assessment, reassigning the fossil material to the Ichthyosaurus genus.
One of the Fossil Specimens from the 1979 Marine Reptile Study
Picture Credit: National Museum of Wales/Dean Lomax
A detailed study which involved making comparisons between Protoichthyosaurus and Ichthyosaurus by Dean Lomax, (Manchester University), Rashmi Mistry (University of Reading) and Professor Judy Massare (State University of New York), published in the “Journal of Vertebrate Paleontology” has established Protoichthyosaurus as a separate genus once again.
The researchers found major differences in the number of bones in the front fin, or forefin, of both species. The team posit that this fundamental difference in anatomy probably reflects the way both species used their forefins to manoeuvre whilst swimming. Differences were also found in the skulls.
Scientists Studying the Fossil Material
Picture Credit: University of Nottingham
Fin Grabs Attention
During this research, another discovery about the fins was made, palaeontologist Dean Lomax explained:
“This unusual forefin structure was originally identified by Robert Appleby in 1979, but some of the historic specimens he examined had been ‘faked’, and this fakery had been missed until now. In some instances, an isolated fin of an Ichthyosaurus had been added to a Protoichthyosaurus skeleton to make it appear more complete, which led to the genuine differences being missed. This has been a major problem because it stopped science from progressing. We also found some pathological fins, including Ichthyosaurus fins with pathologies that mimic the Protoichthyosaurus forefin structure”.
Dean and Judy teamed up with former undergraduate student Rashmi Mistry, who had been studying an unusual Ichthyosaur in the collections of the Cole Museum of Zoology, (University of Reading), as she prepared her undergraduate dissertation.
“Whilst doing my dissertation in 2016, I studied several Ichthyosaurs in the collections, including a very small skeleton. It had an unusual forefin that matched Protoichthyosaurus, which I understood to be a widely unrecognised genus. However, when I contacted Dean, he was very excited. He told me that this little skeleton is the only known small juvenile Protoichthyosaurus.”
The Juvenile Protoichthyosaurus Specimen
Picture Credit: University of Reading
More Than Twenty Specimens of Protoichthyosaurus Identified
As a result of this extensive study, more than twenty specimens of Protoichthyosaurus have been identified. This is highly significant as each specimen (with a forefin) has the same structure. The specimens all date from the early Jurassic geological period (200-190 million years ago) and they are geographically dispersed with specimens reported from Dorset, Somerset, Leicestershire, Nottinghamshire, Warwickshire and Glamorgan (Wales)
Links with the Dinosaurs of China Exhibition
As part of his research, Dean examined a nearly complete skeleton which is part of the vertebrate collection at the museum of Nottingham. This specimen turned out to be different from all the other known examples of Protoichthyosaurus (autapomorphies concerning the cranium and the shape of the humeri). A new species of Protoichthyosaurus has been erected, it has been named Protoichthyosaurus applebyi, in honour of Dr Appleby and in recognition of his work some forty years ago that established the Protoichthyosaurus genus in the first place.
The Protoichthyosaurus applebyi Specimen
The fossil specimen is currently on display at the Nottingham Lakeside Arts centre, as part of the “Dinosaurs of China” exhibition. If you want to catch this marine reptile and take in all the beautiful feathered dinosaurs in this exhibition, you had better hurry, “Dinosaurs of China” closes at the end of the month.
Everything Dinosaur Team Members Viewed the Specimen at the “Dinosaurs of China” Exhibition
Picture Credit: Everything Dinosaur
The scientific paper: “The Taxonomic Utility of Forefin Morphology in Lower Jurassic Ichthyosaurs: Protoichthyosaurus and Ichthyosaurus” by Lomax, D. R., Massare, J. A. and Mistry, R. Published in the Journal of Vertebrate Paleontology.