Dean R Lomax (UK)
Ichthyosaurs are extinct marine reptiles that superficially resemble dolphins and sharks, but are neither. They are most definitely not ‘swimming dinosaurs’. In fact, they were fully aquatic marine tetrapods that lived in the seas, while their more famous counterparts – the dinosaurs – roamed the land.
They achieved a worldwide distribution and remains have been discovered from the late Early Triassic to the early Late Cretaceous, and hundreds of species have been described (McGowan and Motani, 2003). The coastal town of Lyme Regis, situated on the Dorset coast, is often seen as the birthplace of ichthyosaurs. Many ichthyosaurs were collected from here during the early nineteenth century and were first brought to the attention of the scientific world by a fantastic young woman called Mary Anning (see below).
The focus of this article is based on the most famous ichthyosaur genus, Ichthyosaurus, which lends its name to the group. The first species, I. communis, was described in 1821; the second, I. breviceps, was described in 1881; and the third, I. conybeari, was described in 1888. Since then, lots of ‘Ichthyosaurus’ have been described and all have since been found to represent distinct ichthyosaur genera and species, until now.
In 2008, I began researching the collections of my hometown museum, Doncaster Museum & Art Gallery. One specimen, the key ichthyosaur of this study, was shown to me as “an exceptional cast” (this was as part of an exhibition I created at the museum; see my article in Issue 21 of Deposits: Fabulous Fossils’ exhibition at Doncaster Museum and Art Gallery). However, I immediately recognised that it was an original specimen and might be important. In addition to this, I went on to describe stomach contents preserved with the specimen, which formed my first ever peer reviewed publication (Lomax, 2010b).
Little information was recorded with the specimen and the location where it was found was unknown. However, I discovered a single belemnite preserved in the matrix, next to the skull. The belemnite was identified and noted to have come from only one specific horizon in the world, exposed around Charmouth. This rock layer dated to the Jurassic Period and to a time known as the Pliensbachian, specifically the Charmouth Mudstone Formation, Stone Barrow Marls (previously called the Belemnite Marls), Bed 110. Pliensbachian ichthyosaurs are rare and this specimen represents the world’s most complete example. I determined that the specimen belonged to the genus Ichthyosaurus, but was unable to identify the species and believed it to be something unusual.
In 2010, after a couple of years of independent research, I teamed up with Prof Judy Massare (Brockport College, NY, USA), a renowned ichthyosaur expert, and together we began a scientific adventure that would take up much of the next four years of my academic research.
Jurassic sushi – preserved stomach contents
A large, extensive dark mass lay between the ribs of the ichthyosaur. This mass is different to the surrounding matrix and the bones of the ichthyosaur. On closer inspection under magnification, I identified hundreds (perhaps thousands) of tiny hook-shaped fragments. These hooklets belonged to the tentacles of squid-like animals, called belemnoteuthids (Lomax, 2010b; Lomax and Massare, 2015). Additionally, a single fish scale was found, although this was positioned just outside of what is presumed to be the stomach contents. This demonstrates that the ichthyosaur was feeding on squid, and perhaps fish also, before it died.
Ichthyosaurs possess many features that are morphologically distinct from one another. One key feature is their humerus (plural: humeri) bone. Prof Massare and I determined that the humeri of our specimen had to be removed to distinguish the specimen as something new. This was skilfully undertaken by palaeontologist and preparator, Nigel Larkin; paid for by an externally funded project (CIRCA), as part of an award from the Esmée Fairbairn Foundation to Doncaster Museum Service.
The result was two removed ichthyosaur bones. These were moulded and copies were produced; and they were even CT-scanned at the Royal Veterinary College, London. The humeri further assisted with the identification of the ichthyosaur as Ichthyosaurus, but in other features were unusual and suggested something new. These include a short, robust humerus with prominent processes; a femur with proximal width almost as large as distal width; and a very small femur relative to the humerus. One of the most unusual features was a ‘depression’ in the humerus.
A new species defined (male or female?)
To test our hypothesis of the importance of these new features, over the course of four years, we undertook numerous research visits to lots of museums across the UK, Europe and the USA. This included the examination of, perhaps, over a thousand individual ichthyosaur specimens. The key focus was to examine features of the new species with those of other Ichthyosaurus species, to assist in determining the new species as something distinct entirely.
As part of the research, we identified four additional specimens, also from around the Charmouth/Lyme Regis area, which we were able to refer to the new species. Looking at ontogenetic features (mature/immature) in ichthyosaurs, we determined that the Doncaster specimen was probably an adult, and the others represented a subadult and three juveniles.
Yet, a problem occurred. Here, we had two groups of specimens, one showing all of the key features of the humerus and the other showing all of the features of the new species except those of the humerus. Few studies on sexual dimorphism in ichthyosaurs have been undertaken, so we examined the reptile record (extinct and extant) of sexual difference in limbs and found that several groups display distinct differences in limb shape between males and females. Therefore, for the first time, it may be possible to differentiate between male and female ichthyosaurs, at least in this species. It is hoped that similar studies will be applied to other ichthyosaur genera.
What’s in a name?
Before our study, three species of Ichthyosaurus were considered valid, all recorded almost exclusively from Dorset, with the last species described in 1888. Therefore, our new species is the first to be validly described in almost 130 years. As mentioned previously, many ichthyosaurs from Dorset were collected by Mary Anning. Mary lived at Lyme Regis in Dorset, and was the first person (ever) to bring the ichthyosaurs – along with many other kinds of fossils – to the attention of the scientific world. It was Mary and her brother, Joseph, who discovered the first ichthyosaur to be scientifically recognised, in about 1811.
However, remarkable, no ichthyosaur has ever before been named after Mary and we wanted to change that. In her honour, we named the new species Ichthyosaurus anningae. In fact, one of the additional specimens referred to our new species, held at the Natural History Museum in London, was even collected by Mary herself. A touch of serendipity. Personally, it is truly an honour to name a new species, but to name it after somebody who is intertwined with such an important role in helping to sculpt the science of palaeontology, especially in Britain, is something that I’m very proud of.
Our extensive, essentially seven year study, was brought together and our research was published this year in a leading vertebrate palaeontology journal, Journal of Vertebrate Paleontology. The specimen tells an exceptional story, from initially being mistaken for a copy to representing a holotype of a brand-new species named after the world-renowned, Mary Anning. Science is awesome.
And one final thought. A discovery of this magnitude demonstrates the further importance of examining small, local museum collections. Who knows what you might find?
About the author
Dean Lomax is a palaeontologist from Doncaster, England. Dean works on palaeontological projects across the world, but especially in the UK, across Europe and the USA. He researches fossils and writes books, articles and peer reviewed scientific papers. At the time this article was written, he was a Visiting Scientist at the University of Manchester, UK and an Honorary Research Associate at Doncaster Museum & Art Gallery.
Firstly, thanks go to my co-author, Prof Judy Massare, for her constant help and support. I would also like to thank Doncaster Museum for allowing our study of the specimen. The preparation was funded by the Esmée Fairbairn Foundation, as part of a grant awarded to Doncaster Museum.
References and further reading
Lomax, D. R. and Massare, J. A. (2015). A new species of Ichthyosaurus from the Lower Jurassic of West Dorset, England. Journal of Vertebrate Paleontology.
Lomax, D. R. and Tamura, N. (2014). Dinosaurs of the British Isles. Siri Scientific Press, Manchester. pp. 416.
Lomax, D. R. (2010b). An Ichthyosaurus (Reptilia, Ichthyosauria) with gastric contents from Charmouth, England: First report of the genus from the Pliensbachian. Paludicola, 8: 22–36.
Lomax, D. R. (2010a). Fabulous Fossils exhibition at Doncaster Museum and Art Gallery. Deposits, 21: 23–25.
McGowan, C. and Motani, R. (2003). Handbook of Paleoherpetology, Part 8 Ichthyopterygia. Verlag Dr. Friedrich Pfeil, Munich, pp. 175.
Torrens, H. S. (1995). Mary Anning (1799–1847) of Lyme; ‘the greatest fossilist the world ever knew’. British Journal for the History of Science 28: 257–84.
www.deanrlomax.co.uk – The personal website of the author.