Plesiosaurs are an extinct group of Mesozoic marine reptiles. Their fossil record ranges from the latest Triassic (approx. 200 million years ago) to the latest Cretaceous (approx. 65 million years ago), and they have a short body with four flippers, a long neck, and a head full of sharp teeth. They are unlike any modern day animal and were once described as looking like a snake threaded through the body of a turtle.
The five metre-long holotype specimen of ‘Plesiosaurus’ megacephalus, from the Jurassic of Street-on-the-Fosse, Somerset, was one of several plesiosaur specimens once displayed in the Bristol City Museum and Art Gallery during the first half of the 20th Century. As one of the earliest plesiosaurs to evolve it is an important species for understanding the early history of the group. Sadly, the fossil skeleton was destroyed along with many other specimens, when the museum was struck by a bomb during the Second World War. This destroyed fossil material is sometimes referred to as the ‘ghost collection’.
All was not lost, however. Moulds of some of the fossils had been taken before the war. In the case of ‘Plesiosaurus’ megacephalus, multiple casts of its skull and forelimb were produced prior to its destruction, and these had been deposited in the collections of several other museums (British Geological Survey, Keyworth; Natural History Museum, London; Trinity College, Dublin).
These casts recently provided a valuable resource for Dr Adam Smith, Curator of Natural Sciences and a palaeontologist at the Nottingham Natural History Museum, Wollaton Hall. Smith used the casts to conduct a research project on the ‘Plesiosaurus’ megacephalus, published this April in the open access journal Palaeontologia Electronica (18.1.20A p.1-19). The study was facilitated by The Bristol Museum and Art Gallery, who provided historical photographs of the ‘ghost collection’ from their archives. These show how the fossil skeletons appeared before they were destroyed (Figure 1). To assist with the project, the British Geological Survey produced three-dimensional digital laser scans of the casts as part of their JISC-funded ‘GB3D fossil types online’ project. The resulting virtual models can be rotated and studied on a computer screen, and even printed with a 3D printer (Figure 2, 3).
FIGURE 2. Plaster cast (BGS GSM 118410) of the holotype (BRSMG Cb 2335) skull of Atychodracon megacephalus (Stutchbury, 1846) in ventral (palatal) view. Three dimensional scan with texture (colour) removed. Scale bar = 100 mm.
The scientific study shows that ‘Plesiosaurus’ megacephalus is distinct from all other plesiosaurs, including Plesiosaurus, and so it is given a new name, Atychodracon, meaning ’Unfortunate Dragon’. This is in recognition of the unfortunate destruction of the original fossil, as well as the colloquial name ‘Sea Dragon’, sometimes applied to extinct swimming reptiles. The project also shows that fossil casts, and 3D laser scans, provide valuable data for palaeontologists - they can be described, measured, and coded into analyses. When the original fossil material has been lost, damaged or destroyed, the scientific value of casts increases even further. This study is the first publication to make use of the publicly available repository of 3D laser scans provided by the BGS. The Bristol Museum and Art Gallery is now investigating the possibility of using physical representations of their ‘ghost collection’ in future exhibitions, to bring long lost fossils such as Atychodracon ‘back to life’.
FIGURE 3. Plaster cast (BGS GSM 118410) of the ventral surface of the right forelimb of Atychodracon megacephalus (Stutchbury, 1846) (BRSMG Cb 2335).
Guest blog written by Adam Smith