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Thaumatodracon – the Wonder Dragon

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In 2012 I co-presented a poster at the SVP annual meeting on a new plesiosaur from Lyme Regis, UK (see my article about it here). The long awaited follow up paper was finally published this summer in the latest volume of Palaeontographica A (Smith and Araújo, 2017) and the beast now has a name, Thaumatodracon wiedenrothi, meaning ‘Wiedenroth’s Wonder Dragon’.

The Lower Saxony State Museum commissioned artist Luzia Soares to create a stylistic impression of Thaumatodracon. Copyright L. Soares 2017

Thaumatodracon was a top-predator that cruised around the shallow Tethys Ocean that covered Europe about 195 million years ago. It had a 60 cm long skull with dozens of sharp teeth, an estimated total body length of 6.5 m, and may have weighed around 2 tonnes. The specimen was collected from Lyme Regis in 1969 by Kurt Wiedenroth, an amateur German palaeontologist to whom we dedicated the new species name. The Niedersächsisches Landesmuseum Hannover (Lower Saxony State Museum) acquired the specimen later that year where it was subsequently prepared by Elijah Widmann during the 1990s.

Kurt Wiedenroth hunting for ammonites in Lower Cretaceous deposits near Hanover, Germany. Kurt discovered Thaumatodracon wiedenrothi in Lyme Regis in 1969. Photo courtesy of Sönke Simonsen.

The nearly complete skull and neck of this plesiosaur are exquisitely preserved, and Ricardo Araújo and I visited the Lower Saxony State Museum in Hanover in 2011, where we identified it as a new species that fills a gap in the fossil record of rhomaleosaurids. Diagnostic ones, anyway. The holotype of ‘Plesiosaurus’ macrocephalus, also from Lyme Regis, could well be a rhomaleosaurid, but since it is a juvenile it is difficult to diagnose. Our findings in Hanover were too late to include in my PhD thesis dedicated to rhomaleosaurids, but better late than never.

The preserved parts of the skeleton – the head and neck – are highlighted in dark grey

The holotype specimen, laid out in dorsal view.

Details and interpretation of the skull

In addition to a thorough comparative description, we conducted morphometric analyses to compare Thaumatodracon to all other rhomaleosaurid plesiosaurs. We found that the new taxon possesses transitional characteristics that are consistent with its intermediate position in the plesiosaur family tree. This is also more or less what we would predict to find because it is from the Sinemurian, which makes it stratigraphically intermediate between the older Hettangian rhomaleosaurid fauna (Atychodracon) and younger Toarcian rhomaleosaurid fauna (Rhomaleosaurus, Meyerasaurus).

The new genus is a nod to ‘Thaumatosaurus’, a powerful name that was once used interchangeably with Rhomaleosaurus. It was also widely applied to the holotype specimen of Meyerasaurus victor before I came along and made ‘Thaumatosaurus’ a nomen dubium (see my article about that here). So, I chose the name Thaumatodracon as atonement, but also because plesiosaurs were true wonders of the prehistoric world and Ricardo and I wanted to give this new species a name to reflects that.

Rhomaleosaurids have traditionally been regarded as pliosaurs. Although we called Thaumatodracon a pliosaur in our original poster presentation, the position of Rhomaleosauridae within Plesiosauria has since become disputed. Several studies now suggest that the rhomaleosaurid family diverged from other plesiosaurs before the pliosaur/plesiosauroid dichotomy, which is why we avoid calling Thaumatodracon a pliosaur in our paper.

The journal has requested that I do not share the PDF publicly, but I’m free to email it, so drop me an email if you’re interested: [email protected]

Reference
Smith, A.S. and Araújo, R. 2017. Thaumatodracon wiedenrothi, a morphometrically and stratigraphically intermediate new rhomaleosaurid plesiosaurian from the Lower Jurassic (Sinemurian) of Lyme Regis. Palaeontographica Abteilung A, 308 (4-6), 89-125. doi:10.1127/pala/308/2017/89

Written by Adam S. Smith

August 29th, 2017 at 5:28 pm

Resurrecting the Unfortunate Dragon

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The five metre-long holotype specimen of ‘Plesiosaurus’ megacephalus, from the Jurassic of Street-on-the-Fosse, Somerset, was one of several plesiosaurs once displayed in the Bristol Museum and Art Gallery. 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 important specimens when the museum was struck by a bomb during the Second World War. This destroyed fossil material is sometimes referred to today as the ‘ghost collection’.

Atychodracon skeleton

Historical photograph of the holotype skeleton (BRSMG Cb 2335) of Atychodracon megacephalus (Stutchbury, 1846). Bristol City Museum & Art Gallery. Length of skeleton equals 4960 mm.

Thankfully, all was not lost. Moulds had been taken from some of the fossils before the war, and in the case of ‘Plesiosaurus’ megacephalus, multiple casts of its skull and forelimb were produced prior to its destruction. These were deposited in the collections of several museums, including the British Geological Survey (BGS), Keyworth; Natural History Museum, London; and Trinity College, Dublin.

The casts provide a valuable resource that I was able to use to describe ‘Plesiosaurus’ megacephalus in an article published this year in the open access journal Palaeontologia Electronica (18.1.20A p.1-19). The study focused on the casts held in the BGS, but was also facilitated by The Bristol Museum and Art Gallery who provided historical photographs of the ‘ghost collection’ from their archives. The photo (above) shows how the entire fossil skeleton appeared before it was destroyed. The BGS also produced three-dimensional digital laser scans of the casts as part of their JISC-funded ‘GB3D fossil types online’ project. The resulting virtual models are free to view or download (here) and can be rotated on screen or 3D-printed.

Atychodracon skeleton

Three dimensional scan with texture (colour) removed of plaster cast (BGS GSM 118410) of the holotype (BRSMG Cb 2335) skull of Atychodracon megacephalus (Stutchbury, 1846) in ventral (palatal) view. Scale bar equals 100 mm.

The skeleton of ‘Plesiosaurus’ megacephalus is distinct enough from all other plesiosaurs, including Rhomaleosaurus and Eurycleidus, to warrant a new genus name. I called it Atychodracon, meaning ’Unfortunate Dragon’, in reference to the unfortunate destruction of the original fossil material. This project also demonstrates that casts of fossils, and 3D laser scans, can provide valuable data for palaeontologists – they can be described, measured, and coded into analyses. When 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’.

Find out more by checking out the article at Palaeontologia Electronica.

Atychodracon skeleton

Plaster cast (BGS GSM 118410) of the ventral surface of the right forelimb of the holotype of Atychodracon megacephalus (Stutchbury, 1846) (BRSMG Cb 2335). 1, three dimensional scan with texture (colour) removed, 2, photograph, 3, interpretation.

Written by Adam S. Smith

October 18th, 2015 at 12:01 am

Pliosaurus kevani – the Weymouth Bay Pliosaur

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I’ve been rather quiet again recently, however, as coauthor of an article just published in PLOS ONE, I’ve good reason to come out of my shell today. The new paper describes and names the Weymouth Bay Pliosaur, a spectacular almost complete skull over 2m long. As discussed in the open access paper (take a look), the specimen is sufficiently different from all other pliosaurs to warrant a scientific name of its own, Pliosaurus kevani.

Weymouth Bay Pliosaur

Pliosaurus kevani was named to honour Kevan Sheehan, the Osmington Mills café owner who collected most of the skull, piece by piece, over a period of eight years. Kevan collected chunks up to 60 kg each as they weathered out from the Jurassic aged Kimmeridge Clay Formation sea-cliff. The specimen was purchased with funding secured by Dorset County Council’s museum service from the Heritage Lottery Fund Collecting Cultures programme, and Dorset and Devon county councils. It was prepared between 2010 and 2011 by Scott Moore-Fay and went on public display in Dorchester County Museum in July 2011.

Richard Forrest, who was involved with the project from the beginning, first had the idea of putting together a ‘dream team’ of British plesiosaur specialists to study and describe the skull. This is the first collaboration of its kind among plesiosaur researchers (as far as I know), and I feel lucky to have had the opportunity to contribute to it under the driving force of our lead author, Roger Benson.

Weymouth Bay Pliosaur

Roger Benson (left) and Richard Forrest (right) collecting data from the Weymouth Bay Pliosaur – Pliosaurus kevani

The massive skull has a long snout, circular orbits, huge temporal openings for the jaw musculature, and a deep mandible. Large portions of the skull have been crushed flat during fossilisation, so one of my tasks was to reconstruct the skull to show how it might have appeared before it was flattened. After several versions and much input from Mark Evans, I’m pleased with how it turned out, and I think we’ve produced a pretty accurate reconstruction of Pliosaurus. On the basis of this reconstruction I’ve also had a go at restoring the life appearance of P. kevani in profile. Despite its large size and massive teeth, the head is rather gracile.

Weymouth Bay Pliosaur
Weymouth Bay Pliosaur

Pliosaurus belongs to a group of plesiosaurians known as thalassophonean pliosaurs. If you haven’t heard of them before, that’s because the name Thalassophonea, or “sea slayers”, was proposed just this year (Benson & Druckenmiller, 2013) for a natural group of derived giant pliosaurids including Pliosaurus, Liopleurodon, and Kronosaurus. Thalassophoneans were macropredators, that is, giant predators doing the sort of dirty work in the Middle-Late Jurassic and Cretaceous that rhomaleosaurids did in the Early Jurassic. The paper also discusses the evolution of pliosaurids. The earliest thalassophoneans have a long mandibular symphysis, but in later members the symphysis becomes shorter. This trend is related to a shift in the dietary habits of pliosaurs from primarily fish-eaters to macropredators. In conjunction with this trend, we demonstrate that pliosaurids tend to follow Cope’s Rule – they get larger throughout their evolutionary history.

Weymouth Bay Pliosaur

We also name two other new species of Pliosaurus in the paper, P. westburyensis and P. carpenteri, based on material in the Bristol Museum & Art Gallery from Westbury, Wiltshire. Again, there are morphological aspects of these specimens that distinguish them from one another, but don’t justify new genus names. So, add these new species to the existing list of valid Pliosaurus species and we find ourselves with a rather large number of species within a single genus. The others being: P. funkei, also known as Predator X, P. brachydeirus, P. rossicus, and there might be one or two more pending thorough description of the material. Some invalid species of Pliosaurus have recently been sunk too. Future research might show greater generic diversity among these species, but that’s really dependent on the discovery of more satisfactory fossil material.

Written by Adam S. Smith

May 31st, 2013 at 9:21 pm

A new Lyme Regis pliosaur

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Earlier this month I co-authored a poster at SVP 2012 describing a new pliosaur from the Sinemurian of Lyme Regis (Smith and Araújo, 2012). I was unable to attend the conference in person so my collaborator and friend Ricardo Araujo was on hand to present our preliminary findings.

Ricardo Araújo stands proudly next to our poster at SVP 2012. Ricardo is conducting a PhD on plesiosaurs at the Southern Methodist University, Texas.

The spectacular specimen was discovered at Black Ven, Lyme Regis, and was acquired by the Niedersächsisches Landesmuseum, Hanover, where it was expertly prepared in the 1990s by their preparator, Elija Widman. The fossil consists of an almost complete skull and vertebral column.

The Lyme Regis pliosaur as articulated

As explained in our poster, the fossil represents a new taxon that is both stratigraphically and morphologically intermediate between known Hettangian and Toarcian rhomaleosaurid pliosaurs. Which makes perfect sense. A legible (just about) jpg version of the poster is available here or by clicking the small version below, and a PDF of the abstract is available here. This is very much a work in progress though and more of a sneak preview than a final word. We have a paper in prep which will provide a more detailed description of the specimen.

Poster for SVP 2012

References
Smith, A.S. and Araújo, R. 2012. A new rhomaleosaurid pliosaur from the Sinemurian (Lower Jurassic) of Lyme Regis, UK. Program and abstracts, 72nd Annual Meeting of the Society of Vertebrate Paleontology, Supplement to the online Journal of Vertebrate Paleontology, 74. [PDF here]

[Incidentally, how does one cite an SVP abstract correctly these days?]