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Monograph on Rhomaleosaurus thorntoni

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Many readers will be familiar with the giant plesiosaur on display in the marine reptiles gallery of the Natural History Museum, London. This is a cast of the 7 metre long holotype of Rhomaleosaurus cramptoni, the original of which is housed in the National Museum of Ireland (Natural History) and formed the basis for my PhD thesis back in (time flies!) 2007. However, The Natural History Museum, London, also has its very own massive (also ~7 m long) and quite real Rhomaleosaurus type specimen to rival the ‘Dublin Pliosaur’ in size. NHMUK PV R4853, the mighty Rhomaleosaurus thorntoni, is from the Toarcian (Lower Jurassic) of Northamptonshire. It was donated to the museum prior to 1922 but has never been described and figured in its entirety before.

Rhomaleosaurus cramptoni

Rhomaleosaurus cramptoni cast on display in the NHM, London

 

My newest paper, co-authored with Roger Benson (Smith & Benson 2014), provides a detailed description and photographic atlas of the entire skeleton of Rhomaleosaurus thorntoni, and it was published by the Palaeontographical Society just in time for me to distribute copies to colleagues at the SVP annual meeting in Berlin last November (2014). Few monographs of this kind, i.e. a comprehensive treatments of a single taxon, exist for plesiosaurians, especially up-to-date ones, so the paper should prove useful. The monograph includes 35 photographic plates depicting, essentially, every bone in the skeleton from multiple angles. We describe the skeleton in detail and figure the more complicated elements as interpretive illustrations. It’s just a bigger than average descriptive paper, really, but one that has been many years in the making (even more than it usually takes!). I’ve been waiting for the published monograph to be listed on the Palaeontographical Society publications page prior to posting this article, but since it is not yet forthcoming I decided to post this anyway. I’ll update this blog entry with a link to the volume once it is listed. [Edit – here is the link]:

Rhomaleosaurus ilia

Rhomaleosaurus thorntoni ilia (Plate 33 from Smith & Benson [2014])

The entire manuscript, including the photographs and figures, is completely new: this is not a rehash of my PhD thesis on Rhomaleosaurus. The skeletal reconstruction is brand new as well and I hope that it comes to replace my previous reconstruction of Rhomaleosaurus in time, which I was never completely satisfied with (figured in Smith [2007], Smith & Dyke [2008], and Smith [2013]). It is important to highlight that the new reconstruction represents R. thorntoni specifically, which we demonstrate is a distinct species, whereas the previous reconstruction represented Rhomaleosaurus sp. using R. cramptoni where possible and R. thorntoni as a proxy where not. As such, the original reconstruction was a mishmash of two different species, with related scaling errors. Most of the differences apparent between the new and old reconstructions are, however, due to stylistic improvements and a greater attention to detail, rather than genuine anatomical differences between R. cramptoni and R. thorntoni. The lateral view, especially, had some perspective issues with the ribs and limbs, which are corrected in the new reconstruction. There is still some margin for error in the proportions of the tail and neck in the new reconstruction because these are incomplete in the holotype (and only known specimen) of R. thorntoni, but I’m much more satisfied with it.

Rhomaleosaurus thorntoni

Rhomaleosaurus thorntoni reconstruction. Scale bar = 1m.

There is some doubt over the systematic position of rhomaleosaurids. They are traditionally regarded as pliosaurs, but they might not really be included within that clade, so for this reason we refrained from referring Rhomaleosaurus to Pliosauroidea in the title. We don’t include a cladistic analysis in our monograph to investigate this question, but we do summarise all previous ones and identify areas of relationship consensus within the clade Rhomaleosauridae. More cladistic work is required to confirm whether rhomaleosaurids are an early plesiosaurian offshoot, or pliosaurs proper.

Rhomaleosaurid cladograms

Ingroup relationships of rhomaleosauridae according to different researchers (text-fig 11 from Smith & Benson [2014])

So, where’s the PDF? Sadly, there isn’t one, and this has been discussed and debated in some detail over at SV-POW (here). I say ‘there isn’t one’, but what I really mean is that distribution of the PDF is forbidden, since a beautiful PDF does exist (I was annotating it in the final proof stages). I was hopeful that permission would be granted for me to share the final PDF along with the hard copies provided for authors to distribute, but it was not to be. Of course, I’m disappointed about the barrier this puts between my research and potential readers, and I’m concerned about the impact this might have on it being cited. However, the hard copy is a quality publication, which can be thought of as more of a book than a paper. Those individuals that require it for research purposes can always request one from me directly – I can’t make promises but drop me an email if you have a serious interest ([email protected]).

The Palaeontographical Society funded some of my visits to the Natural History Museum to see the fossil material and this influenced my decision to select the Monograph of the Palaeontographical Society as a publication venue for this work. Plus, the format suits such an exhaustive treatment. I’d  like to thank the editor, Yves Candela, who made a significant contribution to the volume and coordinated the whole process.

Update: The monograph is now available for sale from the Pal Soc website here.

References:

Smith, A. S. 2007. Anatomy and systematics of the Rhomaleosauridae (Sauropterygia: Plesiosauria). PhD thesis. University College Dublin, 278pp.

Smith, A.S. 2013. Morphology of the caudal vertebrae in Rhomaleosaurus zetlandicus and a review of the evidence for a tail fin in Plesiosauria. Paludicola 9 (3): 144–158.

Smith, A.S. and Dyke, G.J. 2008. The skull of the giant predatory pliosaur Rhomaleosaurus cramptoni: implications for plesiosaur phylogenetics. Naturwissenschaften, 95, 975-980.

Smith A.S. and Benson R.B.J. 2014. Osteology of Rhomaleosaurus thorntoni (Sauropterygia: Rhomaleosauridae) from the Lower Jurassic (Toarcian) of Northamptonshire, England. Monograph of the Palaeontographical Society, London: 168 (642), 1–40, pls 1–35.

Written by Adam S. Smith

January 8th, 2015 at 12:58 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?]

New plesiosaur replicas for 2011

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A couple of new plesiosaur figures will be released in 2011, both from blossoming company CollectA. As a UK-based company CollectA has a tendency to choose British taxa, sometimes rather obscure ones. So forget Elasmosaurus or Kronosaurus, CollectA have gone out of their way to produce the first ever replica of two wonderful British Jurassic taxa: Rhomaleosaurus and Attenborosaurus.

Rhomaleosaurus was the subject of my PhD project so it’s fantastic to see it turned into a toy. I’ve written a full review of this figure over at the dinosaur toy blog (here)

Rhomaleosaurus CollectA

I’ve discussed my favourite plesiosaur Attenborosaurus here on the blog before, as I’ve been closely involved with the Trinity College cast (see previous posts here and here). Again, it’s great to see a more unusual taxon reproduced in toy form and I’ll review this figure properly soon.

Attenborosaurus CollectA

That’s it for new plesiosaur figures for 2011, but who knows what the future might bring…

Written by Adam S. Smith

March 22nd, 2011 at 7:01 pm

Naming Meyerasaurus – a guest article by Marc Vincent

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I’m pleased to present a guest article by journalism student Marc Vincent. The subject is the naming of Meyerasaurus, a topic that links in quite nicely with a previous post. Marc produced the article for his university course. The quotes from myself are the result of an interview Marc conducted as part of the project. I reproduce his article here as a slightly condensed version, enjoy!

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“In a German museum sits a remarkable fossil with an equally remarkable history. The exquisitely preserved remains on display in the Staatliches Museum für Naturkunde in Stuttgart belong to a plesiosaur – more specifically it is one of the short-necked pliosaurs, a clade (Pliosauroidea) that included the famous forms Kronosaurus and Liopleurodon. Mounted on the wall, its intricate underside exposed for all to see, sits Meyerasaurus victor – 3.35 metres long and dating from the Toarcian age of the Early Jurassic (180-175 million years ago).

Until this year however the animal wasn’t known as Meyerasaurus at all. For decades previously it was known as ‘Rhomaleosaurus’ victor, having thought to have been in the same genus as other, British pliosaur species since the 1960s. Before that it had been known as ‘Thaumatosaurus’ victor for fifty years. The generic name ‘Thaumatosaurus’ was coined by the German palaeontologist Herman von Meyer, but was based on inadequate material.

The British palaeontologist Richard Lyddeker later referred the Stuttgart pliosaur to the genus, which he considered to be the senior synonym of Rhomaleosaurus. However, it is rather likely that he simply rejected the name Rhomaleosaurus without consideration as it had been devised by Harry Seeley, a rival of his.

The referring of the Stuttgart pliosaur to ‘Thaumatosaurus‘ was innocently cemented by the German palaeontologist Eberhard Fraas when he described the specimen in 1910, following Lydekker’s work. The name ‘Thaumatosaurus‘ is today considered a nomen dubum but is still associated with the Stuttgart specimen in the minds of many palaeontologists – thanks to Fraas’ influence.

Unfortunately such a chequered history is common in the nomenclature of fossil animals. In the 19th and early 20th centuries, experts’ thoughts on what constituted a genus, or an order, were very different, so much so that almost every plesiosaur found was casually assigned to the genus Plesiosaurus (in the same way that countless predatory dinosaurs were assigned to Megalosaurus). Today, palaeontologists are slowly fixing the taxonomic muddle left behind by their forebears.

Dr Adam Smith, now Natural Science Curator at Birmingham’s Thinktank science museum, worked alongside Dr Peggy Vincent on a paper (four years in the making) that formally assigned the former ‘Rhomaleosaurus’ victor to the new genus Meyerasaurus.

Meyerasaurus is named after Herman von Meyer, who originally described the specimen. However, there is also an extinct lizard named Meyasaurus, and a dinosaur named Maiasaura, and they all sound remarkably similar when read aloud. Adam wanted to reinstate ‘Thaumatosaurus‘ with ‘Thaumatosaurus’ victor as the new type species, but he was barred by ICZN (International Commission on Zoological Nomenclature) rules.

“The specimen has always historically been associated with the name ‘Thaumatosaurus’ and I’d have liked to reintroduce that name to avoid as much confusion as possible. If you say ‘Thaumatosaurus‘ to most palaeontologists they won’t think of the type specimen, they’ll think of the ‘Rhomaleosaurus’ victor,” he says.

“When it was clear that we weren’t allowed to keep ‘Thaumatosaurus‘ due to ICZN rules, I wanted to introduce the name ‘Thaumatosaura‘ and feminise it, so at least we’d have the same name more or less. But also the species name is masculine, so the binomial name ‘Thaumatosaura‘ victor would have been confusing.”

In 2008 the journal Naturwissenschaften published a paper authored by Adam and Dr Gareth Dyke that included a fresh cladistic analysis of Rhomaleosaurus and related genera in the Rhomaleosauridae. They found that the genus Maresaurus separated the true Rhomaleosaurus species, including Rhomaleosaurus cramptoni, and what was then called ‘Rhomaleosaurus’ victor.

This was a problem as it made the genus Rhomaleosaurus paraphyletic, that is it united animals that didn’t belong together in a single genus, as they were too different. In addition to ‘Rhomaleosaurus’ victor, ‘Rhomaleosaurus’ megacephalus was also found to not be a true Rhomaleosaurus species. Clearly these animals required new generic names, and it was this that inspired the latest paper and the naming of Meyerasaurus victor.

What exactly Smith and Vincent determine to be the diagnostic characteristics of Meyerasaurus are laid out in full in the paper. They include the proportions of the limbs relative to the head and body – a graph in the paper dramatically illustrates the considerable difference in the relative lengths of the humerus and skull in Meyerasaurus and true Rhomaleosaurus – and also characters of the skull and palate.

Put simply, “[Meyerasaurus] has much larger limbs and a smaller skull relative to the body.” In addition, there are important details of the skull and palate bones (often used for diagnostic purposes in pliosaurs due to their frequently very incomplete remains) that, to Adam, indicate that Meyerasaurus deserves separation from Rhomaleosaurus.

With the reassigning of ‘Rhomaleosaurus’ victor to Meyerasaurus, there is no longer any overlap in plesiosaur genera in Early Jurassic Germany and Britain. This raises the question – why not? It is accepted that the region was united during the epoch, as it was almost completely underwater. It may have been a yet unknown geographical feature that kept these fauna separate – or they may have simply been separated in time.

Although the paper notes that more research is needed, Adam’s thoughts on the matter are quite clear. “We know that the deposits in Germany aren’t exactly the same age as the deposits in the UK, and so it seems that that’s the most likely explanation for the generic separation.”

Of course, he’ll also admit that taxonomy is a human invention and, by and large, distinctions at anything above specific level can be pretty arbitrary. “The only definitive level in taxonomy is the species level. There are some people that say even a species doesn’t exist and the only objective entity in biology is the individual, the actual physical individual – that everything else is just a hypothesis.”

“In some ways it doesn’t matter. All that matters is that it’s internally consistent and goes by the ICZN rules. As long as you know what you mean when you say the name Meyerasaurus that’s the important thing.”
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Written by Adam S. Smith

March 10th, 2011 at 11:37 pm