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 from. As discussed in the open access paper (do take a look), the specimen is sufficiently different from all other pliosaurs to warrant a scientific name of its own, Pliosaurus kevani.
Pliosaurus kevani was named in honour of Kevan Sheehan, the Osmington Mills café owner who collected most of the skull, piece by piece, over a period of eight years during daily walks along the foreshore. Kevan collected chunks up to 60 kg in mass 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.
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 have a pretty accurate reconstruction of Pliosaurus. On the basis of this reconstruction I’ve also had a go at restoring the life appearance of the head of P. kevani in profile. Despite its large size and massive teeth, the head is rather gracile.
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 had done in the Early Jurassic. The paper also discusses the evolution of pliosaurids. The earliest thalattophoneans have a long mandibular symphysis, but in later member it 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.
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 aspects of the morphology in 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 (P. funkei, also known as Predator X, P. brachydeirus, P. rossicus, there might be one or two more, pending thorough description of the material) and we find ourselves with a rather large number of species within a single genus (although some invalid species of Pliosaurus are 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.
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.
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.
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.
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?]
There was a time when I’d leap into tippy-tappy action at the first sniff of a newly named plesiosaur. Unfortunately, I haven’t been keeping Plesiosaur Bites up to date and a few new taxa have passed me by. Of course, when I say “a few”, what I really mean is we are swamped by the things. Little wonder I haven’t been able to keep up.
A few years ago I plotted a graph in my PhD thesis (Smith, 2007, Figure 2.2.) to show the number of valid plesiosaur species and genera named in successive 20-year time intervals since 1821 (when the first plesiosaur was named [Plesiosaurus]). The data ended in 2007, the year I submitted my thesis, but showed that new taxa were being erected at a relatively steady rate throughout the 19th and 20th century (Figure 1). The rate started to pick up during the 1990s and I extrapolated the data into 2008-2020 based on the first seven years of the 21st century. I predicted 30 new genera in the period 2001-2020, which would represent a huge post-2001 leap in the number of new valid plesiosaurs. Well, so much for my crude calculations. It’s only 2012 and my ‘huge’ prediction has already been surpassed.
Figure 1. Tally of the number of new plesiosaur taxa per 20-year interval (from Smith, 2007, Y-axis adjusted for direct comparison with Figure 2 below). 2001-2020 predicted based on 2001-2007 data.
An adjusted prediction for 2001-2020 based on the average rate of new taxa from 2001-2012 is actually pretty staggering (Figure 2). 62 new species and 51 new genera in a 20-year period? Can this be right, or are we about to reach a major drop off – were the last two years just out of the ordinary? Time will tell, but there are no signs yet of the bombardment slowing down, and if my previous prediction is anything to go by, the figure could even be an under-estimate.
Figure 2. Adjusted plot, with the 2001-2020 prediction based on 2001-2012 data.
So, how many plesiosaurs have been actually been named since 2008? Here’s a summary of all the new additions so the group:
Nichollssaura, Gallardosaurus (2009)
Meyerasaurus, Alexeyisaurus (2010)
Abyssosaurus, Westphaliosaurus, Hauffiosaurus tomistomimus, Marmornectes, Zarafasaura (2011).
Albertonectes, Anningasaura, Avalonnectes, Cryonectes, Lusonectes, Djupedalia, Dolichorhynchops tropicensis, Eoplesiosaurus, Pliosaurus funkei, Spitrasaurus wensaasi, Spitrasaurus larsoni, and Stratesaurus (2012). So far.
Presuming I haven’t missed any (and please let me know if I have), that’s 22 new binomial taxa in the space of five years: 18 new genera and 21 new species (I’ve only listed the new species names above where they belong to existing genera, or where two new species have been erected within a new genus). I think this significant increase is due to several factors.
Firstly, historic plesiosaur specimens are receiving a considerable amount of renewed research attention. Many of the new taxa are based on fossils excavated in Victorian times. Anningasaura, Avalonectes, Eoplesiosaurus, Lusonectes, Strateosaurus, all fall into this category. Plesiosaurus continues to be exposed as the waste basket taxon it is.
Secondly, there have been numerous new discoveries in recent years. Sometimes these are the result of chance. Sometimes they are the result of a positive relationships that have developed between collectors or mining/quarrying businesses and palaeontologists. But often they are due to dedicated efforts to explore new strata or geographical areas. Djupedalia, Pliosaurus funkei (‘Predator X’ and ‘The Monster’), Spitrasaurus, and Zarafasaura, come to mind here.
Finally, more palaeontologists are looking at plesiosaurs in general. With fresh eyes. We are seeing differences where we weren’t even looking before, we are examining specimens more closely and more critically, we are applying new techniques and technologies to gain a greater understanding of plesiosaur anatomy, biology and phylogeny. It is inevitable that as more of us look, and as we look in more detail, we begin to unravel the complexity and diversity within Plesiosauria. Similar things are also happening in ichthyosaur research and mosasaur research, and I fully expect this ‘Mesozoic Marine Reptile Renaissance’ to continue into the foreseeable future. I’m looking forward to what the future holds in the world of plesiosaurs, even if I am struggling to keep up. One of these days I might even get around to writing about some of these new taxa and adding them to The Plesiosaur Directory…
Smith, A. S. 2007. Anatomy and systematics of the Rhomaleosauridae (Sauropterygia: Plesiosauria). PhD thesis. University College Dublin, 278pp. (Unpublished) (download PDF – 12.5mb )
Most museum collections contain hidden treasures, but the Honington plesiosaur in the Warwickshire Museum is one treasure, I’m pleased to say, that is no longer hidden.
I first came across the Honington plesiosaur while working in the geological collection of the Warwickshire Museum under the supervision of Jon Radley, the curator of natural sciences. While in the stores, my beady little eyes couldn’t help but spot the neatly printed name, ‘Plesiosaurus rugosus’, on an unopened dusty box. Upon further inspection we discovered, to our astonishment, an almost complete long-necked plesiosaur skeleton. I took the time to lay out the remains and after a little digging through documentation, we were able to confirm that the specimen originated from Honington, near Shipston-on-Stour, in Southern Warwickshire. The fossil is also well-constrained stratigraphically, which is quite rare for historical specimens of Lower Jurassic plesiosaurs.
The specimen consists of an almost complete postcranial skeleton, but unfortunately lacks any trace of the skull, as is often the case in long-necked plesiosaurs. This is partly because the small skull in plesiosauroids is delicately constructed and prone to damage. Despite the missing cranium, the specimen is noteworthy because it is preserved in three dimensions and is free from matrix. This means it is possible to view and study the bones from all directions and gather proportional data.
Jon and I are in the process of writing up a description of the specimen and assessing its identity and evolutionary significance. In the meantime, the Honington plesiosaur has quite rightly wriggled its way out of storage and onto public display. It’s now exhibited in a beautiful case as part of a recently renovated gallery. I was happy to be able to assist with the Honington display and provided a life-restoration of the animal as a graphic to accompany the new display. A resin replica of a skull representing Plesiosaurus is doing a fine job as a replacement for the missing cranium. The fossil also makes a fitting counterpart to another spectacular marine reptile on show in the gallery, the Wilmcote plesiosaur – a beast for a future blog entry perhaps? So if you’re in the region, do drop in!