It might not be well known outside of palaeontology that the south-west of England is famous for its marine reptile fossils. But it is: some of the best, most historically significant, plesiosaur and ichthyosaur specimens have come from Street in Somerset and from Lyme Regis and Charmouth in Dorset.
These rocks - spanning the Triassic-Jurassic boundary and known collectively as the Lower Lias - yield the giant, robust-skulled ichthyosaur Temnodontosaurus, the swordfish-like Leptonectes and Eurhinosaurus, and the more familiar, dolphin-like Ichthyosaurus. The long-necked plesiosaurs Plesiosaurus, Archaeonectrus, Thalassiodracon [shown below] and Attenborosaurus also come from these rocks, as does the short-necked plesiosaur Eurycleidus. Many of the specimens are beautifully preserved, and their discovery during (and even before) the early 1800s meant that they played centre-stage in debates on the diversity of vanished life (Howe et al. 1981, Taylor 1997).
If you're interested in Mesozoic marine reptiles such as these, on the faunal changes that occurred across the Triassic-Jurassic boundary, or on the role that fossil marine reptiles have played in the development of palaeontological thought, you'll be very interested to know that a special Palaeontological Association seminar devoted entirely to these subjects is being held at Street in Somerset on Friday July 31st 2009. While the talks presented during the seminar will review current knowledge of Lias geology and palaeontology, it is hoped that new data and discussion will also characterise the meeting: some details of the stratigraphy are still controversial, and the taxonomy and affinities of some of the animals remain disputed or require further study.
The meeting is titled Sea Dragons of Avalon: the early radiations of the marine reptiles and recovery from the Triassic-Jurassic faunal crisis, with special reference to Street in Somerset and the wider British record [the meeting logo is shown above]; it's followed on August 1st 2009 by a fieldtrip to local quarries and other areas of interest. Prior to the seminar itself - on Thursday 30th July - world-renowned ichthyosaur expert Dr Ryosuke Motani is giving a talk entitled 'Street's town symbol: the ichthyosaur two centuries since its discovery'. For the duration of the meeting we will have posters and fossils on display, and we also plan to visit the Alfred Gillett Collection of local fossil reptiles (thanks to the kind courtesy of the archives of the Alfred Gillett Trust) [just to remind you how neat ichthyosaurs are, here's that cladogram again. It originally appeared back in June 2008].
For further details on the meeting please see the Palaeontological Association page here; a programme, with speakers and talk titles, is available here, and the booking form is here. Any enquiries about the meeting can be sent to street2009@palass.org.uk. A great line-up has been arranged, and this is sure to be a great meeting. I hope to see you there!
Ref - -
Howe, S. R., Sharpe, T. & Torrens, H. S. 1981. Ichthyosaurs: a History of Fossil 'Sea-Dragons'. National Museum of Wales, Cardiff.
Taylor, M. A. 1997. Before the dinosaur: the historical significance of the fossil marine reptiles. In Callaway, J. & Massare, J. (eds) Ancient Marine Reptiles. Academic Press (London), pp. xix-xlvi.
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I really wish I could attend this meeting. The marine reptile faunal change is a very interesting topic. (Bakker 1993) Had a paper on plesiosaur extinction events, evidently he thinks plesiosaurs in the cretaceous are not related to the jurassic forms. Instead he feels that they derived from Pliosaurs. The faunal change is indeed a very fascinating topic why for instance did icthyosaurs and the gigantic pliosaurs go extinct way before the KT event? In summary it is good to see the ancient marine reptiles getting more attention in recent years.
Will there be cake?
Is there a version of that icthyosaur cladogram big enough for the names to be readable?
Put some fur on the biggest one and it would look an awful lot like Trunko...
Yeah, I need a bigger copy of that picture, too. It would make an excellent desktop. Who's that snake-tailed form right below Shonisaurus
Hey Darren. I'd be part of it, just need to finish my poster!
? I thought you now able to imbed enlargeable images...
Well, no great matter-hope the conference goes well.
Hi all, thanks for comments. Zach: the long-tailed animal is Besanosaurus, see the previous comment here.
As for providing a larger version of the image, even enlargeable images (like the kingfisher case photo) are limited to 500 px, and the version above is 490 px and hence not much different. If you really want a full-size version, email me and I'll send it.
Wow, I'll definitely be there, thanks for the heads up Darren!
IT'S A DRAGON!!!
Shouldn't that be 1981..?
Mostly because of the Cenomanian-Turonian boundary mass extinction...
...though Brachauchenius survived it by a couple of million years and then died out.
David M wrote:
|Mostly because of the Cenomanian-Turonian boundary mass |extinction...
|...though *Brachauchenius* survived it by a couple of million |years and then died out.
Indeed; Schumacher and Everhart (2005) state that the youngest fossils of *Brachauchenius* [How do I do italics in this thing?] are early Mid-Turonian. There is also a large pliosaur specimen (maybe *Brachauchenius*) from Turonian of Japan (Kaim et al. 2008).
Dunno about the ichthyosaurs, but there were some big lamniform sharks(*Cretoxyrhina*) around in the Coniacian-Santonian (Shimada 1997). Did they outcompete the big pliosaurs.. or just replace them after the Mid-Turonian?
Kaim, A., Y. Kobayashi, H. Echizenya, R. G. Jenkins, and K. Tanabe. 2008. Chemosynthesisâbased associations on Cretaceous plesiosaurid carcasses. Acta Palaeontologica Polonica 53(1):97-104.
Schumacher, B. A., and M. J. Everhart. 2005. A stratigraphic and taxonomic review of plesiosaurs from the old "Fort Benton Group" of Central Kansas: a new assessment of old records. Paludicola 5(2):33-54.
Shimada, K. 1997. Paleoecological relationships of the Late Cretaceous Lamniform Shark, Cretoxyrhina mantelli (Agassiz). Journal of Paleontology 7(5):926-933.
It would be nice to see more studies done on the Cenomanian-Turonian extinction event(just learned something new). Are the marine reptile extinction events caused by species outcompeting each other? What is puzzling is why icthyosaurs which are so adapted to a marine life, to the point that their body morphology became baupin. A baupin design surely would have been a successful one in the marine realm(Ellis 2003). Did plesiosaurs survive longer due to different feeding strategies over icthyosaurs? What is even just as curious is how Mosasaurs end up taking over the top niche in the cretaceous seas(Everhart 2005). It would indeed be good to see more studies done on marine repile extinction events.
If sharks or mosasaurs outcompeted the pliosaurs, we would expect the "pliosaurian" ecological niche and the associated type of animal to disappear. However, this did not happen; other plesiosaurian clades like the polycotilids quickly evolved into something that was very similar to the recently extinct pliosaurs. *Dolichorhynchops* or *Trinacromerum* looked pretty much like small pliosaurs, and judging from their anatomy, their ecology and behaviour must have been rather similar. Such animals clearly could exist and even thrive in shark-, *Xiphactinus*- and mosasaur-infested waters, in spite of being rather small and vulnerable.
I wish some of these critters were still around (Nessie notwithstanding). How cool would that be?
This thing is HTML, so you put <i> in front and </i> behind it. The other tag you're looking for is <blockquote>.
No -- mass extinction events, global, land and sea, vertebrates and plankton, everything.
I agree that all of the smaller mass extinction events are understudied (and most of the big ones, too).
What do you mean? Is there some confusion with the German word Bauplan, "building plan", which is sometimes used in English for the basic groundplan of an organism's anatomy?
It's possible that they survived (or some of them at least) because they didn't feed in the same places. Many ichthyosaurs were deep-divers, judging from their humongous eyes, and probably ate lots of cephalopods (indeed, some have belemnite hooks as their fossil stomach contents). Now, the Cenomanian-Turonian mass extinction came with an Oceanic Anoxic Event, which means that all the oxygen disappeared from the sea except for the uppermost layers. No cephalopods in the deep sea, no ichthyosaurs. Or something. Maybe.
Matt,
I'm about to begin a thesis on the biodiversity and extinction of Cretaceous Ichthyosaurs, starting this october if everything goes allright! So more to come in a few months!
But I can say that the Cenomanian-Turonian boundary (CTB) was more severe than previously thought: I ve found some new species within the Albian of SE France, and they seem to have adapted to different food ressources than "conventional" Platypterygius suggesting an higher diveristy, at least during the Albian.
I'd hesitate to say that polycotylids are filling the same niche as Brachauchenius [thanks, David], which was an approximately 1 to 5 tonne apex predator with a large and robust feeding apparatus. It constitutes a pretty good candidate for the apex marine predator of the Cenomanian to lower Turonian. Polycotylids are smaller than this (although I'm not sure if any quantitative estimates of body mass hacve been made for them) and have a skull that is quite different (in terms of the functional morphology believed to indicate feeding ecology). Maybe the big sharks or mosasaurs replaced brachaucheniids ecologically, but I doubt that polycotylids did.
(Admittedly, however, the original point specified only pliosaurs, not necessarily large pliosaurs, but David did specifiy Brachauchenius, which is the last of the >1 tonne brachaucheniid/pliosaurid type pliosaurs known in the fossil record. Obviously, polycotylids, and elasmosaurids survived the Turonian, but they were unlikely to have been apex predators.
Is there any evidence of freshwater plesiosaurs and ichtyosaurs?
David,
In answer to your question about the baupin body plan. It is the specialized body plan where jurassic icthyosaurs devolped a body plan similar to a dolphin. Where as other marine reptiles(plesiosaurs, mosasaurs) didn't ever achieve this body form. However late Cretaceous Mosasaurs(plotosaurines)were (icthyosaur-like) but did not have the morphological form of the jurassic icthyosaurs. Mosasaurs may have been filling in the ecological roles left over by icthyosaurs.
Johannes,
The Polycotilid plesiosaurs although were traditionally classified as true pliosaurs are now considerd a sister taxon of the elasmosauridae(Bakker 1993, Carpenter 1996). They were dolphin sized, where the late jurassic and early cretaceous pliosaurs(Liopleurodon, Kronosaurus) were 30 to 50 ft long. So one of the remaining large pliosaurs to survive was Brachauchenius.
Valentin,
I look foward to reading your icthyosaur paper. I would like to learn about the icthyosaur fauna you are researching in SE France. So far most of our N. American Icthyosaurs come from the Late Jurassic Sundance Formation and the Middle Triassic Favert Formation. Not to mention the giant one from British Columbia. I admit I need to learn about ichtyosaurs. At the moment I'm doing projects on plesiosaurs and mosasaurs. So far this discussion has been very good! Thanks for the great post Darren
Yes, but remember that Bakker and Carpenter differed in where they placed the postulated elasmosaurid+polycotylid taxon - Carpenter (1999) thought them to be plesiosauroids, whilst Bakker (1993) thought that they were pliosauroids. In any case, this claim has been the subject of several analyses in the last decade. O'Keefe (2001) found that polycotylids were plesiosauroids and a sister taxon of the Cryptoclidids/Cimoliosaurids, with elasmosaurids more distantly related to these. Druckenmiller (2006 - see also Druckenmiller and Russell 2008) found the Polycotylidae to be pliosauroids (i.e. not closely related to any of the traditional plesiosauroid groups), most closely related to Leptocleidids - hence his group Leptocleidoidea. Ketchum (2008) also found a close relationship between the Polycotylidae and the Leptocleididae, but instead of these being pliosauroids her results indicate that the Leptocleidoidea are plesiosauroids, most closely related (as with O'Keefe's analysis) to the Cryptoclidids and Cimoliosaurids. Most recently, Smith and Dyke (2008) have also recovered the Leptocleidoidea (Leptocleididae + Polycotylidae) as the sister group of the Pliosauridae, i.e. as pliosaurs in the traditional sense. What can we conclude form this? The phylogenetic affinities of polycotylids are far from certain; they seem to be closely related to leptocleidids (not a new idea - Arthur Cruickshank was saying this when I first met him in the mid-90s), but hypotheses of their higher level affinities are not stable at present.
Maximum length in Liopleurodon ferox is 5-7 metres (roughly 16-22 feet). Maximum size in both species of Kronosaurus is approximately 10.5 m (34 feet). The largest pliosaur specimen known from anything like decent material is the Cumnor mandible, which Darren has blogged on before and which I estimate as belonging to an animal about 13 m (42 feet) long (McHenry 2009). Claims of pliosaurs larger than this size are based upon very fragmentary material and are therefore not particularly reliable, although that situation may change when the results of the work on the Svalbard pliosaurs are published.
Bakker, R. T. 1993. Plesiosaur extinction cycles - events that mark the beginning, middle, and end of the Cretaceous. Geological Association of Canada Special Paper 39:641-664
Carpenter, K. 1999. Revision of North American elasmosaurs from the Cretaceous of the Western Interior. Paludicola 2:148-173.
Druckenmiller, P. S. 2006. Early Cretaceous plesiosaurs (Sauropterygia: Plesiosauria) from northern Alberta: palaeoenvironmental and systematic implications. PhD Thesis, University of Calgary.
Druckenmiller, P. S., and A. P. Russell. 2008. A phylogeny of Plesiosauria (Sauropterygia) and its bearing on the systematic status of Leptocleidus Andrews, 1922. Zootaxa 1863:1-120
Ketchum, H. F. 2008. The anatomy, taxonomy, and systematics of three British Middle Jurassic pliosaurs (Sauropterygia: Pleiosauria) and the phylogeny of Plesiosauria. Unpublished Ph.D. Thesis. University of Cambridge.
McHenry, C. R. 2009. Devourer of Gods: the palaeoecology of the Cretaceous pliosaur Kronosaurus queenslandicus. Unpublished Ph.D. Thesis, University of Newcastle.
Smith, A. S., and G. J. Dyke. 2008. The skull of the giant predatory pliosaur Rhomaleosaurus cramptoni: implications for plesiosaur phylogenetics. Naturwissenschaften 95(10): 975-980.
Thanks Colin, great stuff. The aforementioned post on the Cumnor mandible is here. And, some time, I must publish more of my pliosaur stuff.
Colin,
Thanks for the update on the Polycotilids, they indeed are a confusing group of plesiosaurs when it comes to phylogenetics. Hopefully their systematics will be straightend out before too much longer.
I didn't know the size for Liopleurodon ferox is now considerd 16-22 ft. I knew Walking with Dinosaurs had it way too big, I was going on it's size from the Sea Dragons book that Richard Ellis wrote. Like you I'm fascinated by Giant Pliosaurs, and it's ashame they are known from mostly fragmentary specimens. These are huge predators which are even bigger than most theropods and have the bite force to match. They deserve more attention from the public than what they get.
I was also wondering if I could get a copy of your Thesis on Kronosaurus? I'm in the midst of a plesiosaur project that your paper would greatly help out with. Again thanks for the update on polycotilid systematics. It is always good to learn something more about plesiosaurs.
I've seen statements like this a fair bit recently. Are there actually any published estimates of bite force in pliosaurs relative to therapods?
Sure; just email me directly.
I understood what body plan you mean; my question was where you got the word "baupin" from.
Because, you see, I've never encountered it before. Googling for "baupin -denis -marcel -nicolas -dominique -douglas -anthony -coralie -delanoe -christian -vert -chantal -maire -politique -chloe -michel -geraldine" still finds 2170 results, of which the first and the 10th page of results still contain only the French surname Baupin.
So I wondered if you had drastically misread and misunderstood "Bauplan". I still think that's the case, because I can't make any other rhyme or reason of it.
Also, as I told you, it's "ichthyosaur", with chth. It's also "polycotylid".
Cimoliasaurids :-)
Indeed. Nor can I spell 'theropod'... :-)
I'm going to have to miss this meeting, which I'm really annoyed about as it's right up my Street (ho, ho).
Polycotylids are a bit of a problem in phylogenetic terms as Col has explained. There's certainly a huge morphological gap between them and the cryptoclidids and "cimoliasaurids". Homoplasy seems rife in the Plesiosauria with the "same" characters popping up all over the phylogenetic tree. Hopefully the description of more basal polycotylids will help to sort things out.
BTW Colin, I love the title of your thesis.
At the top-right of that cladogram I saw what I thought was a very unusual shape of ichthyosaur indeed, which I had never seen before, and was about to get all excited when I realized.. oh.. it's just drawn as if twisting to face the viewer. Not shown in profile like the rest.
This kind of thing is unfair, I reckon. Aren't there laws against online images not being clear enough at first (cursory) glance to not falsely raise (momentary) expectations of exciting animal weirdness?
Ah, it's a cruel world..
;-)
Regarding the Cumnor mandible:
I think that we need to treat it with some caution. If you look at it closely, you can see that a lot of it is plaster and wood. It isn't possible to determine how much is orginal or the original size without either CAT scanning the specimen - and there aren't many scanners big enough to fit it - or taking it to pieces and finding out which parts are original and which are reconstruction.
It looks to me as if it is a crushed and somewhat "smeared" specimen, and that the posterior part of the jaw has been reconstructed at it's smeared height, which is a fair bit higher than its original state. Looking at the jaw itself, I can't see any continuity of bone along the mandible which supports the reconstructed overall length. This leads me to think that the size has been extrapolated from the unreliable height of the coronoid process, and that the original length was probably a meter or so shorter.
This is still a very big animal and much the same size as the Westbury pliosaurs, though it's worth noting that it is not Pliosaurus.
Yes, there is also a large pliosaur specimen from Turonian of Japan
[url deleted, stop spamming]
These are huge predators which are even bigger than most theropods and have the bite force to match. replica uggs