Fodonyx – a new genus of rhynchosaur

Yes my new paper is out (co-authored with my PhD supervisor, colleague and all-round-rhynchosaur expert Mike Benton) and as a result I want to talk about rhynchosaurs. OK, so they are not really dinosaurs, in fact they are not actually even archosaurs, but they are reptilian, lived alongside the dinos and are dead so they more or less count. And given what has passed for ‘dinosaur’ posts by me of late something on some other archosaurs seems appropriate. Besides, it’s not like you lot are going to stop me is it?

So rhynchosaurs then – the chisel lizards – so called because of their bizarre ‘tusks’ at the front of the jaws. These look rather like giant incisors and as a result give them a bit of a rabbit-like appearance, but these things aren’t teeth. In fact they are just modified jaw bones (the premaxilla above and dentary below) that in life would have stuck out through the flesh of the animal to form these pseudo teeth. In fact you can see marks on the bones where the skin would have stopped and the bony protrusion started.

Rhynchosaurs had a global distribution and have been found in North and South America, Europe, India and Africa. They are sprawling archosauromorphs that lived throughout the Triassic and were actually quite diverse and all things considered, relatively common. There is a general consensus that rhyncosaurs were basically pig-a-likes grubbing around for roots and tubers which they dug up with the strong legs and big claws and then chomped through with their tusks and grinding teeth. All in all, happy little reptiles, though some got quite large (2 metres or so) considering the times in which they lived.

My paper actually covers two major specimens – the first is an incomplete and partially articulated skeleton from the south coast of England (around Sidmouth for those who know where that is) and had sat around undescribed for I think about 10 years before I was ‘given’ it by Mike as part of my PhD thesis. I wanted to learn about writing a formal description and due to some complicating factors, this was the only thing available. Mike was quite happy that it belonged to Rhynchosaurus spenceri a very large rhynchosaur from the UK. However, Mike also had a small sandstone nodule with a pair or rhynchosaur lower jaws sticking out the end that had been found by a colleague in the same locality many years ago and left with him as it had, apparently, little value (jaws are common). For the sake of completeness it was decided that these should be prepared and added to the description.
The skull of Fodonyx spenceri
As it turned out there was a bit more to the jaws, and in fact there was a near complete skull in the nodule! This is one of the best known for rhynchosaurs with a complete palate, articulated jaws and much of the braincase still intact. Some find and far more than anyone anticipated when the work began (I should note that the preparation of the skull was done by Remmert Schouten at the UoB). So now we had a new skull as well as a good skeleton, and previously R. spenceri had been known from just a partial skull. Believe it or not the known pieces almost exactly match the parts missing from the new one, making restoration nice and easy.

It was clear that the new material was indeed R. spenceri – the size alone marks it out among European rhynchosaurs, but it was all from the same locality so referring the material was simple. However, armed with new information about the skull it was clear that the animal was quite distinctive and deserving of a generic name and was duly bestowed with ‘Fodonyx’ – the ‘digging claw’. I have mentioned themed names before and the rhynchosaurs are no exception as almost all members have a name that either contains ‘onyx’ (claw) or ‘rhynchus’ (chisel). Fodonyx is a bit naughty in that we have combined Greek and Latin roots in the name, but frankly that is very common now and is hardly a major crime.

Obviously the name we have given the animal refers to the prominent claws that are characteristic of rhynchosaurs. They are strong, long and deep though relatively narrow and actually quite flat (there is not too much curvature to them). Overall they do not look unlike those of other animals that are happy to scratch around on the surface, but are hardly adapted to digging and hence the inferences about rhynchosaurian lifestyles. One thing that is unusual is that the claws are rather better developed on the hindfeet than the fore. When we think of digging animals, it is generally the forefeet that do the work, though it appears that with rhynchsaurs they primarily dug with the feet rather than the hands.
Fodony foot
That more or less wraps it up for now. Fodonyx spenceri is now well represented with these two new specimens meaning that we pretty much have a complete skull, a fair amount of vertebral series, part of the pectoral girdle and an almost complete pelvic girdle and hindlimb as well as ribs gastralia and chevrons. It is now one of the most complete rhynchosaurs and certainly the best preserved in the UK. There is still more work to do, with some ongoing effort into restoring the skull with some groovy advanced scanning and casting techniques. So stay tuned.

This is a revised version of a Mk.1 post, to see the original with comments etc., go here.

10 Responses to “Fodonyx – a new genus of rhynchosaur”

  1. 1 Michael Downes 29/03/2010 at 2:09 am

    Hope it’s ok for me to quote you on my blog publicising the new season at Budleigh Salterton Fairlynch Museum in Devon, near where your rhynchosaur was found. See
    Best wishes

    • 2 David Hone 29/03/2010 at 8:11 am

      Yes Michael of course!

      Use what you want. Darren Naish’s website ‘Tetrapod Zoology’ has a good general review of rhynchosaurs and Mike Benton’s personal website at the University of Bristol holds a PDF of the paper too if you are looking for more info.


  2. 3 Debs 24/05/2012 at 8:12 am

    Would the stronger digging claws on the hind feet be because they dug into the sand to lay their eggs like turtles ? ( sorry I,m just an amateur )

    • 4 David Hone 24/05/2012 at 9:27 am

      Nothing wrong with being an amateur or asking questions! The short answer is probably not. Digging-like claws is not a common adaptation in reptiles, yet almost all of them lay eggs and many (including dinosaurs) had to dig nests. Obviously nest digging was a big thing, but yet huge numbers of species manage to dig appropriate nests without any specialisations at all (look at the feet of tortoises and turtles for starters) so why the rhynchosaurs would need this when others didn’t (including other reptiles living in the same time and place and trying to bury their eggs in the same soils) suggests that it’s for another purpose.

  1. 1 And thus was born a name… « Dave Hone’s Archosaur Musings Trackback on 28/06/2008 at 10:08 pm
  2. 2 Being eaten alive? Arrrrrgggggghhhhhh!!!! « Dave Hone’s Archosaur Musings Trackback on 05/11/2008 at 11:23 pm
  3. 3 Those rhynchosaurs again « Dave Hone’s Archosaur Musings Trackback on 30/01/2009 at 3:09 pm
  4. 4 Bonus rhynchosaur skeleton « Dave Hone’s Archosaur Musings Trackback on 22/04/2009 at 8:03 pm
  5. 5 Technical drawings « Dave Hone’s Archosaur Musings Trackback on 02/12/2009 at 8:29 am
  6. 6 Introducing Bentonyx « Dave Hone's Archosaur Musings Trackback on 02/12/2010 at 3:16 pm
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