Thursday, 26 January 2012

Prep News

A brief post this week and, again, featuring the continued preparation of our Oxford Clay plesiosaur. I’ve frequently mentioned the issues that have been encountered when comparing specimens from our animal with those in other institutions and the sometime extreme differences in morphologies of the same elements.

We are lucky, in one way, in as much as we have multiple associated elements from one animal and yet we have struggled to identify this specimen, although we have now almost certainly identified this plesiosaur to genus level. But with individual elements, or even parts of larger bones, you can have much tougher problems with identification. Sure, there are elements which can be assigned to, say, a plesiosaur or ichthyosaur but generic identification is problematic.
But specific isolated elements can also be equally diagnostic although I have found the identification of some marine reptile bones to be particularly challenging. For example, plesiosaurs increased the amount of phalanges in their limbs considerably over what is regarded as the standard plesiomorphic condition. This is known as hyperphalangy and is characteristic of plesiosaur limbs.
Phalanges all look alike and found in isolation are not particularly helpful although some of the bigger ones are obviously pliosaurid in origin. In contrast some other elements can often be identified to generic level and cryptoclidid humeri are particularly useful in this respect. It’s interesting that there are almost certainly odd elements in collections all over the world that not only represent missing elements from known taxa but also unknown elements from unknown taxa.  Again, Spinops comes to mind.
That aside, here are a set of proximal carpals from our plesiosaur all finished with and prepared. These are, from left to right, the ulnare, intermedium and radiale and are from the same forelimb featured in previous blog posts and I am now working on the distal carpals. After that, there are the first five metacarpals to prepare and then this particular forelimb will be finished – the remaining part of the limb has long since vanished. Shortly after I will publish a brief description and then this particular project will be temporarily shelved because of other projects but eventually the next element up for preparation is a rather impressive femur and, of course, I will publish posts along the way.

Ventral view

Dorsal view

2 comments:

Anonymous said...

Hi Mark my name is Darren Withers . Have we both met at Must Farm Clay Pit in Whittlesey . Searching for Marine Reptiles around Bed 10.

Mark Wildman said...

Hi Darren. Yes we've met a few times before - glad you've found the blog!

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