Tuesday, December 17, 2013

Jaw Fragments and Shoulder Girdle

Jaw Fragments and Shoulder Girdle

We have for your viewing pleasure a couple of unrelated items. Back in July I posted about a jaw fragment with teeth that we found. We now have a second jaw fragment, with tooth sockets. These two jaws are not from the same type of animal. In one, the teeth are in separate sockets  - called "Thecodont". The other, the teeth (now missing) are in a groove with equal sides - called "Aulacodont".

The Aulacodont is most typical in Ichthyosaurs except for the Triassic varieties of Shonisaurus and Cysbospondylus which are Theocodont. The giant amphibians have teeth that are in individual sockets - Theocodont. So who's jaws do we have above? 

The skull we have, amphibian, has teeth present but the details of the jaw are not clear since they haven't been prepared yet. The teeth in the jaw look like the teeth in the picture above.  So I'm betting the jaw fragment with teeth belong to the amphibian, and the jaw with the groove is from the Ichthyosaur. This contradicts my posting of July 26th where I thought we had the Ichthyosaur jaw. We keep learning new things and finding new bones all the time with this specimen! 

As a second item, we have now fully prepared what looks like a Scapula. Previously we had two bones that I believed to be Coracoids. We also have a humerus, or upper arm bone. We can fit all four bones together as they would have been in life. This scapula is thick at the part where all three bones fit together (the Glenoid Process) where the limb rotates. Otherwise, it is very thin about 1-3mm thick. This bone required a full plaster backing to complete the preparation. It came out very nicely - a great bone!. 

 We are still missing the clavicles (collar bones) but one bone is a strong candidate. 
We'll have it out in a couple of days so we should be able to see if it really is a clavicle. 

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