Thursday, 18 February 2010

Prep Jobs for a Rainy Day

I love theropod teeth. There’s a beauty about them that provokes your imagination into overtime. For a start, in the right formation, they can be fairly commonplace. They vary in size, colour and shape and are often well preserved. It never fails to amaze me how amazing the enamel detail can be after millions of years have passed.

They are also much more intimate than bone. For me, when you pick up a tooth in the field, your mind instantly alerts you to the fact that this tooth was in a theropod mouth and undoubtedly aided the animal in killing its prey and for eating meat (and bone in some cases). The tooth was either shed during a meal or perhaps, when the animal died, became disassociated from the rest of the carcass. Yes, teeth, for me, are fascinating and they can tell us so much.

Because teeth, like all fossils, can be found in various states of preservation, they all represent different challenges when it comes to preparation and conservation. Take for instance the Daspletosaurus tooth in the image above and those that follow below. It’s unusual to find teeth of this size anyway, but this dentary tooth is exceptionally well preserved. Aside from some gentle pick work to remove matrix, light brushing and a gentle hand polish (with no solvents or chemicals I hasten to add), this tooth needed nothing in the way of restoration.

For conservation purposes though, the base of the crown and a few cracks were cleaned thoroughly and stabilised with a consolidant. But this really was as much as was needed for this tooth. Incidentally, this tooth was identified as Daspletosaurus torosus but I’m not so sure and have temporarily labelled this tooth as Daspletosaurus Sp. The superb serrations are tiny for a tooth this size – I’ve never seen anything like them before and am looking forward to studying the tooth in more detail.

These next teeth are also tyrannosaurid teeth, but this time from the Hell Creek formation in Montana.These are two teeth that were recovered in a disassociated state and highlights how different the challenges can be. The first example simply does not have enough substance to form a tooth again whilst the other went together reasonably well and, although there are obviously parts missing, it isn’t too bad a specimen for a reconstruction job. It could be restored a lot more if required but I prefer such teeth as they are and these are useful for comparative study.

This next image shows another example – probably a tooth from Tyrannosaurus rex, since this is from uppermost Maastrichtian deposits of Montana. This, on the face of it, is a fairly large tooth and there appears to be enough substance for a decent reconstruction. The fragments on the left of the image have been separated out because they all have a blue hue and should piece together as a base for the entire reconstruction. Being a large tooth obviously aids the rebuild. And then you get to the jobs for a rainy day – a very rainy day!

These next images show two dromaeosaurid teeth – probably Saurornitholestes. When teeth get this small, an enjoyable part of reconstruction can suddenly become a nightmare scenario. I mean, there’s fiddly and then there’s really fiddly, and fragments of these proportions are incredibly hard to work with. There is no immediate rush for these at the moment and it will have to rain very hard for me to consider working with them although they will be looked at eventually. If I had to make an evaluation of these two teeth now, I'd say the first tooth almost certainly does not have enough substance for reconstruction but the second tooth has a chance.

In any event fossil teeth, as well as fossil bone, in such a fragmentary state represent a significant challange to the preparator. A combination of both lateral and three dimensional thinking, as well as anatomical knowledge is required and, of course, a bit of luck is always welcome!


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