Eagle Ford pliosaur tooth prep

[pachy-pleuro-whatnot-odon]

Last year, on his final fossil hunt in North Texas, Tyler (@Mikrogeophagus) found a tiny sliver of pliosaur tooth sticking out from a piece of lower Turonian Kamp Ranch Limestone (Eagle Ford Group). Not knowing whether it'd be worth keeping the fragment, especially in light of his upcoming move, he graciously gave me the piece as part of a trans-Atlantic fossil exchange. It had long been my intention to see if I could prep the piece out a bit further, and, last week, finally got to it. And I must say, it was a struggle - but I absolutely love how it came out! US pliosaur teeth are so rare... and to now not only have a fragment of one in my collection, but, moreover, have invested so much effort into it myself, makes this a very valuable piece to me!

 

 

As I had seen others on the forum describe, I started off scraping and flipping off pieces of matrix with a penknife, though it quickly became apparent that this strategy wouldn't last me too long. The matrix was simply too hard for that. So I turned to another method I had already familiarised myself with in other prepation-projects: using a sturdy dental hook to push off bits of matrix - that is, more or less the same thing you'd do with an airscribe (which I, unfortunately, don't have), yet with more precision and control (if only perceived) by working by hand. Working under magnification the going was slow, as I wasn't just working a new type of matrix, but especially I didn't want to risk damaging this, to me, unique specimen - in particular because what makes these pliosaur teeth special is their beautiful and intricate pattern of striations. As I worked my way down from the top of the fragment, the going became increasingly tough, with me eventually only chipping off individual grains of sand, since the matrix turned out to become progressively calcitic. Even a strategy of cross-hatching the matrix before trying to pop bits off started yielding less and less results.

 

It was at this point that I decided I'd try out the Culiau Customizer I had received for my birthday last year but hadn't ever used. It's a light-weight but powerful USB-charged rotary engraver, and was, therefore, perfect for grinding some of the thicker matrix away with precision, to leave just a tiny layer to work off by hand. Additionally, even then, bits of matrix would sometimes not give way. And rather than try and force them off of the tooth with my dental pick or attempt to grind them away, I switched to locally applied acetic acid to weaken the bonding, if not outright dissolve, the sticky matrix. This whole process went on for about 9-10 hours in total, until I had found all edges of the fragment (which, at the base, is exactly where the root would've started, from tiny slivers of root still visible there). I then cleaned off the specimen, let it dry, and applied a layer of Paraloid B-72 to protect the tooth - something I had already occasionally been doing as I had worked my way down to prevent potential enamel loss or damage to the tooth by excessive force. And, let me tell you, the force needed to work through this was a lot! I entirely bent my dental hook out of shape twice! As said, however, I just love the result. And when I showed Tyler, he suggested I make this post to share it with you all!

 

So, without further ado, here it is!

 

 

Thanks again, Tyler, for this awesome fossil!

Edited Wednesday at 02:10 PM by pachy-pleuro-whatnot-odon

[mr.cheese]

That has turned out really well. I have a set of dental picks and haven't got round to using them yet, you have given me a bit of inspiration there. 

 

Very nice special specimen.

[Mikrogeophagus]

I've said it once and I'll say it again, this is terrific work! Really happy that guy landed in the right hands. Seems like that rotary engraver served you well too, so I am excited to what else you prep with it in the future!

[Ptychodus04]

Nice work. The Kamp Ranch matrix is definitely not one to tackle with hand tools.  The teeth usually prep well but a scribe is usually the best tool for the job. Acid prep is also a good route for this matrix, although one has to be careful here. Often, the teeth are cracked and held together by thin veins of matrix. Taking the acid prep too far can lead to a pile of tooth fragments. 

[pachy-pleuro-whatnot-odon]

15 minutes ago, Ptychodus04 said:

Nice work. The Kamp Ranch matrix is definitely not one to tackle with hand tools.  The teeth usually prep well but a scribe is usually the best tool for the job. Acid prep is also a good route for this matrix, although one has to be careful here. Often, the teeth are cracked and held together by thin veins of matrix. Taking the acid prep too far can lead to a pile of tooth fragments. 

 

Yeah, I experienced that first hand! 😅

 

Unfortunately, all I've got at home is a Dremel engraver, which I felt would be too rough for work this fine...! I also know completely what you mean with the thin veins of matrix that hold the tooth together. There's an example of that in this specimen too. Difficult to prep around, as I was afraid the crack might be unstable - luckily it wasn't.

 

I also used the acid prep only spot-wise, applying it with a cotton swab, so that its application could be finely controlled.

 

Anyway, great tips to take into account the next time I attempt a piece like this, as I think my hands and tools will be grateful for them...! 😅

[North]

Tooth seems to have nice details on it. 

Very nice.