Wednesday, 29 June 2011

Prep News

I finally managed to finish off the prep work on the pliosaur vertebra that I blogged about here. At that point I had more or less finished working on the centrum and had begun work on the neural arch and the remnants of the processes. I was aware just how rare this vertebra was since dorsal vertebrae of pliosaurs are hardly ever found uncrushed in the Oxford Clay and to have one in three dimensions with intact neural canal and processes is unheard of.

Preparation was, however, remarkably similar to working on the centrum. A painstakingly slow process removing matrix piece by piece, almost particle by particle, was followed. Only occasionally did I have the luxury of being able to mechanically remove one or two stubborn spots of matrix with no fear of damage to the specimen.

Although the bone was well mineralised and robust, the surface of the bone could be easily chipped in places if you were not careful. This was especially apparent when cleaning out all the nooks and crannies that were formed during fossilisation as extreme pressures distorted the bone and the cracks that resulted filled with matrix and slowly widened. Every pore of the bone had clay or other matrix in situ and this was prised out speck by speck. These areas were consolidated with Butvar B76 as I went along.

The neural canal itself was the longest job of all. The vertebra had been distorted so that the neural canal was not only compressed mediolaterally but also angled between 5° and 10° rostrocaudally, and this made cleaning out the canal particularly awkward. Removing the bulk matrix from the canal did not pose any particular problems but the finer preparation did, as I struggled to work in a tight enclosed canal with both magnification and light impaired.

Eventually, though, the canal was virtually clear of matrix and I was surprised at how big it was and how deep it ended up, as it plummeted ventrally into the centrum. The rest of the processes were more or less straightforward with only one or two areas of stubborn resistance. Once the prep had been finished, the specimen was gently cleaned and a final coating of consolidant finished the job.

To be honest, there are bound to be a few specks of matrix in situ, especially in the neural canal and I’m sure that I could probably keep on prepping the bone but I am happy that the vast majority of it is fully prepared and that the specimen is complete.

There are many projects still in the pipeline just now and I am particularly keen to start work on an impressive hadrosaur dentary but, the immediate plan is to start work on some associated plesiosaur material that I’ve already alluded to in earlier posts beginning with the stunning humerus pictured below.

As can be seen, this particular bone is virtually complete and is broken in two pieces but the join is excellent suggesting that the fracture has only occurred recently. Preparation would appear to be straightforward although both the proximal and distal ends are somewhat encrusted with shell debris and detritus.

The bone, again, is heavily mineralised and dense and the join will need to be exceptionally strong. To support the bone will require a small purpose built cradle which will needed to be constructed for the task and this will also serve the dual purpose of providing the permanent storage case for the specimen when it is finished.

After the humerus there will be a lot of the other bones from the same forelimb to work on including the radius, ulna, and a host of other associated bones. These too are all well preserved and there appear to be no obvious complications. I will detail these bones as I go along and post periodic updates.

The pliosaur vertebra - as found


Anonymous said...

How does one distinguish a pliosaur vertebra from any other old vertebra?

(Sorry, this is probably a dumb question to you. I'm just a high schooler trying to educate myself in vertebrate paleontology. ^^; )

Mark Wildman said...

Firstly, it is NOT a dumb question! Don't ever think that it is and don't ever be afraid to ask. I do it all the time otherwise how would we ever learn?

Secondly, vertebrae come in all shapes and sizes and we all have trouble identifying them from time to time. There are cervicals, dorsals, sacral and caudal vertebrae to consider and, in this formation, they come from plesiosaurs, pliosaurs, ichthyosaurs, marine crocodiles and even, on rare occasions, from dinosaurs.

On this occasion, the sheer size of the vertebra was enough to identify it as pliosaur straight away since most of the plesiosaurs here are small to medium sized. The presence of nutrative foramen near the keel of the centrum confirmed it. I then had to look through the literature for descriptions and images before I could, with a high degree of certainty, say it was from Liopleurodon.

Anonymous said...

I am glad you understand; I run into tons of people that seem to be annoyed whenever I ask questions.

Thank you for the information. Hopefully I may be able to use it someday.

Mark Wildman said...

Anytime - and keep asking those questions. Good luck!

Post a Comment