Posted: Feb 28, 2010 2:10 pm
by theropod
Again, this posting is a part of the series once posted on that other bastion of rational thought.

In an earlier post I placed the following questions as a challenge to a fellow member that seemed to think his field of study surpasses all others and those without his exposure and learning were somehow a part of the "great unwashed". Since said poster feels this challenge was "silly" I feel it is my responsibility to provide answers to those which may be curious.

theropod asked;
1. What methods should one employ to ensure the long term preservation of an Edmonotosaurus annectens femur with advanced pyrite disease?

Pyrite disease is a nearly unstoppable degenerative condition wherein a fossil will eventually be consumed by replacement of the fossil material with pyrite crystals. While it is possible, with extremely tightly controlled storage, to slow, or limit, the advancement of this condition no means exists to completely halt the progression of loss. The best method to deal with this situation is to make a mold of the fossil and cast a replica. This condition is far too common in some depositional settings such as the Hell Creek formation, and those working with these fossils are fully aware of this fact.

theropod asked;
2. When one is confronted with a series of dinosaur fossils that are jumbled and cross bedded in close proximity to one another, and the matrix is a soft mudstone, what methods should one use to assure a limitation of damage during recovery?

When faced with such a situation the worker, or team of workers, should form a plan of action to ensure that the fossils do not become destabilized as a result of removing too much of the matrix in the field. Undermining the fossils by removing too much matrix can lead to collapsing trauma. Supporting material, such as wooden slats or steel bars, can be applied to individual fossils in a manner to add strength and form "bridging" structures. Judicial application of consolidants in conjunction with the supporting material will help limit recovery damage. A separating layer of material is applied between the fossils and the jacketing material so that the jacket does not adhere to the fossil and make final prep work a nightmare. When the jackets are formed, usually plaster or fiberglass impregnated burlap or other suitable material, on the upper surfaces of the fossils lifting hooks can be formed. These "strong points" will later serve as a means by which the fossils can be manipulated for transportation. Such jackets of multiple fossils can become quite large and unwieldy and consideration for final transport should be taken.

When the upper side of the jackets have hardened, and the fossils can be safely undercut to form a pedestal, the mass of fossils may have additional reinforcing material driven or otherwise placed beneath the fossils and matrix prior to being turned and the jacketing material fully encapsulating the fossils.

theropod asked;
3. Under what conditions is the use of acid reduction appropriate in the preparation of a fossil specimen, how does one make such a determination, and how does one determine the correct chemistry to employ?

Sometimes the matrix encasing a fossil is far too hard to remove by mechanical means and not damage, or destroy, the fossil. Limestone, siderite, fine grained sandstones and other natural material make up the fossils encasing matrix. If testing reveals that this matrix is too hard to be removed safely the acid reduction method should be considered. In the field the worker(s) should collect samples of the matrix which is free of fossils for the lab worker(s) to use as test material. If the matrix is limestone, for example, the lab worker(s) may choose a solution of sufficient strength as to dissolve the matrix yet not erode the fossil. Even then this method requires a very careful application of the acid divided by neutralization and drying periods where protective coatings can be applied to the fossil prior to repeating the acid bath.

The lab worker(s) should save the residue from the dissolved matrix for later examination should a study of the Palynology be undertaken.

theropod asked;
4. How does one determine if a shed theropod tooth was lost externally during feeding or has been swallowed while feeding and past through the digestive tract of the owner?

Of all these questions this is the most simple to answer. The teeth of all dinosaurs were shed on a regular basis, much like sharks. The teeth that were lost while feeding will remain, under normal conditions, very well preserved while the teeth that have been swallowed will have digestive juices acting to erode them. The digested teeth will have pitting and other scaring characteristics which can only come about as a result of exposure to the highly aggressive digestive juices. Most theropods of any size also consumed bone in the act of feeding and their digestive tract was evolved to deal with this to extract the nutrients contained therein. A tooth, while much harder than normal bone, will still suffer degrading erosion from exposure to the digestion process.