Laboratory work consists essentially in the preparation of fossils (i.e., getting them ready for anatomical studies). Preparation is a step in vertebrate paleontology, which follows the field excavation. Preparation is the process by which the sediment that surrounds the fossils is removed, thus exposing its anatomical details.
The PaleoMoz team working together in the fossil preparation laboratory.
Mechanical preparation
Opening of the sample and Photograph: opening of the specimen was done carefully so as not to miss any fragment; photographic records were made in several observation views to monitor the progress of the preparation during the subsequent works.
Preliminary specimen cleaning: consists of washing the specimen under running water with a brush. The fossil sample is left drying at room temperature. It may vary depending on the air temperature and humidity, but it does not exceed 2 hours.
Consolidation: Firstly, a detailed verification of the specimen to distinguish the bone and the matrix allows a correct application of the consolidant. Using abrush in the fragile zones of the specimen, the consolidant (e.g., Paraloid) is applied on the bone. This reinforces the specimen so that during the use of the grinding wheel and airscribe the bone parts do not break.
Before proceeding to the removal of the matrix it was necessary to look again at the sample and establish the first sites for matrix removal.
Marisa Amaral is consolidating a fossil vertebrate sample with Paraloid.
Matrix Removal (sediment): it consists in the use of the pneumatic micro-hammer (airscribe). We start from the bulkier parts of the matrix and always the area furthest from the bone to the nearest area.
On the other hand, not all samples need the angle grinder to be used. It depends on the matrix volume. There are cases where the amount of the matrix is so small that it is not necessary to use the angle grinder.
Mechanical preparation using an airscribe.
Chemical Preparation
Acid bath: after removal of the largest possible volume of matrix around the specimen, we use formic acid (at 5%), diluted in running water. We add a spoonful of calcium phosphate powder, preventing the acid from dissolving the fossil bone as well. The specimen exposure time to the acid bath depends on the amount of the matrix in the sample.
Washing and immersion in a new acid bath: after the acid bath, the specimen is immersed in running water for the same amount of time as the acid bath. This reduces the acid concentration, thus neutralizing the acid effect.
Again, the acid bath is repeated and alternated with the water bath, in order to have only the bone exposed. This procedure is repeated successively until all the anatomical details of interest for the later study are available for examination.
Text by: Ivânia Loide
Editing by: Ricardo Araújo