Bone By Bone: The Delicate Art of Fossil Preparation

Friday, July 23 4:20 pm

Fossil preparation requires an uncommon degree of adaptability and patience. (c) AMNH/D. Finnin

Two decades ago, a chunk of sand containing a nearly perfect 80-million-year-old lizard fossil — just pulled loose from the red desert floor and resting on the hood of a Jeep — exploded into dust when touched by a member of the Museum’s annual summer expedition to the Gobi desert. A preparator knows why: paleontology depends on glue.

“Some of the fossils from Ukhaa Tolgod, this massive dinosaur graveyard found in 1993, survive only because they are so tightly packed in sand,” says Amy Davidson, one of the Museum’s senior fossil preparators, who happened to be on that expedition. In a cavernous room perched over several stories of meticulously labeled fossils, she darts to a beautifully fragile and nearly complete dinosaur skull.

“This fossil was also turning into crumbs,” she continues. “We need to know our adhesives. I stabilized the porous bone and sandy matrix (any material in which fossils are embedded) with just the right strength and solubility to be able to sculpt out the fossil, just like a magician pulls a tablecloth from under the table setting.” Last year, this delicate carnivorous cousin toTyrannosaurus rex was described and named Alioramus altai.

Fossil preparation requires an uncommon degree of adaptability and patience. Museum preparators bring to the task diverse sets of skills from such backgrounds as art, paleontology, and archaeology. They generally learn their craft on the job, drawing from related fields such as object conservation to adapt modern glues, solvents, and other archival materials to stabilize fragile areas or repair damage.
But the basic approach remains the same. Davidson, for example, removes her frameless glasses to face a fossil through her microscope, resting her wrists on a black velvet sandbag, securing a fine needle between her thumb and index finger, and using her third and fourth fingers to lightly touch the specimen. She moves almost imperceptibly, for minutes on end, carefully excavating a jaw from the soft sand. At the ready, laid out on a cutting board, are her preferred tools of the trade: brushes and droppers for dispensing glue, needles of different sizes and shapes for excavating, an air pedal for removing scraps of matrix, and glass jars of carefully labeled adhesives. Read more »