University of Bristol EARTH SCIENCES

This paper investigates the remarkable preservation of exoskeleton remains that are found at the Rancho La Brea and McKittrick sites, by determining the decay resistance of the cuticles from fossilised beetles and crickets found at the sites.

The analysis was carried out using the above fossilised material and also the fresh and decayed cuticles of modern beetles and crickets, in order to compare like with like (same state of decay in fossils for the same state of decay in the modern specimens).

Using the Py-GC/MS technique it was established that altered proteins survived within the modern specimens following decay, but that these were heavily altered, the amazing find from this experiment was that this was the first time proteins had been generated within a fossilised specimen.

The findings indicate that chitin is the key to the abundance of arthropod cuticles preserved in organic form, rather than mineralised, in the fossil record, at the Rancho La Brea and McKittrick sites, as the asphalt medium appears to have promoted the preservation of chitin and thus enable the heavily altered protein molecules to be preserved.

Further study by Briggs et al(1998) discovered that the oldest fossil arthropods in which chitin is still surviving are 25 million years old. Older than this they are heavily altered and the chitin is unrecognisable.