Living Fossils

This past summer, I was in Florida with a group of students trying to reconstruct the paleoenvironment of the state. We had the opportunity to go to several quarries and do some intense sampling of the shell beds. Among the fossils collected were many species of molluscs—bivalves (clams, oysters, etc.) and gastropods (whelks, slipper-shells, and limpets). The only chance we had to see these extant organisms was in Miguel Bay, which was composed mainly of Mangrove Islands.

One of the most interesting experiences I’ve had in New Zealand has been the exploration of the rocky intertidal habitat. We travelled (pleasantly though unexpectedly) to Mt. Maunganui and had a chance to walk around the surrounding beach at low tide. Due to the last few days of inclement weather, the surf was higher than normal and definitely quite rough. We learned that the rocks we saw were volcanic, and some of them were rocks known as ignimbrite. The ignimbrite we saw had large phenocrysts of various colors—pink, green, blue, and purple—cemented together with a tan matrix. Waves and tides as well as the crystallization and dissolution of salt from sea water created pockets in the rocks, which provide protected habitats for a variety of creatures. We also learned about zonation and the environmental conditions necessary for certain species to live. This zonation was extremely evident in yesterday’s travels to Cathedral cove on the Coromandel peninsula. We were able to see the oysters that formed the lowest zone. Limpets, chitons (see picture), and barnacles made up the next zone atop the oysters. It was a privilege to see the limpets alive and thriving, since I had only seen fossilized ones up to this point. It gave me a new respect for taxonomists because limpets are challenging enough to identify when they are living let alone when they’ve been fossilized. The Florida fossils lacked coloration, and often all that was left were the apices. It has been most enjoyable to experience and compare these living creatures to their fossilize kin. Plus, you can’t beat the location!