Travel complications prevented John’s and George’s weekly Friday native plant field trip, so we’ll take a side trip today. I’ve been in Pennsylvania for a taste of “Pennsylvanian Period” fossils roughly 300 million years old, my favorites being Seed Ferns. (Long-extinct seed plants with ferny leaves.)
But who needs Pennsylvania for fossils? Florida is paleontology paradise, although vastly more recent.
Most of our local fossils date to the Pleistocene Epoch, which ran approximately 2.6 million – 12,000 years ago spanning the spell between the first humans ever, to the first humans to visit the Sunshine State.
Although dinosaurs were extinct for over 60 million years when South Florida dried out, our state hosted equally awesome paleo-mammals, such as giant ground sloths, sabretooth cats, cypress-eating mastodons, and additional furry Flintstones giants.
Today’s seashell fossils are a little smaller. Native plant roots mingle with them. No native plants field trip is complete without fossils underfoot. A construction site is an instant museum, I find more pretty seashells in the eroded canal bank behind my house than beach combing at Sanibel.
Fossil shells can be exasperating to identify. Much like identifying yellow Asteraceae wildflowers, any fool can match a specimen to a photo in a handbook, but open another book and discover lookalikes, lots of lookalikes. Farewell confidence! But it is great fun to look and try, not to mention a taste of evolution in everyday living. The species encountered are a mix of those still with us, others still living but not nearby, and the extinct.
The expert on these matters is FAU Professor Edward Petuch, who has authored several relevant books, perhaps the most appropriate to our haunts being, “The Geology of the Everglades and Adjacent Areas” (2007) authored with Charles Roberts.
Web resources stand by to help with the exasperation. The UF Natural History Museum has an online gallery of fossil shell photos. Another useful site is the Neogene Atlas of Ancient Life Southeastern United States.
Good luck! No single reference “does it all.”
The Pleistocene Epoch was a time of sea level fluctuations as glaciers waxed and waned, with southern Florida a blue lagoon repeatedly, except for a ring of raised “islands,” including the “Palm Beach Archipelago.” Most of the surface area, including where we botanize, was fishy repeatedly, finally above “for good” about 74,000 years ago.
The repeated dousings, climate wobbles, landform changes, and disturbances across space and time make for a complex system of fossil formations and paleo-communities across South Florida. The shells in my canal bank probably date back over 74,000 years, and in other places can be far older. After all the many millennia some look like they came from a tourist trap, some even remain glossy and colorful.