The Shells Beneath our Hiking Boots

15 Aug
The perfect condition of fossils never ceases to amaze and inform.

The perfect condition of fossils never ceases to amaze and inform.

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.)

Seed Fern leaflet from deep in a PA ravine. 200 million years old?

Seed Fern leaflet from deep in a PA ravine. 300 million years old?

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.

Mastodon lower jaw. Any DNA left there?

Mastodon lower jaw. Any DNA left there?

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.

Off the beach this week, or dug up after 74,000 plus years??

Off the beach this week, or dug up after 74,000 plus years??

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.

No, I'm not providing identifications, no confidence in my own work (although this is an

No, I’m not providing identifications, no confidence in my own work (although this is an “easy” one).

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.

Chione shells are the vast majority around my house.

Chione shells are the vast majority around my house.

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.

Fresh and new after a few eons

Fresh and new after a few eons


Posted by on August 15, 2015 in Uncategorized


9 responses to “The Shells Beneath our Hiking Boots

  1. Felicity Rask

    August 15, 2015 at 6:29 pm

    By coincidence we spent this morning birdwatching around Craney Island Dredged Material Management Area in Portsmouth VA. This island extension has for the last 60+ years been increasing in size with dredge spoil from the Elizabeth and James Rivers. The perimeter roads are a veritable treasure trove of fossils but I was not paying attention. I was watching birds, unaware of what we carelessly scrunched across … Felicity Rask Gloucester, VA


    • George Rogers

      August 15, 2015 at 6:40 pm

      Hi Felicity…that sounds like Fun! Something that has always bothered me living a botanical life is so often under-appreciating to the bigger context, the birds, amphibians, reptiles, mammals, arthropods, starry skies, and things we scrunch across. Bet there are some shark teeth in those dredgings. What birds did you see?

      • FelicityRask

        August 16, 2015 at 10:33 am

        Better a Master of one than a Jack of all!
        Easier to tell which birds I didn’t see but others did: Northern Shoveller (a favourite of mine), Least Bittern and a Ruddy Duck in full breeding colors. All common enough in FL and VA in the winter months but unusual at this time of year and in their current plumage. I also saw lots of Black Necked Stilts in their beautiful tuxedos and elegant gigolo boots and Snowy Egrets in their flashy yellow street corner shoes! I spotted a Sora but it skulked away before I could get anyone to confirm.
        I have found 14 Monarch Caterpillars on A. Incarnate but no A. Syriaca on which to feed them. It is all gone from the ditches, roadsides and gardens where it used to be so common. Eradicated. This may be a worse disaster than the invasive exotics and this one deliberate. I find that some people don’t agree with raising Monarchs though I haven’t quite figured out why.
        Oh for a quiet fireside chat, poolside might be better, with Darwin who might have an interesting take on all these matters … fun to be off topic for a short while!

      • George Rogers

        August 16, 2015 at 1:37 pm

        Felicity, Nice day of birding! And the stilts all dressed up. Weirdly, had a least bittern visit my back yard canal about a week ago and stay around a few hours, a special treat.

  2. theshrubqueen

    August 15, 2015 at 8:09 pm

    Hey George, I find more weird shells every time my new greyhound tears up more, um native plant material. He also finds plants.

  3. George Rogers

    August 15, 2015 at 9:15 pm

    Amelia, What a good dog, helping you enjoy the evolution.

  4. Suellen Granberry-Hager

    August 16, 2015 at 9:06 pm

    I had the pleasure of being in two of Dr. Petuch’s classes at FAU (Physical Geology and Coastal and Marine Science). We took a field trip to Ruck’s Pit, and I found some re-calcified clam shells with beautiful golden dogtooth calcite inside. I never worry too much about identifying shells. I just enjoy them (“Oooh, pink and pretty”).

  5. Katie MacMillen

    August 21, 2015 at 9:38 am

    Love the branching out into a little non-plant-y topic! Kids at our summer camp and visitors to our nature center can happily sit and pore over the pathway and parking lot fossils. Yet another thing in Florida that amazes me – so many fossils so densely packed that they get used as permeable surface!

    Katie Mac Millen, Biological Technician
    Pasco County Natural Resources
    4111 Land O’ Lakes Blvd.
    Land O’ Lakes FL 34639
    Phone: 727.847.2411 x 8333

    • George Rogers

      August 21, 2015 at 1:36 pm

      Hi Katie, isn’t funny how we have to send students to Costa Rica to study ecology when there’s enough to learn literally in a parking lot to fill a year.


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