Calcite crystals – (KAL-sight) While calcite is one of the most common minerals in Florida, it’s rarely found in crystal form. Here, calcite in groundwater filled the empty spaces in and around fossilized clams, sea snails, and coral and crystallized, similar to how geodes form.
Dermal denticle – (DURR-muhl DEN-tickle) Also known as placoid scales, denticles are essentially modified teeth (not actual scales) that cover the skin of sharks, rays, and skates. They not only act as armor, affording protection from predators and parasites alike, but also increase the animal’s hydrodynamics by reducing drag and turbulence as it swims.
Dugong – (DOO-gong) A close relative of the manatee, it once roamed Florida waters in huge numbers but is now found exclusively in the eastern hemisphere – the east coast of Africa, western India, southeast Asia, and northern Australia. The most striking physical difference between the two is their tails. Whereas manatees have fan-like tails, those of dugongs are “fluked,” or v-shaped, like a dolphin’s. Dugongs are also exclusively marine (meaning they never leave saltwater), whereas manatees are both fresh and saltwater tolerant.
Glyptodont – (GLIPT-oh-dont) A giant, extinct armadillo relative that grew to the size of a VW Beetle: 5’ tall, 11’ long, and over 4,000 lbs. Its head, shell (or carapace), and tail were heavily armored by over a thousand individual scutes that were up to an inch thick, with an appearance somewhat resembling the unrelated and much older Ankylosaurid dinosaurs in a case of what paleontologists call convergent evolution, in which ecological pressures lead two or more independent species to evolve similar traits, features, or characteristics.
Megalodon – (MEGA-luh-don) The largest shark to ever live, it grew to lengths of over 60′ with teeth up to 7.5″ long. These enormous teeth, coupled with the strongest bite force in animal history (40,000 psi), allowed it to feed on large marine mammals like dolphins, dugongs, seals, walruses, and even whales in addition to sea turtles, large fish, and other sharks.
Mouth plates – Flattened plates inside the mouths of certain fish or rays that are used to crush their armored prey, such as crabs, clams, sea snails, shrimp, urchins, etc.
Mya – Abbreviation for “million years ago.”
Osteoderm – (AHS-tee-oh-derm) Latin for bone (osteo-) and skin (derm-), osteoderms are just that: bony deposits in the skin. In alligators and crocodiles, they serve three main functions: as armor; as a thermoregulatory apparatus (that is, they can either transfer warmth from the sun directly to the blood or dissipate heat if the animal becomes too warm); and to prevent acidosis, a condition in which acidic carbon dioxide builds up in the blood of a submerged, breath-holding animal, by releasing alkaline calcium and magnesium ions into the bloodstream.
Scute – (skyoot) Though often used interchangeably with the term osteoderm, scutes are technically the keratinous (the same material your hair and fingernails are made from) sheaths that lie on top of the osteoderm. Neural (NURR-uhl) scutes, or elements, are the scutes that run down the center of a turtle’s back and which fuse to the spine.
Steinkern – (SHTINE-kern) German for stone (stein) and kernel (kern), steinkerns are the internal molds, or stone casings, of bivalves (hinge-shelled mollusks like clams or oysters) and gastropods (spiral-shelled mollusks like snails or whelks).
Vertebrae (pl); vertebra (sg) – (VERT-uh-bray (pl); VERT-uh-bruh (sg) An animal’s spine or backbone(s). While taking on many different shapes and sizes depending on the animal and location in the spinal column, their function remains the same: to protect the spinal cord while providing flexibility.
So just what is a fossil, anyway?
Fossils are the preserved remains – or traces of remains, in the case of nests, burrows, dung (coprolite), or footprints – of once living organisms. There are several types of fossils, but here we’ll focus on the most common: permineralized. For this kind of fossilization to occur, an organism needs to be buried in sediment soon after its demise. Either the plant or animal has to die in (or close to) a body of water or its remains have to be transported there, by floods or scavengers. Once buried, it must remain undisturbed for millenia (though the time it takes to fully fossilize varies, it’s typically at least 10,000 years). Slowly, minerals in the water and sediment begin to seep into the porous areas of plants or the bones, teeth, and occasionally even soft tissues of animals, depositing a mineral matrix where cells once existed. A fossil is, in essence, a mineral copy of the original organism.
Why are there so many fossils in Florida?
Florida inherited an immense quantity of mineral-rich sands and clays from the erosion of the Appalachian Mountains, is surrounded by shallow seas and intersected by extensive river systems, has had very little geological volatility (things like earthquakes or volcanic eruptions, which could disturb the fossilization process), and served as an ideal habitat for a wide variety of ancient plant and animal species. These conditions, spanning tens of millions of years, led to Florida having some of the richest and most varied Cenozoic era fossil deposits in the world. It’s worth noting, however, that fossilization was and still is an incredibly rare occurrence, and that the vast majority of organisms to have ever lived have been lost to the [almost] unstoppable biological forces of nature. Every fossil is the result of a series of highly unlikely events, and that’s part of what makes them so special.
How old are these fossils?
Florida began its rise out of the sea during the Oligocene epoch, as a landmass called Orange Island, 30 some odd mya. So while you won’t find any dinosaur fossils here (we missed them by around 30 million years), you’ll find an abundance of mammal, bird, fish, reptile, amphibian, and invertebrate material, predominantly dating from the Miocene onward through the Pliocene and Pleistocene and into our modern epoch, the Holocene (~23 million to 10,000 years old), with some rare finds dating as far back as the Eocene, over 50 mya.
Why do you sometimes find marine fossils on land and terrestrial fossils at sea?
Florida, being so low in elevation, is uniquely prone to the effects of shifts in global climate. During cooler (glacial) periods, much of the earth’s water gets locked up in vast ice sheets and glaciers, which results in drastic drops in sea level (called sea level lowstands). Inversely, during warmer (interglacial) periods, all that ice melts and sea levels rise (sea level highstands). These swings can be several hundred feet, and during extremes (glacial maxima and minima, respectively), Florida has been over twice as wide as it is today (as recently as ~18,000 years ago) or almost completely inundated by water (during multiple stretches of the Miocene, 23 to 5.3 mya). This means that 13 foot tall mammoths once grazed where there is now over 400 feet of water and megalodon sharks bigger than school buses terrorized seas that once covered almost the entire state.
Why do you find older fossils mixed in with younger ones?
In geology, there is something called “the law of superposition.” It states that each rock or sediment layer (strata) is younger than the one it sits on top of. Older rock must form first, then younger rock forms on top of that, and so on. Fossils are the same way. The older a fossil is, the deeper it should be in relation to younger fossils. But in Florida it’s not uncommon to find 20 million year old shark teeth in the same layer as 20,000 year old horse bones, for example. Why is that? Well, when sea levels fall extensive river systems often form, eroding through layers of long undisturbed strata and exposing, transporting, and consolidating previously formed fossils, potentially from many different time periods. As sea levels once again rise, or river systems inevitably change course, these fossils, now all jumbled together, become reburied in sediment, occasionally with recently deceased friends in tow who are just starting their fossil journeys. As Florida is on the front line for changes in sea level, this scenario has played out countless times throughout its history. The resulting mish mash of fossils can be frustrating for paleontologists who have to try to work their way back through history but exhilarating for us hobbyists!
How do you find all this stuff?
Perhaps the easiest and most accessible way to find fossils in Florida is to buy a scoop and sifter and head to the Venice area beaches, where a fossil-rich deposit called the Peace River Formation is exposed just offshore. Fossils, especially shark teeth, are constantly eroded out of this layer and washed ashore through tidal action, currents, and storms. Sometimes you don’t even need to sift, they’ll be washed right up on the shoreline! Digging and sifting in the creeks and rivers that crisscross the state is another fantastic option (pro-tip: look for areas with lots of gravel). If you’re comfortable underwater, snorkeling or SCUBA/hookah diving is my favorite way to hunt, either off the Venice coast or in creeks and rivers (just watch out for sharks, gators, and snakes!). Last but not least are land sites. As construction or mining crews dig, they occasionally expose rich fossil deposits. Some of the best finds in the state have been in phosphate mines, where numerous fully articulated skeletons have been found. As tempting as it can be to go waltzing through an active construction site, however, be forewarned that trespassing on a construction site or mine is a potential felony! Best to seek permission first or find a site that is open to the public. No fossil is worth landing in jail.
*A fossil hunting permit is required if you plan on collecting anything other than fossilized shark teeth or invertebrates (shells, echinoids, etc) on public land in Florida. They’re only $5 per year and available to residents and visitors alike. I highly recommend obtaining one if you plan on doing any fossil hunting in the state. Google “Florida fossil permit” to learn how.
What other kinds of animals lived in Florida?
Ground-dwelling sloths up to 20’ long; 7’ tall carnivorous “terror birds;” 30’ long crocodiles; 5’ tall beavers; 6’ long tortoises; mammoths, mastodons, gomphotheres, and other, even more bizarre, shovel-tusked elephant relatives; short faced bears; dire wolves; saber toothed cats; giant armadillos and their relatives, the glyptodonts, the latter of which grew to the size of a VW Beetle; basilosauruses; jaguars; American lions; hornless rhinos; miniature three-toed horses and a multitude of other proto-horses; walruses; seals; tapirs; capybara; bison; humpless, long-necked “giraffe” camels; llamas; and much, much more.
Latin names: Holmesina floridanus; Holmesina septentrionalis
Though commonly called giant armadillos, these animals were actually pampatheres, an extinct line of armadillo-like creatures. Originally evolving in South America, they dispersed northward after the Isthmus of Panama was formed roughly 2.7 mya in an event known as the Great American Biotic Interchange, in which tremendous migrations of plant and animal species took place between the Americas via this newly formed land bridge. Unlike modern armadillos, which are insectivorous or omnivorous, giant armadillos were strictly herbivorous. They were much larger than the giant armadillos of today (found in South America), with the larger of the two species (septentrionalis) growing to 3’ tall, 6.5’ long, and weighing 600 lbs. Their shells were covered by hundreds of individual scutes of many shapes, sizes, and functions, with some even overlapping one another (called imbricating scutes), forming bands similar to those of modern armadillos. These bands afforded flexibility while still offering protection from predators.
Latin name: Glyptotherium floridanum
Glyptodonts are an extinct relative of armadillos, anteaters, and sloths that similarly evolved in South America before migrating northward. They dwarfed their giant armadillo cousins, growing to 5’ tall, 11’ long, and weighing over 4,000 lbs: about the size of a VW Beetle. Their heavily armored heads, tails, and dome-shaped shells were equipped with over a thousand individual scutes, and they bore a slight resemblance to the unrelated and much older Ankylosaurid dinosaurs in a case of what paleontologists call convergent evolution, in which ecological pressures lead two or more different species to evolve similar traits, features, or characteristics.
Latin name: Equus ferus
The evolutionary lineage of horses is perhaps the best attested in all of paleontology, starting in North America 50+ mya with a 20” tall hoofed mammal called Eohippus. Unlike modern horses, which are grazers (grass-eaters) and have one, unpadded, hoof per leg, this diminutive ancestor was a browser (meaning it ate leaves, soft shoots, and/or shrubs) and had four padded front hooves per leg with three in the rear. Over the course of horse evolution, which is a complex web that illustrates how diverse evolutionary mechanisms can truly be, the following trends ultimately won out: increase in overall size; reduction in number of hooves and loss of footpads; lengthening of legs and a fusion of the lower leg bones; increase in head and brain size; and a transition to crested, high-crowned teeth ideal for grazing (called hypsodont dentition). When a horse eats, it inadvertently yanks up grit and soil in addition to grass. Grass requires a lot of hard, grinding chewing to make it digestible. The inclusion of this grit causes teeth to literally wear away over time. (Though it was once believed that microscopic, abrasive granules in grass called phytoliths were primarily responsible for the tooth erosion experienced by many grazers, recent studies indicate that grit is the main culprit). As a result, horse teeth evolved to slowly erupt out of the gum line as they’re worn away. Each tooth tells a story: a long tooth (they start at ~5”) indicates that the horse it belonged to died at a young age, while a worn tooth, sometimes hardly more than just the roots, relays that its owner lived a long life.
Latin name: Otodus megalodon
The megalodon is the largest shark that ever existed. It’s estimated to have grown to over 60’ long and weigh 60+ tons, with jaws ~10’ wide and teeth over 7” long, with the largest tooth on record measuring 7.48” from tip to corner (which is how shark teeth are measured). It first appears in the fossil record around 20 mya before disappearing ~3.5 mya. While scientists once believed that the megalodon was an ancestor of the modern great white, recent evidence points to them evolving from different lineages and the two species not being closely related at all. With the strongest bite force of any animal in history at over 40,000 lbs/sq inch, it feasted on large marine mammals like dolphins, dugongs, manatees, sea lions, seals, and even whales, in addition to sea turtles, large fish, and other sharks. It’s thought to have primarily hunted in warm, shallow seas across the globe, as evidenced by its fossilized teeth being found from Australia to Indonesia, Morocco, Peru, Florida, and beyond.
Taxonomic clade: Selachimorpha
Sharks are a group of cartilaginous (car-tuh-LADGE-in-iss) fish (those with skeletons made of cartilage rather than bone) that evolved during the Jurassic period some 200 mya, though their direct lineage goes back to at least the Silurian period, roughly 440 mya. This predates the formation of TREES by around 80 million years. Shark teeth are embedded in the gums rather than the jaw, and are constantly lost and replaced throughout a shark’s life. Some sharks go through as many as 35,000 teeth in a lifetime. The size and shape of each species’ teeth can tell you about their diet: long, needle-like teeth are ideal for gripping slippery fish and squid; large, triangular, serrated teeth for slicing through larger fish and marine mammals; and broad, flat teeth to crush crustaceans and mollusks. You can find numerous species of fossilized shark teeth in Florida, including (but not limited to) – in roughly increasing order of rarity – lemon; bull/dusky (genus Carcharhinus – the teeth represented by this broad genus can be difficult to tell apart); hammerhead; sand tiger; hemipristis (or snaggletooth); tiger; lesser white or hastalis (also commonly called “mako”); megalodon; great white; cow; giant thresher; and benedini.
Taxonomic infraorder: Cetacea
Cetaceans (seh-TAY-shenz) are a group of mammals that initially evolved on land before “re-entering” the water 50 some odd mya. Their immediate ancestors were amphibious and bred on land (similar to seals) and their closest modern relative is the hippopotamus. There are two modern groups of Cetaceans: the toothed whales, or Odontocetes (oh-DON-tuh-seats), which include orcas, sperm whales, dolphins, and porpoises and which use high pitched clicks and pops to echolocate and communicate; and baleen whales, or Mysticetes (MISS-tuh-seats), which include blue and humpback whales and which hear and communicate at much lower frequencies that can be heard by other whales hundreds of miles away. As whales transitioned from amphibious to purely aquatic, their ears had to adapt as well: from an early compromise of hearing just ok both above and below water, to the hyper-specialized, underwater eyes that they function as today. Few other animals are as reliant on hearing as whales.