Winding through South Carolina's low country, the Cooper River is a reed-lined haven for sportfish and shorebirds. The waterway originates from Lake Moultrie in Berkeley County. From there it goes all the way to Charleston, where it joins the Ashley and the Wando to form that city's world-famous harbor. (Ever heard of Fort Sumter?)
The Cooper River takes its name from Anthony Ashley Cooper, a 17th century English gentleman. As time passed, it became a lifeline in the region's burgeoning rice trade. But the Cooper also bears the hallmarks of a much older chapter in South Carolina history.
If you know where to look and you have scuba gear at hand, you might just be able to find a giant tusk lurking beneath the surface of the water.
Matthew Weas knows that feeling. He and his father, Joe Harvey, are experienced local divers who patrol the Cooper in search of fossils - many of which are on display at the Berkeley County Museum in Moncks Corner, South Carolina.
Not all the giants they encounter are prehistoric. To hear Weas tell it, he comes into contact with living modern river beasts are not uncommon. "I had one [catfish] swallow my hand in a tree trunk underwater, a manatee breaks the surface as I swam back to the boat... [and] alligators are swimming towards me," he says via email. Once he came "nose-to-nose" with an alligator about 10 feet long.
Cave of Wonders
The American alligator may be synonymous with the South, but underwater fossil hunting is a global pastime. Outside the US, divers have encountered paleo-treasures in places like Australia, Bali, Brazil, Indonesia, Mexico and the Bahamas.
In 2014, a bona fide 'lemur graveyard' was discovered in the submerged caves of Madagascar's Tsimanampetsotsa National Park. The major find was made possible by an international collaboration between anthropologists, paleontologists and divers.
Hundreds of bones appeared in the underwater sediments. Some came from modern-day species such as the invasive black rat. Other remains were left by animals that became extinct over the past millennia.
The site quickly established itself as the world's largest cache of Pachylemur fossils. This creature, an ancient relative of the ruffed lemur, was about twice as heavy, weighing an estimated 10 kilos. It would be completely dwarfed by the size of a gorilla Mesopropithecus a giant lemur that is also represented in these caves.
The diving team also recovered material from pygmy hippos, elephant birds and horned crocodiles, along with the rare, nearly complete skull of another extinct lemur species.
Gaining access to the premium was not easy. The caves in question were probably once dry, but today they are part of a flooded sinkhole. Currently, the system's most fossil-laden cave is 80 feet deep. It is a dark environment with a complex layout, full of horizontal corridors and murky water.
In short, this is not a place for novice divers. Cave diving is generally a high-risk sport; if you wander off course, you can't always rise straight to the surface. To avoid getting lost, the dive specialists from that 2014 team followed their route with approximately 268 meters of safety lines.
Preparation is key
Another costly sinkhole is the Page-Ladson site in northwest Florida. Hidden beneath the Aucilla River, it has yielded some of the oldest known human artifacts in North America. Equally fascinating are the site's mastodon bones, including some 14,550-year-old fossils with scars that indicate the animals were slaughtered by ancient Floridians.
Here tannins are really bothersome. Tannins, an essential component of leather, are chemical compounds released by various plants. When these seep into ponds or rivers, they can turn the water black-brown. It goes without saying that this damages visibility. In some corners of the Aucilla, the tannins help block sunlight, plunging anything deeper than 10 feet below the surface into inky darkness.
To the north in the Cooper River, divers face the same problem. To see clearly, they - and their colleagues from Aucilla - make good use of high-wattage underwater lamps.
Weas says he and his father wear Dive-Rite "cave lights" on their helmets. The rest of the duo's equipment would look quite familiar to other recreational divers. "We use the stock tank, regulators and BCDs," says Weas. (For the record, BCD stands for "Buoyancy Compensating Device," a wearable gadget used to keep divers at the desired depth.)
During summer dives, Weas and Harvey can comfortably put on pants and a T-shirt. But in certain weather conditions, dry suits, semi-dry suits or wetsuits may be more suitable. Because the Cooper receives strong tidal currents, the speed of the water at any time affects their schedule. Faster currents make for shorter excursions.
Basking Sharks... And Beavers?!
Why do people have to go through all these problems when there are tons of fossils on dry land? For starters, immersion in water has some conservation benefits. Deep in the bowels of a sunken cave, bones are less likely to be disturbed - by scavengers or the ravages of an open-air climate.
And while terrestrial fossils are often encrusted in rock, some bones are washed clean by the current in flowing rivers.
Most of the material Weas discovers in the Cooper River comes from two different points in geologic time. The river's most sought-after fossils are likely shark teeth from the Miocene period, which lasted 23 million to 5.3 million years ago. Some of these chompers grow quite large: a tooth from the extinct megalodon shark can be up to 19.3 centimeters long!
"Shark teeth are the most common finds," says Weas, "although whale ear bones are also found [in] a close second."
Other Cooper River fossils were deposited during the more recent Pleistocene. That started just 2.6 million years ago and ended just 11,700 years before the present. At the time, sea levels were lower and the Carolina coastline was further east.
Over the years, Weas and Harvey have freed the bones of Pleistocene mammoths, capybaras, ungulate herbivores, and giant beavers. The latter requires an explanation. During the last ice age, North American wetlands were occupied by Castoroides 2.5 meter long beavers that probably weighed 100 kilos or more.
It's undoubtedly scary when a manatee sneaks up on you. But imagine taking a dip with one of those mega rodents! Thanks, but no thanks.
That is interestingBritain was connected to the rest of mainland Europe only 8,200 years ago. For this reason, mammoth bones are periodically dredged from the North Sea, which separates Britain from its continental neighbors.
Original article: River-bottom Bones: The Strange World of Underwater Fossil Hunting
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