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Swell shells


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If you pull a fan-shaped shell from a stream in southeastern Virginia this summer — especially if that stream lies east of Interstate 95 — pay attention.

You may have found the trace of an ocean ecosystem that covered the Virginia coastal plain 4.5 million years ago.

Officially known as the Chesapecten jeffersonius, this scallop shell became the state fossil of Virginia in 1993. Lauck Ward, curator emeritus at the Virginia Museum of Natural History, helped to name it.

“It’s a scallop of pretty spectacular proportions, 7–11 inches across,” Ward said. “They’re huge suckers.”

The Chesapecten has a rounded shape, usually with nine to 12 raised ribs that join in a point at the base. It was a common scallop in an ancient age, floating through the water while the Appalachian Mountains were forming, mastodons thrived and three-toed horses were about to go extinct.

The Chesapecten was the first fossil described in North America by European explorers, in 1687. In 1824, it was named the Pectin jeffersonius in honor of Thomas Jefferson. “In Latin, pectin means comb,” Ward said. “And for a while, every scallop ended up under Pectin.”

Ward helped to rename this specific fossil to reflect its Chesapeake connection and worked with colleagues to win the state designation. Today, the Chesapecten can still be found in stream valleys and river beaches in southeastern Virginia and eastern North Carolina. According to Ward, amateur fossil hunters stand a good chance of finding it. “From the Rappahannock River south, you can collect them in almost every river you cross,” he said.

Maryland has a state fossil too, also tied to its oceanic past, but finding one is a real prize.

It’s a type of Ecphora, the fossil of a marine snail much older than the Chesapecten. This particular Ecphora was common in ocean waters that covered southern Maryland and the Eastern Shore about 10 million years ago, when the world’s waters contained super-predators like megatooth sharks and giant crocodiles.

Maryland first named it the state fossil in 1984, but had to make the designation again in 1994 when it was given the longer and more scientifically accurate name of Ecphora gardnerae gardnerae Wilson.

Stephen Godfrey of the Calvert Marine Museum has studied countless fossils from the riverside cliffs of southern Maryland but still has a fondness for the Ecphora gardnerae. “It has these robust ribs that are very chunky, that give it a beautiful look and make it very strong,” Godfrey said. “They coil around the shell like an old barber shop sign or a helix.”

The other unique thing about the Maryland state fossil is its color. The vast majority are dark red or almost brown.

“It’s very unusual to find a fossil shell that has color associated with it,” Godfrey said. “The molecules that make up color in animals aren’t typically stable over time, so the pigments decompose and bright colors are lost. Generally, the older the fossil is, the less likely that its color is preserved. But for some reason, these Ecphora seem to preserve their original color.”

Ecphora gardnerae was also one of the first fossils from North America to be described and illustrated.

This specific Ecphora has mostly been found at sites along the St. Mary’s River that are closed to the public. But its cousins can sometimes be found on public land along Calvert Cliffs and other cliff exposures on the Patuxent and Potomac Rivers, where sediment was laid down about 18 million to 8 million years ago. Fossil hunters should proceed with caution because the cliffs are unstable and dangerous.

“The big ones are usually fist size but I’ve seen them as large as grapefruit,” Godfrey said. “And the tiny guys — I just got one yesterday. About the size of a kidney bean with little ribs. It was just so cute.”

State Fossils of the Chesapeake

District of Columbia: The Capitalsaurus is a dinosaur that lived about 110 million years ago and is thought to have walked on two legs like a Tyrannosaurus rex.

Delaware: The Belemnite, similar to today’s squid, was abundant 200 million to 66 million years ago. It had 10 arms and a siphon that pushed out water, which moved the animal backward.

Maryland: The Ecphora gardnerae was a large, meat-eating sea snail that lived in tidal waters. It went extinct 5 million years ago.

New York: The Eurypterus remipes was a sea scorpion that lived 432 million to 418 million years ago at the bottom of a shallow brackish sea. It was 5–8 inches long, with spiny appendages and a pair of swimming paddles.

Virginia: The Chesapecten jeffersonius, a scallop that lived 4 million to 5 million years ago on a coastal plain, is now most often found in stream valleys and on river beaches.

Pennsylvania: The trilobite Phacops rana lived between 405 million and 365 million years ago. It had exceptionally large, round eyes on the top of its head that gave the creature an almost 360-degree field of view.

West Virginia: The Megalonyx jeffersonii is a ground sloth that lived 10.3 million to 11,000 years ago and grew up to 10 feet long. It walked on all fours, but stood on its back two feet to rip down vegetation with its front claws.

Article originally published on the Bay Journal website on July 14, 2014.