Ninety miles from the sea, bone white against the muddy black banks of the Alabama River, the sand dollar stands out.

The distinctive, petal-like pattern on its surface is perfect and unmistakable, but its presence so far from the Gulf of Mexico is wholly unexpected. Gazing up river along the ledge, you see many more, thousands even. The sand dollars spill from the riverbank in clumps, some broken, some whole, some looking as if they just washed up out of the Gulf.

Those that have been exposed to the sun and the elements for a time have bleached white, but for the most part, the sand dollars are stained a delicate sepia.

A fitting color for ancient fossils.

A short way up river, another ledge is covered in giant, fossilized oysters. They are a different species than the oysters living along the coast today. This species, Cubitostrea sellaeformis, is known for the uniquely twisted shape of the shells.

“Oysters occur in many Coastal Plain formations,” said Andy Rindsberg, a paleontologist with the University of West Alabama specializing in fossils of aquatic creatures. “Some of the most spectacular -- Cubitostrea sellaeformis, shaped like saddles -- are from the middle Eocene Lisbon Formation at Claiborne.”

The middle Eocene era occurred around 35 million years ago. At the time, the saddle shaped oysters were common across the American south, from Louisiana to the Carolinas. Alabama is one of the best places to find the fossils. The oysters along the river are large, with some fossils weighing several pounds. Among paleontologists, the peculiar shape of the shell is a dead giveaway as to the species.

The presence of the oysters and sand dollars so far from the present day coastline has helped scientists understand the dramatic changes in sea level, dating back millions of years.

Forty million years ago, most of Florida, and much of Mississippi, Louisiana, Georgia and Texas were underwater, submerged under an ancient version of the Gulf of Mexico. With bluffs along the river south of the Claiborne Dam reaching up 200 feet, Rindsberg said fossils from many ancient eras can be found.

As early as the 1800s, the fossil formations along the Alabama River were gaining widespread notice. Cockles, sea biscuits and large conchs all poke from the mud and sand along the river’s banks.

“In taking up the study of the Coastal Plain of Alabama, attention was naturally turned to this part of it, the river banks holding out greatest promise,” reads a report from 1887 by E.A. Smith, State Geologist of Alabama. “How well this promise has been fulfilled may be seen in the following pages, which show that we have in this section of Alabama the most complete and varied series of Eocene and Cretaceous strata known in the United States.”

Sand dollar fossils 8 Gallery: Sand dollar fossils

Unfortunately, many of the fossil deposits Smith studied in the 1880s have since been lost, submerged beneath the vast lakes created by the damming of Alabama’s rivers. Other sites are now buried under office buildings. Some have simply been overgrown to vegetation and lost to time.

“There are several fossil sites in that area that are frequented by personal fossil collectors, museum collectors, and university collectors. There are fantastic sand dollars, a wide range of gastropods, and lots of shark teeth,” said Sandy Ebersole, with the Geological Survey of Alabama. “The preservation is spectacular, and the biodiversity is very high. It makes for a great area to collect.”

Ebersole said the quality of fossils depends on a host of factors, including how quickly the creatures were buried, how much clay was present when they were buried, and how much water they have been exposed to.

“If they were buried very quickly, as opposed to slowly, there will be a much higher degree of preservation,” Ebersole said. “If you have a major storm systems come through our coastal area now, we have a lot of rainfall that will move through, and then a lot of sediments come down the rivers. Organisms living on the seafloor, like oysters and sand dollars, they are stuck there and get buried. ”

The same was true millions of years ago, she said.

Lyman Toulmin conducted the most exhaustive research on Alabama’s fossil relics in 1977. His book serves as a bible for paleontologists studying the area.

“Southwestern Alabama, especially, is famous for abundance of of unweathered outcrops of fossiliferous marine beds,” Toulmin wrote. “The past is the key to the present. The kinds of living organisms and their distribution in various environments in the Gulf today are a product of migration, adaptation, evolution, and extinction of organisms that lived in the Gulf Coast area in the geologic past. Past and present Gulf of Mexico faunas are intimately related.”