Extinction doesn't have to be forever, especially if you're a particularly resilient snail.

Believed to be extinct for more than 60 years, the Rhodacmea filosa, a freshwater mollusk, has been discovered at the Coosa River in Alabama's Mobile River Basin.

The basin was originally thought to be responsible for the species’ extinction.

The snails are fond of fast-moving rivers and streams where they graze on microscopic algae. When the river was dammed and locked throughout the 20th century, the flowing rivers went away, and it was believed that the mollusks went with them.

"Their habitat was destroyed in huge chunks," said Diarmaid Ó Foighil, professor of ecology and evolutionary biology and a curator at the University of Michigan’s Museum of Zoology and leader of the study.

Forty-seven of 139 endemic mollusk species were lost due to the basin's industrialization, representing one-third of all known freshwater mollusk extinctions worldwide.

Twenty years ago, scientists from the Alabama Aquatic Biodiversity Center (AABBC) decided to search areas around the basin that weren't affected by the damming to locate and hopefully save plant life that had survived. The scientists planned on nurturing the plants in a lab and then reintroducing them in compatible regions.

While searching for the fauna, the director of the AABBC, Paul Johnson, discovered the mollusks. To make sure that snails were in fact Rhodacmea filosa, Johnson consulted with the Museum of Zoology, which has an extensive collection of mollusks samples and records.

"This is very good news," Ó Foighil said. "With conservation biology, usually it's all gloom and doom, but this is one of those rare events where we have something positive to say."

Ó Foighil is optimistic that the mollusks can continue to survive.

"We have a persistent population in this little tributary, but we also now have in place the infrastructure for their captive breeding and reintroduction to other tributaries."

This study was published on May 31 in the open-access journal PLoS One. The study received funding from the State Wildlife Grant Program, the U.S. Fish and Wildlife Service and the National Science Foundation.