Digging Into The Deep Past

Press release from Emory University:

The discovery of the first known fossil iguana nesting burrow, on an outer island of the Bahamas, fills in a gap of scientific knowledge for a prehistoric behavior of an iconic lizard. PLOS ONE published the finding by scientists from Emory University, which also uncovers new clues to the geologic and natural history of the Bahamas.

Illustration shows a cross section of the prehistoric iguana burrow, and how the surrounding landscape may have looked during the Late Pleistocene Epoch. (Art by Anthony Martin)

Illustration shows a cross section of the prehistoric iguana burrow, and how the surrounding landscape may have looked during the Late Pleistocene Epoch. (Art by Anthony Martin)

The fossilized burrow dates back to the Late Pleistocene Epoch, about 115,000 years ago, and is located on the island of San Salvador — best known as the likely spot where Christopher Columbus made his first landfall in his 1492 voyage.

“San Salvador is one of the outer-most islands in the Bahamas chain and really isolated,” says Anthony Martin, a professor in Emory’s Department of Environmental Sciences and senior author of the PLOS ONE paper. “It’s a mystery how and when the modern-day San Salvadoran rock iguanas arrived there. Today, they are among the rarest lizards in the world, with only a few hundred of them left.”

Martin’s specialty is ichnology — the study of traces of life, such as tracks, nests and burrows. He documents modern-day traces to help him identify trace fossils from the deep past to learn about prehistoric animal behaviors.

Emory students explore a rocky shoreline of San Salvador during a 2015 field trip to the island. (Photo by Anthony Martin)

Emory students explore a rocky shoreline of San Salvador during a 2015 field trip to the island. (Photo by Anthony Martin)

The current discovery was made during a class field trip to San Salvador as part of the course “Modern and Ancient Tropical Environments,” co-taught by Martin and Melissa Hage, an assistant professor of environmental science at Emory’s Oxford College and a co-author of the paper. Co-authors also include two former undergraduates from the class: Dottie Stearns (now in medical school at the University of Colorado) and Meredith Whitten (who now works in fisheries management for the state of North Carolina).

“No matter how much you read about things in a textbook, a lot of concepts in geology just don’t click until you see them in real life,” Hage says. “It sparks a lot of excitement in students when they experience the process of scientific discovery in the field.”

“Students get to actually see the connections of the past and the present,” Martin adds. “On the north point of San Salvador, for instance, the undulating landscape consists of ancient sand dunes that turned into rock. We can walk across these ancient dunes to look at the rock record and get an idea of how the island changed over time.”

During a stop on the shoreline road on the south end of the island, Martin happened to notice what looked like the trace of an fossil iguana burrow on a limestone outcrop exposed by a roadcut.

This press release was produced by Emory University. The views expressed here are the author’s own.