According to new research, American alligators (Alligator mississippiensis) have remained virtually untouched by evolutionary change for at least 8 million years — up to 6 million years older than previously thought.

“If we could step back in time 8 million years, you’d basically see the same animal crawling around then as you would see today in the Southeast,” said lead researcher Dr. Evan Whiting, from the University of Minnesota.

“Even 30 million years ago, they didn’t look much different,” he added.

“We were surprised to find fossil alligators from this deep in time that actually belong to the living species, rather than an extinct one.”

He and his colleagues describe the alligator as a survivor, withstanding sea-level fluctuations and extreme changes in climate that would have caused some less-adaptive animals to rapidly change or go extinct.

The scientists began re-thinking the alligator’s evolutionary history after Dr. Whiting examined an ancient alligator skull, originally thought to be an extinct species, unearthed in Marion County, Florida, and found it to be virtually identical to the iconic modern species.

They compared the ancient skull with dozens of other fossils and modern skeletons to look at the whole genus and trace major changes, or the lack thereof, in alligator morphology.

The authors also studied the carbon and oxygen compositions of the teeth of both ancient alligators and the 20- to 25-foot extinct crocodile Gavialosuchus americanus that once dominated the Florida coastline and died out about 5 million years ago for unknown reasons.

“The presence of alligator and Gavialosuchus fossils at several localities in north Florida suggest the two species may have coexisted in places near the coast,” Dr. Whiting said.

Analysis of the teeth suggests, however, that Gavialosuchus americanus was a marine reptile, which sought its prey in ocean waters, while alligators tended to hunt in freshwater and on land. That doesn’t mean alligators weren’t occasionally eaten by the marine crocs, though.

“The gators we see today do not really compete with anything, but millions of years ago it was not only competing with another type of crocodilian, it was competing with a much larger one,” said co-author Dr. David Steadman, from the Florida Museum of Natural History at the University of Florida (UF).

“The presence of the ancient crocodile in Florida may have helped keep the alligators in freshwater habitats, though it appears alligators have always been most comfortable in freshwater.”

“While modern alligators do look prehistoric as they bake on sandbars along the Suwannee River or stroll down sidewalks on the UF campus, they are not somehow immune to evolution,” the researchers said.

“On the contrary, they are the result of an incredibly ancient evolutionary line.”

“The group they belong to, Crocodylia, has been around for at least 84 million years and has diverse ancestors dating as far back as the Triassic, more than 200 million years ago.”

The scientists reported their results in a pair of papers in the Journal of Herpetology and the journal Palaeogeography, Palaeoclimatology, Palaeoecology.

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Evan T. Whiting et al. 2016. Cranial Polymorphism and Systematics of Miocene and Living Alligator in North America. Journal of Herpetology 50 (2): 306-315; doi: 10.1670/15-023

Evan T. Whiting et al. 2016. Paleoecology of Miocene crocodylians in Florida: Insights from stable isotope analysis. Palaeogeography, Palaeoclimatology, Palaeoecology 451: 23-34; doi: 10.1016/j.palaeo.2016.03.009

This article is based on a press-release from the University of Florida.