Uriona says that during the Triassic Period, which began 250 million years ago, the crocodilian ancestors of alligators were cat-sized animals that lived only on land.
Until now, it was believed the diaphragmatic muscle evolved to help them breathe and run at the same time, he says. Showing they are actually using it to move around in water gives an alternative explanation for why the muscle evolved.
It also suggests the muscle didnt evolve until after crocodilians took to the water during the Cretaceous Period, which began 145 million years ago. During that time alligators ancestors also evolved a flattened skull, shorter limbs and a big tail.
Studying the Crocodile Rock
The study involved five, 2-year-old American alligators (Alligator mississippiensis) from Louisianas Rockefeller Wildlife Refuge near Grand Chenier. The gators were only 15 inches to 20 inches long, compared with adults that can reach 15 feet.
Electrodes were implanted on five sets of muscles so their activity could be monitored while the alligators maneuvered in 100-gallon fish tanks. One set of muscles played no role in moving the lungs to help the gators dive and maneuver, but four did:
|Contact: Lee Siegel|
University of Utah