China fossil may show first amphibian to live entirely at sea
A 237-million-year-old fossil of Gerrothorax maritimus suggests the species lived in a marine environment.
Researchers have identified a fossil from China that may provide evidence of a stem amphibian living entirely in the sea. The species, named Gerrothorax maritimus, dates back to the Late Triassic period approximately 237 million years ago.
The two nearly complete skeletons were found in deep-sea sediments in Guizhou Province. Measuring about 74 centimetres or 2.4 feet in length, the creature had a disc-shaped body protected by bony plates.
Scientists believe the animal was a bottom-dweller that fed by sucking in small animals. Its protective armour may have shielded it from predators like ichthyosaurs found in the same region.
The study, published in Nature Ecology & Evolution, notes that most amphibians cannot survive in saltwater due to permeable skin. Researchers suggest the bony covering of Gerrothorax maritimus may have restricted water and salt movement through its skin.
Geochemical tests on the bones showed strontium isotope ratios that match seawater from the Late Triassic period. This supports the conclusion that the animals lived in the ocean rather than being carried there after death.
The species is thought to have descended from a lineage of armoured amphibians that lived in freshwater. This discovery suggests that existing evolutionary features may have allowed the group to adapt to new environments.
