Scientists Identify First Fully Marine Amphibian from Late Triassic China
Fossils of Gerrothorax maritimus, a three-foot, armor-covered amphibian that lived in the sea 230 million years ago, were described by an international research team.
Fossil remains of a previously unknown amphibian species that lived in marine environments during the Late Triassic have been described by scientists from the United States and China. The animal, named Gerrothorax maritimus, measured about three feet in length, had a disc-shaped, heavily armored body and is thought to have inhabited ocean bottom habitats in what is now Guizhou Province.
The discovery is based on two nearly complete skeletons recovered from deep-sea sediments that date to roughly 237 million years ago. Researchers used anatomical analysis and geochemical testing of strontium isotopes to confirm the marine origin of the specimens.
"This area is part of an ecosystem that we've been looking at and trying to reconstruct. We've been mostly studying marine reptiles and the fish from this place, but now we also have this amphibian and it's a sort of very unusual member of the lineage," said study co-author Ryosuke Motani of the University of California, Davis.
Unlike modern amphibians, which are generally restricted to freshwater, Gerrothorax maritimus appears to have tolerated salt water, likely because its bony armor limited water absorption through the skin and its gills could filter out salt. The animal is interpreted as a bottom-dwelling suction feeder, waiting on the seafloor and drawing prey into its mouth, a feeding style compared by Motani to that of the modern carpet shark wobbegong.
The researchers note that among more than 8,000 living amphibian species, none are fully marine and only a small fraction show any salt tolerance. The new find therefore provides the first fossil evidence of a fully marine amphibian, expanding understanding of vertebrate adaptation to ancient oceanic ecosystems.