Ancient armored bottom-feeder is first seagoing amphibian

Key Points:

• Researchers have discovered Gerrothorax maritimus, an amphibian species that lived fully in the sea about 237 million years ago during the Triassic Period, marking the first known marine amphibian.
• This amphibian had a flat, disc-shaped, armored body and a wide mouth adapted for bottom-dwelling suction feeding, preying on fish, worms, and cephalopods in a muddy seafloor environment.
• Gerrothorax maritimus evolved from armored freshwater ancestors, with its body armor likely serving as protection against seawater, enabling it to survive in a fully marine habitat despite amphibians' typical intolerance to saltwater.
• The discovery challenges previous understanding since amphibians generally rely on permeable skin for breathing and drinking, which is incompatible with seawater due to osmotic water loss, making this species a unique example of exaptation.
• Chemical analysis of the fossils confirms the animal developed and grew in the ocean, coexisting with large marine reptiles like ichthyosaurs, and demonstrating a previously unknown amphibian adaptation to marine life.