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Was it a sea-lamander?
Scientists have discovered the first-ever fossil evidence of sea-dwelling amphibians, potentially upending everything we know about the animal class.
“It’s a sort of very unusual member of the lineage,” co-author and paleontologist Ryosuke Motani, of the University of California, Davis, said in a statement.
Dubbed Gerrothorax maritimus, the amphibian in question was a three-foot-long, chonky critter that resided on the bottom of the ocean, per the study in Nature Ecology and Evolution.
This theory stemmed from an analysis of two nearly complete, 237-million year-old skeletons that were unearthed in a region of China once covered in ocean.
During this period in the Late Triassic, this aquatic ecosystem was inhabited by turtles, icthyosaurs and other species of marine reptiles.
Nonetheless, the ocean denizen was an anomaly as none of the 8,000 species of modern amphibians are known to reside in salt water.
Meanwhile, fewer than 2% can tolerate salinity on account of their porous skin, which is essential for gas and water exchange, Science Alert reported.
There had also been no recorded evidence of a prehistoric, seafaring amphibian — until now.
As the specimens in question were located nearly 19 miles from the closest islands, researchers theorized that the ancient amphibians spent their entire lives at sea.
This would make them an extreme outlier in the amphibian class, which is defined by the ability to navigate both land and water.
How does a typically freshwater-reliant creature survive in a marine environment?
The researchers cited the amphibian’s bony carapace, which, along with protecting them against predators like ichthyosaurs, prevented maritimus from absorbing saltwater through its skin.
Instead, this oceanic salamander drank the water through its mouth and filtered it with its digestive system, posited the researchers, who suspected that the gills would’ve helped maritimus sift out the salt.
The amphibian’s formidable armor and squat head shape also suggested that the species was an ambush predator that relied on suction to hoover up food animals.
“They would probably just wait at the bottom and then when prey comes around, they would just suck it in,” said Motani, who said it was of a similar size to a giant salamander but “really chunky” instead of long.
This build would’ve further hindered the nautical newt’s ability to move on land.
The researchers considered the possibility that the skeletons were swept out to sea post-mortem, but ultimately dismissed this hypothesis due to the intact nature of the remains.
“Carcasses at sea, unless they sink to the bottom right away, tend to dry out and lose limbs prior to sinking to the bottom,” said Motani. “But these animals had their fingers preserved, so that means they probably died near where they lived.”
Subsequent testing revealed that the levels of strontium — a trace element that easily amasses in animal bones — found in the fossil mirrored those commonly observed in the oceans of the Late Triassic.