Tiny eyes make a bizarre, ancient platypus-like reptile even weirder

The creature lived about 250 million years ago

ancient marine reptile

SMALL-EYED SWIMMER  Two new fossils of the ancient marine reptile Eretmorhipis carrolldongi (one shown at top; outline below) are the first to include the animal’s skull.

L. Cheng et al/Scientific Reports 2019

My, what tiny eyes you had, Eretmorhipis carrolldongi.

Two newly found specimens of the mysterious, platypus-like reptile suggest that the ancient creature had very small eyes for its size, and may have hunted mainly by touch. That makes E. carrolldongi the oldest known amniote — a group that includes reptiles and mammals — to use a sense other than sight to find its prey, scientists report online January 24 in Scientific Reports.

E. carrolldongi, which lived about 250 million years ago, is one of numerous strange creatures dating to the Early Triassic described by scientists in recent years. It is part of an oddball array of marine reptiles called Hupehsuchia that lived in a vast lagoon spanning hundreds of kilometers across what’s now central China. That flourishing of forms, which came on the heels of the mass extinction at the end of the Permian Period 252 million years ago, suggests that marine reptiles diversified millions of years earlier than once thought, the researchers say.

E. carrolldongi was named in part for its large, fan-shaped flippers, which give its body a passing resemblance to a platypus (Eretmorhipis means “oar fan”). Now, the newly discovered specimens, the first with skulls, point to one more thing that the ancient swimmer had in common with the modern platypus: very small eyes.

The creature also had a small head, meaning that it probably didn’t use hearing to forage, given the challenge of localizing sound in water. Chemoreception — used by snakes, for example, to gather information from the atmosphere through their tongues — is also unlikely based on the lack of certain telltale holes the skull, say paleontologist Long Cheng of the Wuhan Centre of China Geological Survey and colleagues.

By elimination, the researchers suggest that E. carrolldongi probably used tactile cues, such as hair cells that can help an animal detect movement, to stalk its lagoon prey. Still, electroreception, in which predators sense electric fields generated by moving prey, can’t be ruled out, the scientists say. And that would be one more thing it had in common with platypuses — they use electroreception, too.

Carolyn Gramling is the earth & climate writer. She has bachelor’s degrees in geology and European history and a Ph.D. in marine geochemistry from MIT and the Woods Hole Oceanographic Institution.

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