Eretmorhipis: Beast of the Week

This week we will be looking at an unusual reptile that swam in the oceans during the Triassic.  Let's check out Eretmorhipis corroldongi!

Eretmorhipis lived in what is now China, during the early Triassic Period, about 250 million years ago.  It measured a little over two feet long from snout to tail and was probably a predator of small marine animals.  The genus name translates to "oar fan" in reference to its wide, flat flippers.  Eretmorhipis was a member of the hupehsuchian order of reptiles, which flourished during the early Triassic and were related to the more well known ichthyosaurs.

Watercolor life reconstruction of Eretmorhipis by Christopher DiPiazza.

Eretmorhipis had a long, tube-like body that was reinforced with thick overlapping ribs and extensive gastralia (belly ribs).  Its front limbs were modified into proportionally huge, wide flippers.  Its back limbs were also flippers but were a little smaller in comparison.  These paddle-like limbs no doubt helped Eretmorhipis propel itself through the water with the help of its tail, which would have also been powerful in life.  Eretmorhipis also had ten bony plates, called osteoderms, in a line down its back.  These may have helped it protect itself from predators, or perhaps were used in some sort of combat within the species.  They also may have helped regulate body temperature, by acting like solar panels to absorb more heat from the sun. Modern reptiles, like crocodilians and turtles, have been known to use their bony armor for all these purposes.

Photo of the latest uncovered specimen of Eretmorhipis, which preserved the skull, showcasing the unusual bill-like snout.

Eretmorhipis' head was proportionally tiny compared to the rest of its body.  Furthermore, it had proportionally tiny eyes compared to the rest of the head!  It also had a long flattened bill-like mouth that squared off at the tip, very similar to that of modern platypus.  Platypus also have tiny eyes, and therefore poor eyesight.  Even though the platypus is not closely related to Eretmorhipis, it may give us clues to help determine how the prehistoric reptile may have hunted.  If it was similar to the platypus, it may have relied on other senses, instead of sight, and sifted around in the mud and sand underwater with its bill to look for small aquatic prey, possibly invertebrates, to snap up and eat.

References

Xiao-hong Chen; Ryosuke Motani; Long Cheng; Da-yong Jiang; Olivier Rieppel (May 27, 2015). "A New Specimen of Carroll's Mystery Hupehsuchian from the Lower Triassic of China". PLoS ONE. 10 (5): e0126024. 

Long Cheng, Ryosuke Motani, Da-yong Jiang, Chun-bo Yan, Andrea Tintori, Olivier Rieppel. Early Triassic marine reptile representing the oldest record of unusually small eyes in reptiles indicating non-visual prey detection. Scientific Reports, 2019