Hairy Museum of Natural History

A new reptile described in this month’s volume of Naturwissenschaften is the first member of its extended family to show adaptations for life in the sea. Qianosuchus mixtus was a 10-foot long carnivore that hunted fish and other reptiles in the shallow seas that covered China 240,000,000 years ago.

Qianosuchus, whose name means “Crocodile from Guizhou Province”, was an archosaur. The Archosauria are a diverse group of reptiles whose members include crocodiles, dinosaurs, and birds. Archosaurs first evolved as terrestrial and freshwater predators around 250 million years ago, but several lineages have expanded into the marine realm over the group’s long history. Crocodilians, for example, have made at least four different forays into the ocean, and one Jurassic group even went so far as to lose all their armor and modify their arms and legs into flippers. And archosaurs are still at it: a couple types hunt in today’s oceans as well.

But Qianosuchus, who branched off from the line that eventually led to crocodiles, was hunting in the oceans during the Middle Triassic, a good 40 million years before any other archosaur picked up the habit.

Rough skeletal reconstruction of Qianosuchus mixtus. Click on the image for a larger version.

To aid it in its maritime excursions, Qianosuchus sported a deep tail that propelled it through the water. Although its ancestors were protected by bony armor, Qianosuchus reduced its armor to a couple of rows of small osteoderms over its neck and trunk. Its long snout was filled with interlocking, daggerlike teeth for catching fish and other slippery prey. And long, slender ribs in its neck would have anchored muscles that allowed Qianosuchus to strike underwater with devastating force.

Still, Qianosuchus wasn’t totally committed to aquatic life. Its hindlimb was long and well-developed for running. It appears to have had a fairly erect gait, like many other terrestrial archosaurs at the time. Its describers envision Qianosuchus as a near-shore predator, running down prey on the beaches and in the shallows, and using its tail to swim after prey in the deeper water.

A few months ago, scientists described Effigia, an early relative of crocodiles with features that bird-like dinosaurs would independently develop millions of years later. Now we know Qianosuchus, another Triassic archosaur with surprisingly advanced features for marine predation. Neither of these animals left any known descendants, but both shared features with younger, distant relatives. The evolution of the Archosaurs is turning into a much more interesting story than anyone might have predicted.

Chun Li, Xiao-chun Wu, Yen-nien Cheng, Tamaki Sato, Liting Wang, An unusual archosaurian from the marine Triassic of China, Naturwissenschaften, Volume 93, Issue 4, Apr 2006, Pages 200 - 206.

—Matt Celeskey.

File under: Recent Discoveries, Reptiles, Triassic.