Where did the drepanosaurs go?

If you ever wondered what you get if you crossed a lizard, a monkey, a Velociraptor and a bird (presumably after taking some mind-altering drugs), it would probably look something like a drepanosaur. Drepanosaurs were a group of lizards whose fossils date to between 221.5–201.6 million years ago [1]. They have been found in rocks ranging from Italy and England to New Jersey and the American Southwest.

Drepanosaurs were distinct in having bird-like skulls, including beaks and a shoulder hump formed by the fusion of vertebrae. Some of them had hands with only two fingers, prehensile tails, which are capable of acting like a fifth limb by wrapping around objects, and even a large claw-like structure at the tip of the tail. These latter traits are particularly useful for  climbing in trees, suggesting this may be where many drepanosaurs spent their time.

The prehensile tail is very apparent in Vallesaurus (left) and Drepanosaurus (right). The claw-like tip is particularly apparent in the Drepanosaurus specimen.

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Drepanosaurus (above) had a large claw on its index finger, analogous to the giant toe claw in Velociraptor. The claw may have been used to tear through bark to obtain insect prey.

432megalancosaurus

Some individuals of the species Megalancosaurus had opposable digits, similar to chameleons, which would have allowed them to wrap their hands and feet around branches.

Hypuronector

Some researchers speculate that Hypuronector may have been aquatic based on its deep, newt-like tail, which might have been useful for swimming, and the fact that it was discovered at the bottom of an ancient lake. Here, however, it is imagined as a tree-dwelling species.

Since we do not know very much about drepanosaurs, especially due to their apparently low diversity, it’s difficult to test why they went extinct. However, it is noteworthy that their disappearance appears to have coincided with the Triassic-Jurassic extinction event when half of all known species died out. It’s unclear what led to this mass extinction, though it may have been due to volcanism, climate change and/or meteor impact.

Whatever reason it might have been, certainly the earth has been robbed of one of its strangest groups of creatures.

Questions for Creationists

Where did the drepanosaurs go? Shouldn’t they have been able to fit on Noah’s ark? If they survived the Flood, how did they cross the Atlantic Ocean to America?

References

1. Paleobiology database

Photo credit

Vallesaurus, Drepanosaurus, MegalancosaurusHypuronector

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