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Drepanosaurs!

Recently, I talked about Sharovipteryx, a strange-looking animal belonging to Protorosauria. The protorosaurs were relatives of the archosaurs that lived from the Early to Middle Triassic period, and occupied roles similar to modern lizards and other small reptiles. One particular group of protorosaurs was quite striking in its resemblance to a modern group of animals, and yet remained one of the strangest groups of reptiles to ever walk the earth.

The drepanosaurs lived for a very short time - only about four million years during the Late Triassic - but were already highly specialized for tree-dwelling lifestyles. They are characterized by their prehensile tails, which were often tipped with sharp, claw-like hooks of bone, believed to have aided in climbing. They also possessed a “hump” of fused vertebrae in between their shoulder blades - an attachment point for powerful neck muscles, allowing their heads to quickly strike forward and snatch up unwary insects.

In terms of their lifestyles and adaptations, drepanosaurs closely resembled chameleons - a group of reptiles to which they were not closely related, and which would not evolve for at least 160 million years.

Only a few species of drepanosaurs are known, but all of them possess uniquely strange features. Megalancosaurus, pictured above, had thumb-like opposable toes found only in some individuals - possibly a sexually dimorphic trait, used by either males or females to strengthen their grip during mating. Drepanosaurus, pictured below, had a massively distended claw on its index finger, possibly used to tear open tree bark or insect nests.

(Both above reconstructions by Nobu Tamura.)

Hypuronector is so divergent from its drepanosaur relatives that it is currently classified in its own unique sister group. Its flattened, paddle-like tail suggests that it may have been aquatic rather than arboreal. However, no complete skeleton has yet been found.

(Reconstruction by Smokeybjb, showing Hypuronector as an arboreal animal.)

Due to their extremely derived and strange anatomy, classification of the drepanosaurs has been difficult. It’s currently believed that they’re closely related to the other arboreal protorosaurs, such as Sharovipteryx, as well as the long-necked tanystropheids.

#protorosaurs #drepanosaurs #Drepanosaurus #Megalancosaurus #Hypuronector #Triassic