Monkeydactyl, a pterosaur with an opposable thumb?

Monkeydactyl, a pterosaur with an opposable thumb?


About 160 million years ago, in the Chinese territory known today as Liaoning, a pterosaur with a wingspan of almost a meter, climbed the treetops using its claws, but above all its legs with opposable thumbs. This pterosaur, according to a recent study published by Current Biology, would be the most ancient animal to possess this very important feature!

The Kunpengopterus Antipollicatus, affectionately known as "Monkeydactyl", is one of the three species of the genus Darwinopterus present in the region during the Jurassic period.

Kunpengopterus Antipollicatus

Fossil discovery

The Darwinopterus pterosaurs are named after Charles Darwin due to their anatomical characteristics unique. They are transitional species, with forms that suggest an evolutionary shift between the archaic precursors of pterosaurs, such as lagerpetids, and larger and more familiar species, such as the Pteranodon seen in the films of the Jurassic Park franchise.

Kunpengopterus Antipollicatus is the only darwinopterus in the area believed to have an opposable thumb. This suggests that evolution has led this type of pterosaur to play extremely specific roles within their ecosystem.

Xuanyu Zhou, a paleontologist at the China University of Geosciences, in a press release at the University of Birmingham stated that the results of their research show that Kunpengopterus Antipollicatus occupied a very different ecological niche from those of the other Darwinopterus and Wukongopterus, which probably minimized competition between these pterosaurs.

The opposable toe in this species is, technically, a real "thumb", that is the innermost finger of the front legs. Speaking of modern species, in addition to mammals (and primates in general) this characteristic is shared for example by tree frogs, amphibians, or chameleons, the only current reptiles to possess this particular trait. The opposable thumb is a key trait for arboreal species, as it allows them to cling to branches and climb trees with ease.

To determine, with relative accuracy, whether this particular pterodactyl really possessed an opposable thumb, the team of researchers subjected the only foreleg claw in their possession to an X-ray examination, trying to understand how this finger interfaced with the others.


Illustration by Chuang Zhao

According to what reported by Fion Waisum Ma, paleontologist at the University of Birmingham, the fingers of the Monkeydactyl are tiny and largely "buried" in the rock but, with X-rays, it was possible to see through the solid block of the fossil and thus create a digital model capable of confirming that the "thumb" is articulated in the opposite way to that of the other fingers.

To give credit to the theory than these pterosaurs were really arboreal, the team compared the data collected from fossils with those from other species with this largely ascertained habit, confirming it also for Kunpengopterus Antipollicatus.

However, not all of them are d ' accord with this theory. "An opposable thumb is not a surefire indication of arboreal habits," said Kevin Padian, a paleontologist at UC Berkeley, noting that existing animals, such as raccoons and otters, also have opposable thumbs but do not live in trees and that the results of the researchers relied on the only claw preserved in the fossil, whose position could be distorted by the state of conservation.

“The bottom line, for me, is that the joint surfaces of the sample are too poorly preserved to confirm the presence of a real opposable thumb. I think we should look at better preserved artifacts of this species before jumping to definitive conclusions, ”continued Padian.

The controversy is therefore still open. Did arboreal pterosaurs with opposable thumbs really exist during the Jurassic era? Only new, and better preserved, discoveries will be able to put the word "end" to this question. In the meantime, if you want to know more about pterosaurs, we recommend Pterosaurs: Natural History, Evolution, Anatomy, by Mark P. Witton, available for purchase at this link.

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