New research by paleontologists from the University of Leicester, the University of Birmingham and Liverpool John Moores University demonstrates an unexpectedly high degree of variation in the hands and feet of pterosaurs, comparable with that observed in living birds. The discovery indicates that pterosaurs were not confined to a life in the skies but were also adapted to a wide range of terrestrial lifestyles, from tree-climbing in early species to more ground-based lifestyles in later ones.
Pterosaurs, the first true flying vertebrates, played a crucial role in Mesozoic terrestrial ecosystems.
However, current understanding of their ability to move around on the ground and, more broadly, their terrestrial paleoecology is limited.
“Early pterosaurs were highly specialised for climbing, with extreme modifications in their hands and feet, similar to those found in climbing lizards and birds like woodpeckers today,” said Robert Smyth, a doctoral researcher at the University of Leicester.
“Clinging to vertical surfaces by your fingertips for long periods is hard work — it’s a lot easier for small, lightweight animals.”
“These early pterosaurs were likely restricted to arboreal habitats and consequently, small body sizes.”
“However, a major evolutionary shift occurred during the Middle Jurassic period, when pterosaur hands and feet changed to look much more like those of ground-dwelling animals.”
“These adaptations to ground-based movement opened up new ecological opportunities, leading to a wide variety of feeding strategies.”
Freedom from the size constraints imposed by vertical living allowed some pterosaurs to evolve to gigantic size with wingspans of up to 10 m.
“In early pterosaurs the hind limbs were connected by a flight membrane which severely impeded walking and running,” said Dr. David Unwin, a researcher at the University of Leicester.
“In later, more advanced pterosaurs, this membrane became separated along the midline, allowing each hind limb to move independently.”
“This was a key innovation that, combined with changes to their hands and feet, greatly improved pterosaurs’ mobility on the ground.”
“Freed from the constraints of climbing, these later pterosaurs could grow to enormous sizes, with some species becoming true giants of the Mesozoic.”
In early pterosaurs, the bones at the base of the fingers and toes were relatively short, while those farther from the body were greatly elongated, ending in large, curved claws — together these modifications resulted in a powerful grip — ideal for climbing.
By contrast, later, more advanced pterosaurs showed the opposite pattern: the bones at the base of their fingers and toes were much longer, while those closer to the tips were shorter.
Their claws were also flatter and less curved, suggesting they were better adapted for walking rather than climbing.
“These findings underscore the need to examine all aspects of pterosaur locomotion, not just flight, to fully understand their evolution. That pterosaurs could fly is only one part of their story,” Smyth said.
“By exploring how they lived in the trees or on the ground, we can begin to understand the roles that they played in ancient ecosystems.”
“When pterosaurs arrived on the ground, it was already inhabited by a wide range of animals, including dinosaurs and many other reptiles.”
“Pterosaurs cleverly avoided competition with these established groups by exploiting ecological niches that required both flying and walking abilities.”
“This resulted in some bizarre feeding strategies such as evolving hundreds of fine, needle-like teeth that were used for filter-feeding.”
“This remarkable feature, resembling the feeding method of modern flamingos, emerged at least 120 million years before the first flamingos evolved.”
The study was published in the journal Current Biology.
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Robert S.H. Smyth et al. Hand and foot morphology maps invasion of terrestrial environments by pterosaurs in the mid-Mesozoic. Current Biology, published online October 4, 2024; doi: 10.1016/j.cub.2024.09.014
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