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Ground Movements Key to Pterosaur Evolution

Palaeontologists at the University of Leicester have made significant strides in understanding the evolutionary adaptations that enabled ancient pterosaurs to achieve remarkable sizes. These insights shed new light on how the ability to walk efficiently on the ground was instrumental in the growth of these prehistoric flying reptiles, some of which boasted wingspans reaching up to 10 meters.

Published in a recent study in Current Biology, the research team explored the characteristics of pterosaur hands and feet from various species spanning their evolutionary history. This examination revealed a level of anatomical variation akin to what is observed in modern birds, suggesting that pterosaurs were not solely aerial predators but also adapted to diverse terrestrial habits—from arboreal to ground-dwelling functions.

Pterosaurs were the first vertebrates capable of sustained flight, showcasing some of the most extraordinary adaptations seen in the history of life. Their reign in the skies during the Mesozoic era (252-66 million years ago) is well-documented; however, this new research highlights a surprising range of terrestrial behavior when these creatures were not aloft.

Adaptations for Climbing and Ground Living

Robert Smyth, the lead author and doctoral researcher within the Centre for Palaeobiology and Biosphere Evolution, pointed out that early pterosaurs were particularly adapted for climbing, exhibiting specialized features in their hands and feet similar to those of climbing lizards and certain birds today. He noted, “Clinging to vertical surfaces for extended periods is particularly challenging for larger animals, making small, lightweight forms more efficient for such lifestyles.”

Initially, early pterosaurs likely thrived in forested environments, resulting in smaller body sizes. However, a pivotal evolutionary transition occurred during the Middle Jurassic period. Pterosaurs’ anatomical features evolved to resemble those of terrestrial animals, facilitating ground movement and opening vast ecological opportunities. This shift eliminated the size limitations of their previous, arboreal lifestyles, allowing some species to grow to colossal proportions.

From Flight to Ground Mobility

Co-author Dr. David Unwin elaborated on these distinctions, explaining that early pterosaurs had hind limbs connected by a flight membrane which hampered their terrestrial locomotion. As evolution progressed, this membrane transitioned to allow for independent movement of the hind limbs, which was a crucial adaptation that, along with alterations in hand and foot structure, significantly improved mobility on solid ground.

“Liberated from the climbing constraints, these later pterosaurs were able to evolve to substantial sizes and became some of the most formidable giants of their time,” Dr. Unwin remarked.

Structural Changes in Extremities

The morphological changes in the hands and feet of pterosaurs are particularly telling. Early forms exhibited short bones at the bases of their fingers and toes, contrasting sharply with the elongated structures found further from the body, culminating in robust claws ideal for climbing. In later, more derived species, the structure flipped: longer bones at the base and shorter, flatter claws were indicative of an adaptation geared more toward walking than climbing.

Smyth added, “These discoveries emphasize the importance of contemplating all facets of pterosaur locomotion, not merely their capacity for flight. Understanding their terrestrial life sheds light on their ecological roles within ancient ecosystems.”

As pterosaurs adapted to life on land, they entered a habitat already occupied by numerous dinosaurs and reptiles. Enabling their survival, pterosaurs strategically navigated around competition by exploiting diverse ecological niches that required both aerial and terrestrial capabilities. This innovative approach led to the development of unique feeding mechanisms, including an evolution of fine, needle-like teeth suited for filter feeding—a trait reminiscent of modern flamingos, and astonishingly emerging over 120 million years before flamingos themselves appeared.

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