Pterosaur parenting: How the size of the nestlings affected their development

Scientists have made a fascinating discovery about the parenting behaviors and wing development of small and large pterosaurs, the flying reptiles that lived during the Jurassic and Cretaceous periods. Researchers from Ireland, China, and the U.K. analyzed rare fossils and found an interesting trade-off between the size of the pterosaurs and their need for parental care.

It turns out that small pterosaurs were born with relatively strong and large wings, enabling them to leave the nest swiftly and potentially take flight within a day or two of hatching. This independence likely allowed them to avoid predators and survive on their own.

On the other hand, the larger pterosaurs of the Cretaceous period required more extensive parental protection due to their cumbersome size. As their wingspans increased, reaching up to five meters or even 10-15 meters, the equivalent of a small glider, these larger pterosaurs needed additional care and protection during their early stages.

Despite the differences in parenting strategies, all pterosaurs faced a common limitation: their babies were small because they were restricted by the size of their eggs. The investment in childcare for non-flying babies was balanced out in evolutionary terms, as it allowed these creatures to eventually grow into impressive giants of the sky.

The study’s findings, published in Proceedings of the Royal Society B, shed light on the fascinating interplay between wing development, parental care, and the incredible size diversity of pterosaurs throughout history.

According to lead author Dr. Zixiao Yang from University College Cork, the study on pterosaurs was challenging due to the rarity of baby pterosaur fossils. To gather data, the researchers examined well-preserved specimens from the Jurassic and Cretaceous periods, including classic finds from Europe, North America, and new discoveries from China.

The research focused on allometry, a phenomenon observed in various animals, including pterosaurs, where certain body parts grow at different rates during development. In the case of small Jurassic pterosaurs, they were born with relatively large wings and strong limbs, indicating they could fly from an early age. As they matured, their wings and limbs grew more slowly compared to the rest of their bodies.

However, for the larger Cretaceous pterosaurs, the key limb bones showed positive allometry, meaning they grew at a faster rate during development. This suggests a different developmental model from their smaller counterparts.

The reason behind this difference lies in the parenting strategies of these ancient reptiles. The bird-sized Jurassic pterosaurs had relatively minimal parental care, enabling them to save energy. As a result, they could invest more resources into achieving larger body sizes as adults. On the other hand, the Cretaceous giants required more extended parental care due to their size and the need to protect their young from potential accidents.

The study revealed that both small and large pterosaurs faced limitations in body size due to the constraints of egg size. However, the larger pterosaurs overcame this limitation by adopting a different parental care behavior, allowing them to achieve enormous sizes.

In modern animals like birds and mammals, similar behavior can be observed, where some species have young that can fly or stand shortly after birth, while others require more extended parental care. This behavior involves trade-offs and risks for both the offspring and the parents. The research sheds light on the evolution of pterosaurs and the factors that contributed to their size diversity throughout history.

Source: University of Bristol

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