Small pterosaurs are born with relatively strong, large wings, which means they can leave the nest quickly, while the energetic baby large pterosaurs need parental protection from predators, scientists have discovered.
A group of researchers from Ireland (University College Cork), China (Nanjing and Yunnan Universities) and the UK (University of Bristol and Queen Mary University of London) analyzed rare fossils to show that there was an evolutionary trade off between increased parenting and increased size of flying reptiles.
Their findings, published on July 19 under the title “Allometric wing growth links parental care to pterosaur giantism” in Proceedings of the Royal Society Brevealed that the tiny Jurassic pterosaur babies already had large and strong wings when they hatched from their eggs and could flutter in flight perhaps within a day or two of birth.
However, in the Cretaceous, pterosaurs were larger, with wingspans of five meters being the norm. Some later pterosaurs reached 10–15 meters, the size of a small glider, and larger than any known bird.
The young of all pterosaurs, large and small, are small, limited in egg size. Investing in child care by having non-flying children is traded in evolutionary terms for allowing them to grow into giants in the sky.
“This is a difficult project,” said lead author, Dr. Zixiao Yang from University College Cork. “We need to find examples of pterosaurs where we have at least one hatchling or very young specimen as well as adults so we can study their relative growth rates. In most cases, “Delicate skeletons are incomplete. Baby pterosaurs are rare.”
“Fortunately, we were able to use some classic specimens from the Jurassic of Europe and the Cretaceous of North America, along with new finds from China,” said Professor Baoyu Jiang from Nanjing University. “By measuring skulls, spines, wings, and hind legs, we have data to assess differences in the relative growth of different body parts.”
Professor Michael Benton from Bristol’s School of Earth Sciences said, “The study is about allometry.
“We are familiar with the allometry of human infants, puppies and kittens whose heads, eyes and knees are very large, and the rest of the body grows faster to reach adult proportions. It is the same as many animals, including dinosaurs and pterosaurs. Babies also have cute faces, with short noses, big eyes, and generally big heads.”
“Bird-sized Jurassic pterosaurs were born with relatively large wings and critical, powerful arms and legs, evidence that the young could fly from birth,” added collaborator Professor Xu Xing at Yunnan University. “As they grow from infancy to adulthood, their arms and legs show negative allometry, meaning they start out big and then grow more slowly than the rest of the body.”
“But it was different for the Cretaceous giants,” explains Professor Maria McNamara of University College Cork. “They also start as young children, but the key bones of the foot show positive allometry through growth, suggesting a very different developmental model.”
“This means that the pterosaur giants sacrificed low-input childcare to the need to grow large as adults,” said Dr. David Hone of Queen Mary College London. “Little childcare is reasonable as a starting point for these ancient reptiles because it saves them energy. But to grow big, the bigger pterosaurs have a problem, which is a longer time which is necessary to become an adult, and the need to protect their youth from accidents.
“The babies of all pterosaurs, big and small, are small because of egg size limitations. The investment in childcare by having flightless babies is compensated in evolutionary terms by releasing a restraint to be truly great.”
Dr. Zixiao Yang concluded, “We see the same thing in birds and mammals today. Some birds fly very young, and of course some mammals like cows and antelopes are on their feet during the day. they are born. But this type of behavior is dangerous for the babies because they are usually clumsy and easy targets for predators, also costly to the mother because the babies must have long wings or legs at the point of birth. forbidden- an of the maximum body size until the end of the Jurassic, where their behavior of parental care changed, and then they can reach large sizes.
Zixiao Yang et al, Allometric wing growth links parental care to pterosaur giantism, Proceedings of the Royal Society B: Biological Sciences (2023). DOI: 10.1098/rspb.2023.1102
Provided by the University of Bristol
Citation: Large pterosaurs were better parents than their smaller, earlier counterparts, study finds (2023, July 19) Retrieved July 19, 2023 from https://phys.org/news/2023-07- large-pterosaurs-parents-smaller-earlier. html
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