Pterosaurs had good parenting skills, but only the larger species

Scientists from globally renowned institutions in Ireland, China, and the UK have unearthed new insights into the parenting habits of the prehistoric flying reptiles, the pterosaurs. These creatures roamed the skies during the era of the dinosaurs, and their parental instincts have long intrigued the scientific community.

A collaboration between researchers at University College Cork (UCC), Nanjing University, Yunnan University, the University of Bristol, and Queen Mary University of London has led to the surprising conclusion that pterosaurs did, in fact, exhibit parental care, but only within the larger species.

These findings offer solutions to an ongoing mystery. In order for both birds and pterosaurs to take flight soon after birth, they require sufficiently developed wings.

Earlier studies of smaller, Jurassic-era pterosaurs revealed that hatchlings were born with large wings. This equipped them to flutter into the air within days of emerging from their eggs.

However, this finding raised questions about the pterosaurs’ later relatives. They evolved to be considerably larger.

In the Cretaceous period, pterosaurs typically bore wingspans of about 5 meters. Some even boasted wingspans between 10 and 15 meters, which is roughly the size of a small glider.

How to study pterosaur parenting

Conducting this research was no small feat, according to the project’s lead, Dr. Zixiao Yang from UCC. The team had to find examples of pterosaur parenting in which at least one very young or newly hatched specimen could be compared to adults to study their growth rates. However, infant pterosaurs are incredibly rare.

In collaboration with fellow researchers Professor Baoyu Jiang, Professor Michael Benton, Professor Xu Xing, and Professor Maria McNamara, Dr. Yang undertook the investigation.

With a mix of classic specimens from the Jurassic period in Europe and the Cretaceous period in North America, along with fresh finds from China, the team began their detailed study. They measured the skulls, backbones, wings, and hind legs of their samples.

The allometry of flying reptiles

The scientists focused on analyzing the allometry of these creatures. This refers to how their physical traits changed as they grew larger.

The concept of allometry is common in many animals, including humans, where babies, puppies, and kittens have relatively larger heads, eyes, and knees. As they mature, the rest of the body grows at a faster pace to achieve adult proportions.

“Our findings show that the small, bird-sized Jurassic pterosaurs were born flight-ready, equipped with large wings and robust limbs,” Dr. Yang explained. “Throughout their growth from infancy to adulthood, their limbs displayed negative allometry—meaning they started off large but grew slower compared to the rest of their bodies.”

The story for the Cretaceous-era giant pterosaurs, however, was different. These creatures also began life as tiny hatchlings, but the growth of their key limb bones showed positive allometry, pointing to a contrasting developmental model.

Larger pterosaur species were better at parenting

In essence, this suggests that the giant pterosaurs had to give up low-energy parenting for the ability to grow to considerable sizes as adults. While minimal childcare might have been an energy-saving tactic in the early evolution of these ancient reptiles, the larger pterosaurs faced a unique challenge.

Larger pterosaur species took longer to mature. Consequently, their parents had to protect them from potential accidents. Due to the constraints of egg size, all pterosaur hatchlings, irrespective of whether they were large or small, began life as tiny creatures.

“To allow for the evolution of truly massive sizes, pterosaurs compensated for their investment in childcare by birthing non-flying infants,” Dr. Yang clarified. This behavior is mirrored in certain birds and mammals today. Species like cattle and antelopes are mobile from the day they’re born, while some birds can fly at a very young age.

While this behavior may pose risks to the young—due to their vulnerability to predators and their clumsiness—it’s also costly for the mother, who must ensure that their offspring have well-developed limbs at birth. As with modern animals, extinct pterosaurs faced similar trade-offs. “They were restricted in maximum body size until the end of the Jurassic, at which point their parental care behavior changed, and then they could achieve huge sizes,” Dr. Yang concluded.

More about pterosaurs

Pterosaurs, often referred to as pterodactyls, were an order of flying reptiles that lived from the Late Triassic to the end of the Cretaceous period. They are notable for being among the first vertebrates to evolve powered flight, existing from about 228 to 66 million years ago.

Here’s a more in-depth look at these fascinating prehistoric creatures:

Classification and diversity

Pterosaurs are part of the Archosauria group, which also includes dinosaurs, crocodiles, and birds. However, pterosaurs are not dinosaurs themselves, but a separate and distinct group. They were incredibly diverse, with over 130 known species varying widely in size and form.

Size

The size of pterosaurs ranged from the very small to the gigantic. The smallest pterosaurs like Nemicolopterus were about the size of a sparrow, with a wingspan around 25 centimeters (10 inches).

The largest known pterosaurs, like Quetzalcoatlus and Hatzegopteryx, had wingspans up to about 10-11 meters (33-36 feet), roughly the size of a small airplane.

Physical characteristics

Pterosaurs had a number of unique physical traits. One of the most notable was their wings, which consisted of a membrane of skin, muscle, and other tissues stretching from the ankles or elongated fourth finger to the body.

Unlike bats, which have fully webbed fingers, pterosaurs had a single large wing finger. Pterosaurs also had hollow bones, a trait they shared with the theropod dinosaurs and which greatly reduced their weight.

Flying reptiles

Pterosaurs were the first vertebrates to achieve true powered flight, meaning they could flap their wings to fly rather than just gliding. Their wing structure was complex and highly adapted for flight, with a large surface area that allowed them to create lift.

Diet and lifestyle

Pterosaurs had a wide range of diets and lifestyles. Some were fish eaters, catching their prey while flying low over water.

Others were adapted to eat insects, small dinosaurs, or scavenged carrion. Some fossils even suggest that certain types of pterosaurs may have had a primarily terrestrial lifestyle. Finally, as we learned above, larger pterosaurs spent much of their lives parenting to help their offspring survive and thrive.

Fossil record

Pterosaur fossils are rare because their bones were hollow and fragile, making them less likely to fossilize well. Despite this, fossils have been found all over the world on every continent.

Extinction

Pterosaurs went extinct at the end of the Cretaceous period, about 66 million years ago. This coincides with the Cretaceous-Paleogene extinction event that also wiped out all non-avian dinosaurs.

It’s generally believed that a combination of environmental changes, possibly triggered by a large asteroid or comet impact, led to their extinction.

Parental care

Recent studies suggest that at least some pterosaurs may have provided parental care to their young, similar to modern birds. However, as with many aspects of pterosaur biology, this is still a topic of ongoing research and debate.

Despite sharing the skies with the ancestors of modern birds, pterosaurs were a unique lineage of flying animals, distinct from both birds and bats. Today, they continue to fascinate scientists and the public alike as we learn more about their biology and place in Earth’s history.