Baby pterosaurs flew the nest straight after hatching, study claims

Extinct flying reptiles called pterosaurs were likely able to fly out of the nest straight after hatching, a new study claims.  

A team of researchers led by a University of Southampton expert performed computer modelling based on the fossils of several pterosaur species.

They conclude that pterosaur hatchlings were agile and ‘flightworthy from the moment of hatching’ – known in biology as precociality. 

The hatchlings had wingspans of almost 10 inches (25cm) attached to bodies that ‘could neatly fit in your hand’. 

Amazingly, the humerus bone in the hatchlings’ wings were stronger than those of many adult pterosaurs, indicating that they were well primed for flight.

Newly-born pterosaurs were also more nimble flyers compared with adults, but less adept at travelling long distances, the team say. 

Pterosaurs weren’t dinosaurs, but a group of flying reptiles that lived during the Triassic, Jurassic and Cretaceous Periods (228 to 66 million years ago). 

They were the earliest reptiles to evolve powered flight, dominating the skies for 150 million years before their extinction some 66 million years ago.

The less well-known cousins of dinosaurs, the ‘flamingo-like’ reptiles had an adept flying ability, some as large as a fighter jet and others small like a model aeroplane.  

The study has been led by Darren Naish, a British vertebrate palaeontologist at the University of Southampton.   

‘Juvenile pterosaurs were capable of powered fight early in life, plausibly within days or hours of hatching,’ they say in their paper. 

‘It seems reasonable to interpret juvenile pterosaurs as neither nest-bound, nor helpless and dependent upon their parents. 

Study author Dr Mark Witton from the University of Portsmouth said scientists have only had fossils of their embryos and hatchlings to study since 2004.  

‘We’re still trying to understand the early stages of life in these animals,’ he said. ‘One discussion has centred around whether pterosaurs could fly as hatchlings or, like the vast majority of birds and bats, they had to grow a little before they could take wing.

‘We found that these tiny animals – with 25 cm wingspans and bodies that could neatly fit in your hand – were very strong, capable fliers.

‘Their bones were strong enough to sustain flapping and take-off, and their wings were ideally shaped for powered – as opposed to gliding – flight.’

However, the hatchlings would not have flown exactly like their parents simply because they were so much smaller. 

‘Flight capabilities are strongly influenced by size and mass,’ Dr Witton said.

‘So pterosaur hatchlings, being hundreds of times smaller than their parents, were likely slower, more agile fliers than the wide-ranging (but less manoeuvrable) adults.’

Competing views exist on the behaviour and lifestyle of pterosaurs during their first moments after birth, according to the team. 

A ‘flap-early’ view proposes that hatchlings were capable of independent life and fapping fight – a theory this study supports. 

Meanwhile, a ‘fly-late’ model suggests juveniles were not fight capable until 50 per cent of adult size, and a ‘glide-early’ model says young juveniles were fight-capable but only able to glide.    

Due to the rarity of fossilised pterosaur eggs and embryos, and difficulties distinguishing between hatchlings and small adults, it has been unclear if newly-hatched pterosaurs were able to fly.

So the researchers modelled hatchling flying abilities using previously obtained wing measurements from four established hatchling and embryo fossils from two pterosaur species, Pterodaustro guinazui and Sinopterus dongi. 

The authors also compared these wing measurements with those of adults from the same species and compared the strength of the humerus bone – which forms part of the wing – of three hatchlings with those of 22 adult pterosaurs.

Not only were the hatchlings’ humerus bones stronger than those of many adult pterosaurs, but the hatchlings had long, narrow wings suited to long-distance flight.

However, their wings were shorter and broader than those of adult pterosaurs, meaning they weren’t as adept at flying long distances as their parents. 

Hatchlings also had a larger wing area relative to mass and body size, compared with the pterosaur adults. 

These wing dimensions may have may also have made hatchlings less efficient than adult pterosaurs at long-distance travel, but may have resulted in them being more agile fliers, enabling them to suddenly change direction and speed.

The authors speculate that the agile flying style of hatchling pterosaurs may have let them rapidly escape predators and made them better suited to chasing nimbler prey and flying amongst dense vegetation than adult pterosaurs. 

This could indicate that pterosaurs occupied dense habitats as hatchlings and open environments as adults, according to the authors.  

The study has been published in Scientific Reports.