Size mattered for flying dinosaurs

Prehistoric flying dinosaurs put even more effort into elaborate mating displays than modern-day peacocks, scientists from Australia and the UK say.

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New research into pterosaurs and pelycosaurs – the fin-backed ancestors of modern mammals – have shown their elaborate headcrests and sails were developed for the purpose of sexual selection.

Until now, many thought these appendages regulated body temperature or, in the case of pterosaurs, such as the giant Pteranodon, they helped them steer while they were flying.

Now a team from the universities of Hull, Portsmouth and WA have found that prehistoric pterosaurs evolved elaborate headcrests to help them attract the best mates while the pelycosaurs, a group of our own distant ancestors, developed fantastic sails along their backs to oust sexual competitors.

The research, published in The American Naturalist, shows how the relative size of the head crest compared to the body of the pterosaur was too big for it to have been dedicated to temperature control.

These findings suggest that the elaborate crests and sails became so grand because of sexual competition.

The study says bigger crests and sails were more attractive to prospective mates so they became more exaggerated over successive generations.

Some pterosaurs had crests five times bigger than their skulls.

The researchers used physics to plot body size against metabolism and found that in each case the size of the crests and the sails were too extreme to have a dedicated body temperature control function.

Lead author Dr Joseph Tomkins, from the University of Western Australia, said: “Our analysis suggests that male Pteranodon either competed with each other, in battles for dominance using their crests – in a similar way to animals with horns or antlers – or alternatively, that females assessed males on the size of their crests, in a similar way to peahens choosing among a group of displaying males.”

Dr Dave Martill, from the University of Portsmouth, said: “Pterosaurs put even more effort into attracting a mate than peacocks whose large feathers are considered the most elaborate development of sexual selection in the modern day. Peacocks shed their fantastic plumage each year, so it’s only a burden some of the time, but pterosaurs had to carry their crest around all the time.”

Dr Stuart Humphries, from the University of Hull, said: “One of the few things that haven’t changed over the last 300 million years are the laws of physics, so it has been good to use those laws to understand what might really be driving the evolution of these big crests and sails.”

He added: “Collecting or dumping heat may well still have been important in these animals, as it is with some today, but we have been able to show that these animals were likely to have been using their crests and sails to mainly to attract mates or deter sexual competitors.”

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