DINOSAURS evolved fancy head crests and sails along their backs to attract mates, according to a new study by the University of WA (UWA).

UWA researcher Joseph Tomkins says pteranodon crests and eupelycosaur sails are among the earliest and most extreme examples of elaborate sexual signals in the evolution of terrestrial vertebrates.

Until now, brightly plumed peacocks were regarded as the animal kingdom’s biggest showoffs, the beautiful plumage of the male birds used to attract mates.

To attract a female, a male performs a mating dance while displaying its bright feathers and calling loudly. Males may perform these displays alone or in competitive groups.

The female peacock’s choice appears to be based on the strength of the display of the male and condition and colour of his feathers. The strongest, most brightly-feathered males have a better chance of being chosen.

Dr Tomkins and colleagues at both Hull and Portsmouth universities in the UK believe the crested pterosaur pteranodon ongiceps evolved elaborate headcrests while the sail-backed eupelycosaurs dimetrodon and edaphosaurus had decorative sails on their spines to attract mates.

Previously, scientists thought these physical characteristics were associated with thermal regulation. However, the latest study published in The American Naturalist found the size of the pterosaur’s head crest was too big to play a role in temperature control.

“This orthodoxy persists despite the observation that traits exaggerated to the point of impracticality in extant organisms are almost invariably sexually selected,” the study’s authors say.

“Furthermore, small ancestral, sail-backed pelycosaurs would have been too small to need adaptations to thermoregulation.”

The team plotted scaling relationships between metabolism and body size for each of the animals.

They linked bigger crests and sails to sexual competition, with features becoming more exaggerated over time.

The plate-backed stegosaurus may have developed elongated features to attract others. Numerous species, including the head-crested hadrosaurs and sail-backed eupelycosaurs dimetrodon and edaphosaurus also sported strange structures.

“The sails of the eupelycosaurs are among the earliest known examples of exaggerated secondary sexual traits in the history of vertebrate evolution,” Dr Tomkins says.

“Indeed the sail of dimetrodon is one of the largest secondary sexual traits of any animal.”

Since a large crest or sail would be considered a desirable trait, over the generations these parts of the body increased in size. Some pterosaurs had head crests five times bigger than their skulls.

Dr Tomkins says the analysis suggests male pteranodons either competed with each other in battles for dominance or displayed their wares to the females.