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Dinosaurs `dressed to impress mates`

Dinosaurs evolved fancy head crests, sails along their backs to attract mates.



London: Just like brightly plumed peacocks, dinosaurs evolved fancy head crests and sails along their backs to attract mates, says a new study.

Palaeontologists claim that pteranodon crests and eupelycosaur sails are among the earliest and most extreme examples of elaborate sexual signals in the evolution of terrestrial vertebrates.

An international team, led by Dr Joseph Tomkins of Hull University, believes 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 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.”

"Furthermore, small ancestral, sail-backed pelycosaurs would have been too small to need adaptations to thermoregulation," the palaentologists said.

They 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. Indeed the sail of dimetrodon is one of the largest secondary sexual traits of any animal," Dr Tomkins said.

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.

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

The findings have been published in `The American Naturalist` journal.

PTI

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