LONDON (AFP) — A duck-billed dinosaur which was a favourite prey of the Tyrannosaurus Rex grew "like crazy" from egg to adult-size to avoid being eaten by the king of the dino world, a study revealed Wednesday.
The Hypacrosaurus grew three to five times faster than any of its predators including the T-Rex -- and also had babies at a much younger age, expanding its numbers to give it an evolutionary edge.
"By the time the duck-billed dinosaur was fully grown, the tyrannosaurs were only half grown -- it was a huge size difference," said US researcher Drew Lee in an online journal, calling it the "gazelle of the Late Cretaceous."
When full-sized the plant-eating dinosaur, which lived between 67 million and 80 million years ago, was as big as the T-Rex at 30 feet (9.14 metres) tall, but lacked horns or armour to defend itself.
So it gave itself an better evolutionary chance by growing fantastically quickly -- from infancy to adulthood in 10-12 years, compared to up 20-30 years for the T-Rex.
"We were shocked at how fast they grew," said Lisa Cooper, a doctoral student at Kent State University in Ohio, citing evidence from thin sections of its leg bones, which have rings like trees showing the age in terms of years.
"If you look at a cross section of the bone of a nestling or even from within the egg, there are huge spaces in which blood supply was going through the bone, which means they were growing like crazy," she added.
The Hypacrosaurus also reproduced earlier, reaching sexual maturity at only two or three years of age.
"That's another added bonus when facing predators -- if you can keep reproducing, you're set, it's the stuff of evolution," said Cooper.
The research was published in the online journal Proceedings of the Royal Society of London B: Biological Sciences.
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