Theropods with ornamented head tend to grow faster than their relatives without bony structures
Scientists have found an unusual explanation for why some dinosaurs used to have enormous bodies.
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Theropods like T. rexes, Allosaurus and Giganotosaurus were among the largest dinosaurs to walk on Earth and they all had a tendency to grow big fairly fast. Now, researchers from North Carolina State University have found that their ‘decorated’ heads were likely the reason behind their rapid growth. Theropod dinosaur species that had bony crests, horns and knobs evolved into giant dinosaurs 20 times faster than those without ornamented skulls.
"We were surprised to find such a strong relationship between ornaments and huge body size in theropods. Something about their world clearly favored bling and big bods." Terry Gates from NC State's Department of Biological Sciences and research said in a statement.
Paleontologists have long believed that dinosaurs use their headgear either to defend themselves from other animals or to attract opposite sex but their role in the growth of dinosaurs was previously unknown.
When researchers looked at different species of theropods, they realized that small theropods like Velociraptor, Ornithomimus and Falcarius did not have any bony structures on their head. Only large theropod species including T. rex and Allosaurus had ornamented heads and these strange structures might have something to do with their huge size.
“For the first time, we're starting to recognize that signaling structures in theropod dinosaurs played a major role in shaping their evolution.” Gates told Live Science.
Observational data and computer modeling allowed researchers to determine when structures like horns, knobs and bony bumps come into play and affect of size of dinosaurs. Researchers found that theropods weighing under 36 kg (about 80 pounds) lacked skull ornaments. Above that threshold, most theropods had ornamentation and once they had developed those bony structures, they would grow enormously every 4 to 6 million years. Other small theropods used to take much longer time to increase their size.
However, it is unclear whether the bony structures are directly responsible for the growth of large theropods or were just contributing to the growth alongside another major factor.