How Ornamented Skulls are Linked to Theropod Dinosaurs' Rapid Growth

A new study from North Carolina State University reveals how crests, horns and knobs found on the skull of theropod dinosaurs are connected to the animals fast growth compared to other species without ornamented skulls.

The study, published in the journal Nature Communications, says that the Tyrannosaurus rex and its cousins grew 20 times faster than other dinosaur species without head embellishments.

Researchers hypothesized that the embellishments on the theropods, such as bumps and crest on their heads, is used for socio-sexual display. It is a way of communication between dinosaurs to mate or defend their territory.

To discover the relationship between these embellishments and the dinosaurs' size, the researchers analyzed 111 fossils of theropods with or without ornaments and compared their sizes over time. Results showed that 20 of the 22 largest theropods had embellishments on their head. Meanwhile, at the end of the spectrum, dinosaurs without a head display usually weighs below 36 kilograms. For example, a theropod species called Acrocanthosaurus did not have head decoration and experienced a slower growth than its larger peers.

"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," said Terry Gates, lecturer in NC State's Department of Biological Sciences and research adjunct at the North Carolina Museum of Natural Sciences, via Science Daily.

Gates and colleague Lindsay Zanno also looked at fossils of Velociraptor, Ornithomimus and Falcarius. These three species are where birds originated. They weigh over 36 kilograms but opted not to have headgears, and instead, used feathers for visual communication.

"Our work supports the idea that vaned feathers were great communication tools from the get-go and may have helped large bird-like theropods sidestep the bother of skeletal bells and whistles, said Zanno.