How did dinosaurs become so massive? Blame it on their heads. A new research has revealed that the ornamented heads of dinosaurs apparently caused a rapid growth in body mass of these Jurassic creatures.

A team from North Carolina State University examined the body sizes of theropods and how they evolved, revealing lineages of ornamented heads. Thereopods usually have large heads with crests, horns and similar protrusions that have grown faster and larger than their body size.

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Among the 22 theropod species, 20 of them possessed large ornamented heads that manifested bony bumps and crests, and these include the most iconic predators, the Tyrannosaurus Rex and the Allosaurus.

After analyzing a total of 111 ornamented and unadorned theropod species, researchers suggest that head ornamentation triggered this species to evolve into bigger proportions through time as opposed to unornamented species which possessed heads that remained small or regular in size.

According to Terry Gates of North Carolina State University, it was surprising to discover a strong link between ornaments and large body sizes in theropods. This offers a glimpse into the Jurassic period that dinosaurs which are bigger have more favorable chances of survival.

However, this link does not apply to every theropod species. Those that are closely related to modern birds like the Velociraptor, the Falcarius, and the Ornithomimus were all massive. But they did not possess head ornamentation. In this case, feathers replaced skull ornamentation.

Gates added that the new study also suggests that vaned feathers are also communication tools that may have helped larger bird-like theropods not to bother anymore with larger heads.

This new study has been published in the journal Nature Communications.