Gnathovorax cabreirai was a herrerasaurid, a lineage that became extinct not long after the period in which it lived. Credit: illustration: Márcio Castro
Phys.org has an interesting story about dinosaur evolution. Dinosaurs had hollow bones, which made it possible for them to grow as large as they did. A new study published in the journal Scientific Reports looked at three Brazilian specimens from the late Triassic and found they had hollow places in their vertebra similar to later animals like tyrannosaurs and velociraptors. The common ancestor to these early dinosaurs did not have this trait, which leads the researchers to conclude that it evolved independently in each lineage.
Dinosaurs as big as buses or five-story buildings would not be possible if their bones were dense and heavy like ours. Like present-day birds, dinosaurs had hollow bones with inner structures known as air sacs, which made their skeletons lighter and less dense. These structures were apparently so advantageous that they emerged at least three times during the evolution of dinosaurs and pterosaurs (flying reptiles), according to a study described in Scientific Reports.
"Less dense bones containing more air gave the dinosaurs and pterosaurs [and still give birds] more oxygen circulating in their blood, as well as more agility to hunt, flee and fight, or even to fly. They not only used less energy but also kept their bodies cool more efficiently," said Tito Aureliano, first author of the article. The study was part of his Ph.D. research at the State University of Campinas's Institute of Geosciences (IG-UNICAMP).
Aureliano analyzed fossilized bones from three Brazilian species of the Late Triassic (about 233 million years ago), the period in which the dinosaurs emerged. All the bones were found in recent decades in Rio Grande do Sul, Brazil's southernmost state.
