Researchers Learn More About Sex Lives of Dinosaurs

A new study offers the most intriguing clue yet for determining the sex of certain dinosaurs: injuries that may have resulted from mating. For decades, paleontologists have struggled to tell male from female dinosaurs based on fossils alone, but the latest research focuses on a pattern of healed injuries in hadrosaurs, herbivores of the Late Cretaceous also known as duck-billed dinosaurs. These breaks, found consistently on the vertebrae past the base of the tail, are thought to have resulted from males mounting females and inadvertently damaging their spines during mating, CNN reports.

The study, published in the journal iScience, analyzed nearly 500 hadrosaur tail vertebrae from museum collections across North America, Europe, and eastern Russia. The researchers used simulations to rule out alternative causes, like fighting, accidents, or everyday movement. They noted that the injuries were widespread and appeared in multiple species of duck-billed dinosaurs. They determined that the injuries were nonfatal because there were signs of healing and sometimes evidence of a second injury, suggesting repeated behavior, RTE reports.

"If the mating hypothesis is correct, we can infer that an individual with the injuries is female, said lead study author Dr. Filippo Bertozzo. "This will be a game changer since it will enable other questions to be answered about differences between male and female dinosaurs," Bertozzo said. He plans to investigate whether similar injuries can be found in other dinosaur species. Bertozzo notes that the find has a "cascade of implications" and that it's possible the differences between male and female dinosaurs may have led to them being declared different species.

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"The story is just at the beginning, and I hope ours is only one of the initial steps to better understand this aspect of the life of dinosaurs," Bertozzo said. Other researchers say the findings are promising but not definitive. They praised the creativity of Bertozzo and his team. "It's exciting to think that even the scars of these ancient creatures can reveal moments of their most intimate lives, quite literally, the 'love life' of dinosaurs written in their bones," Yoshitsugu Kobayashi, a professor of vertebrate paleontology at Hokkaido University Museum, tells CNN.