The researchers looked at 9 triceratops skulls and nine torosaurus skulls, which are far rarer. They discovered that the oldest triceratops skulls showed that thinning in the neck-frill bone where ...

The first, named Triceratops in 1889, had three impressive horns jutting out of its face and a solid, curved frill.

In 2016, one study found that as Triceratops matured, its head frill ballooned in size, suggesting that it became more important later in life —such as during the sexual selection process. Behavior ...

But the researchers say that the triceratops was just a young version of a torosaurus and its horns changed shape as the dinosaur aged. When it reached maturity the holes developed in its neck-frill.