Triceratops

Triceratops is one of the last dinosaurs — it lived right up to the Chicxulub asteroid impact 66 million years ago, sharing its world with Tyrannosaurus rex. The two almost certainly encountered each other, and the evidence is written in bone: Triceratops frills and horns have been found with T-Rex bite marks, and at least one Triceratops hip bone shows healed puncture wounds — meaning it survived a T-Rex attack.

The three horns weren't just for fighting predators. Triceratops horns and frills show an enormous range of variation between individuals, suggesting they were also used for species recognition, dominance displays, and attracting mates — much like antlers in modern deer.

For years, paleontologists debated whether a closely related dinosaur called Torosaurus was actually an adult Triceratops. The frill of Torosaurus has large openings that Triceratops lacks. The current evidence suggests they are indeed separate species, but the debate isn't fully settled.

Triceratops was remarkably common. More Triceratops fossils have been found than any other large Late Cretaceous dinosaur — it may have been the most abundant large herbivore of its time.