Torosaurus (“perforated lizard”) was a particularly widespread member of the Triceratopsini, found across western North America. Fossils are known from Canada all the way down to New Mexico and Texas in the southern regions of the USA, although the southernmost specimens represent a second species within the genus, T. utahensis.
Living about 68-66 million years ago, it was one of the largest ceratopsids, reaching body lengths of around 7.5m (24’7″). The size and shape of its three horns varied between individuals, from short and straight to much longer and curving forwards.
It had one of the longest skulls of any known land animal, with some specimens’ heads measuring at least 2.5m long (8′2″). Around half of that length consisted solely of its frill, the shape of which was also quite variable – some were very flat while others curved upwards, and the top edge could be either rounded, straight, or have a “heart-shaped” notch.
In 2010 a study was published by John Scannella and Jack Horner, hypothesizing that Torosaurus wasn’t a unique genus and was actually the fully mature form of Triceratops. While poor media reporting briefly sent the internet into a panic about Triceratops “never existing”, further studies by other paleontologists have failed to come up with the same results, and the debate doesn’t seem to have come to any overall consensus yet.