Torosaurus

Torosaurus (meaning "perforated lizard", in reference to the large openings in its frill) is a genus of herbivorous chasmosaurine ceratopsian dinosaur that lived during the late Maastrichtian age of the Late Cretaceous period, between 68 and 66 million years ago, though it is possible that the species range might extend to as far back as 69 million years ago. Fossils have been discovered across the Western Interior of North America, from as far north as Saskatchewan to as far south as Texas.

Measuring between and weighing around , Torosaurus possessed the largest skulls of any known land animal, with the frilled skull reaching in length. Torosaurus is thought to have been the same size as the contemporary Triceratops, but is distinguished by an elongated frill with large oval shaped openings, long squamosal bones of the frill with a trough on their upper surface, and the presence of five or more pairs of hornlets on the back of the frill. Torosaurus also lacked the long nose horn seen in Triceratops prorsus. It instead resembled the earlier and more basal Triceratops horridus, thanks to having a short nose horn. Three species have been named so far: Torosaurus latus, T. gladius, and T. utahensis. T. gladius is no longer considered a valid species, however.