Kritosaurus

Phylogeny: Dinosauria > Ornithischia > Genasauria > Neornithischia > Cerapoda > Ornithopoda > Iguanodontia > Ankylopollexia > Styracosterna > Hadrosauriformes > Hadrosauroidea > Hadrosauridae > Saurolophinae > Kritosaurini

Overview: Hadrosaurids were the most derived of the “duck-billed” dinosaurs. Most of the more popular and widely known “duck-bills” belonged to the family, which was itself split into two main subfamilies – the Lambeosaurinae and the Saurolophinae. Kritosaurus belonged to the latter group. Saurolophines usually lacked the bony head crests seen among lambeosaurines, though this wasn’t always the case. Both lineages were mostly the same in terms of their overall body plan, being sturdily built herbivores that could walk either down on all fours or on their hind legs. Most of their diet was made up of low to mid-level vegetation. Kritosaurus, like all hadrosaurs, possessed both a keratinous beak and rows of tightly-packed, grinding teeth. Hadrosaurs would constantly replace their teeth throughout their lives, growing them rapidly, even as elders. They were able to chew and process their food far more efficiently than any other group of herbivorous dinosaurs.

Saurolophine hadrosaurids are further split into a few major tribes. Kritosaurus is classified within the tribe Kritosaurini, for which it is obviously the namesake. Other notable members of this group includes genera like Gryposaurus and Anasazisaurus. These dinosaurs tended to have prominent, arched nasal bones and large nares (nasal openings). In life, fleshy sacs may’ve encased this structure to act as resonating chambers to make loud calls, or sheathes of keratin formed display structures atop it. Kritosaurus was first described in 1910 by the American paleontologist Barnum Brown (the same man who discovered the holotype specimen of Tyrannosaurus rex). Its name, meaning “separated lizard”, refers to how most of its facial bones were found disarticulated. The earliest reconstruction attempts failed to recognize its nasal arch. Confirmed fossils are known from the southwestern United States and possibly in Mexico. Canadian specimens once referred to it probably belong to the related Gryposaurus, which for a time was seen as the same genus as Kritosaurus.