Kritosaurus (meaning "separated lizard"; sometimes misinterpreted as "noble lizard", in reference to the presumed "Roman nose";[1] the nasal region was fragmented, disarticulated, and originally restored flat) is an incompletely known but historically important genus of extinct hadrosaurid (duckbilled) dinosaur. It lived about 73 million years ago, during the Late Cretaceous of North and possibly South America. Its taxonomic history is convoluted, also incorporating Gryposaurus, Anasazisaurus, and Naashoibitosaurus; this tangle will remain unresolved until better remains of Kritosaurus are described. Despite the dearth of material, this herbivore appeared in dinosaur books until the 1990s, although what was usually represented was the much more completely known Gryposaurus, then thought to be a synonym.
Description[]
Kritosaurus is only definitely determined from a partial skull and lower jaws, and associated undescribed postcranial remains.[2] The greater portion of the muzzle and upper beak are missing, but additional reconstruction in the early 2000s using fragments from the skull that had not been placed before show part of a crest in front of the eyes;[3] the form of the crest is unknown at this point. The length of the skull is estimated at 87 centimeters (34 in) from the tip of the upper beak to the base of the quadrate that articulates with the lower jaw at the back of the skull.[4] Potential diagnostic characteristics of Kritosaurus include a predentary (lower beak) without tooth-like crenulations, a sharp downward bend to the lower jaws near the beak, and a heavy, somewhat rectangular maxilla (upper tooth-bearing bone).[3] If it turns out to be the same as Anasazisaurus or Naashoibitosaurus, then the form of the complete crest is that of a tab or flange beginning in front of the eyes and rising between and above them, but not extended beyond them.
Classification[]
Kritosaurus was a hadrosaurine hadrosaurid, a flat-headed or solid-crested duckbill. Because it is poorly known, its closest relatives are not yet known. Naashoibitosaurus and "K." australis, both of which appear to be very similar, form a clade with Saurolophus in the most recent review of duckbill phylogeny. In the same work, Kritosaurus is confusingly considered both as distinct at the species level and as a dubious name.[2] Location and time separate Kritosaurus and the slightly older, primarily Canadian Gryposaurus, along with some cranial details.