Kritosaurus ‭(‬Seperated lizard‭)

Short Info

Kritosaurus ‭(‬Seperated lizard‭)

Phonetic : Krit-o-sore-us.

Named By : Barnum Brown‭ ‬-‭ ‬1910

Diet : Herbivore

Size : Estimated 8 – 10 meters long

Type of Dinosaur : Euornithopod

Type Species : K.‭ ‬navajovius‭ (‬type‭)

Found in : Argentina, USA‭ ‬-‭ ‬New Mexico‭ ‬-‭ ‬Kirtland Formatio

When it Lived : Late Cretaceous, 78-74 million years ago

Kritosaurus, a genus of hadrosaurid dinosaurs (duck-billed), is not well known. It lived between 74.5 and 66 million years ago in the Late Cretaceous period of North America. Its name is “separated Lizard”, which refers to the arrangement of the cheekbones in an incomplete skull. However, it is sometimes mistranslated as “noble Zander” because of its presumed Roman nose. The original specimen had the nasal region disarticulated and fragmented, but was later restored flat.


Kritosaurus SabinosaurioElias Garcia-Ortiz from Guadalajara, Mexico, CC BY-SA 2.0, via Wikimedia Commons


Barnum Brown, a follow-up to an earlier expedition, discovered the Kritosaurus type specimen (AMNH 5799) in San Juan County, New Mexico. Although he was initially unable to correlate the stratigraphy, he was eventually able to identify it as being from the Kirtland Formation’s late Campanian-age De-na-zin Member. Brown rebuilt the skull’s front after Edmontosaurus. He left many fragments. Brown noticed something different about the fragments and attributed the difference to crushing. He wanted to call it Nectosaurus at first, but he discovered that the name was already in use. Jan Versluys had previously visited Brown and accidentally leaked the name. He retained the exact name and it was changed to K. navajovius.

Brown’s view of the anatomy of his dinosaur’s nose changed after the 1914 publication of the Canadian genus Gryposaurus. He reconstructed the original reconstruction from fragments and gave it a Gryposaurus-like arched nose crest. Charles Gilmore supported his decision to synonymize Gryposaurus and Kritosaurus. This synonymy was used throughout the 1920s (William Parks’s Canadian designation as Kritosaurus incurvimanus). It became standard after Richard Swann Lull’s 1942 monograph about North American hadrosaurids. Between this point and 1990, Kritosaurus would have at least three types species, K. navajovius (K. incurvimanus) and K. notabilis (the former type species Gryposaurus). Lull and Wright also assigned Kritosaurus the poorly-known species Hadrosaurus breviceps (1889), which was discovered from a Montana dentary of the Campanian-age Judith River Formation. However, this has been withdrawn.

Hadrosaurus was a synonym for Kritosaurus, Gryposaurus or both in the late 1970s and 1980s. This was especially true in semi-technical “dinosaur dictionary” discussions. David B. Norman’s The Illustrated Encyclopedia of Dinosaurs uses Kritosaurus as the Canadian material (Gryposaurus), but names the mounted skeleton of K. incurvimanus Hadrosaurus.

Synonymizations of Kritosaurus, Gryposaurus, that occurred between the 1910s and 1990 created a distortion of the original Kritosaurus material. The Canadian material is much better and so most of the representations and discussions about Kritosaurus between the 1920s and 1990 can be applied to Gryposaurus. This includes James Hopson’s discussion of the cranial ornamentation of hadrosaurs and its adaptation for the public in The Illustrated Encyclopedia of Dinosaurs.

Jose Bonaparte, an Argentine paleontologist, and his colleagues named Kritosaurus Australis in 1984 for their hadrosaur bones, which were found in the Los Alamitos Formation, Rio Negro (Patagonia), Argentina. This species is now considered to be a synonym for Secernosaurus koerneri.

Jack Horner and David B. Weishampel again separated Gryposaurus in 1990. They cited the uncertainty that was associated with Gryposaurus’ partial skull. Horner described in 1992 two additional skulls from New Mexico that belonged to Kritosaurus. He also showed that the skull was very different from Gryposaurus. However, Adrian Hunt and Spencer G. Lucas placed each skull in its own genera, creating Anasazisaurus or Naashoibitosaurus.

American paleontologists Spencer G. Lucas and Adrian Hunt named Anasazisaurus Horneri in 1993. Named Anasazisaurus horneri was derived from Anasazi, an ancient Native American tribe, and the Greek word for “lizard”, sauros. Anasazis were known for their rock-dwellings such as the ones found in Chaco Canyon near fossil Anasazisaurus bones. Anaasazi, a Navajo language term meaning “Anasazi”, is the actual name of the species. This species was named after Jack Horner, an American paleontologist who first described it in 1992. The only known specimen, the holotype skull, was collected by a Brigham Young University field team in San Juan County in late 1970s. It is now housed at BYU under BYU 12950.

Horner initially assigned the Anasazisaurus Skull to Kritosaurus nuvajovius. However, Hunt and Lucas couldn’t find any diagnostic features in Kritosaurus’ limited material and declared the genus a nomen dubium. Anasazisaurus skull had diagnostic features on its own and didn’t appear to have any common features with Kritosaurus. It was therefore given the new name Anasazisaurus Horneri. This opinion was also supported by other authors. This is not the case with all authors. Thomas E. Williamson, in particular, defended Horner’s original interpretation. Several subsequent studies also recognized both distinct genera.

Albert PrietoMarquez published a comprehensive analysis of Kritosaurus material in 2013. He confirmed the status of Naashoibitosaurus a distinct genus. However, he found that Kritosaurus type specimens and Anasazisaurus type specimens were not distinguishable when comparing overlapping elements. Only those bones that were found in both specimens. Anasazisaurus was therefore considered a synonym for Kritosaurus by Prieto Marquez, but it is still K. horneri.

Kritosaurus Sp. was described as a partial skeleton taken from the Sabinas basin in Mexico. Jim Kirkland and his colleagues called it Kritosaurus sp. However, Prieto Marquez (2013) considered it an indeterminate saurolophine. This skeleton, which is approximately 20% larger than any other specimens, measures around 11 meters [36 feet] in length and has a distinctively curving ischium. It is the largest well-documented North American saurolophine skeleton. The skull material also contains missing nasal bones.

One possible second, but valid Kritosaurus species may have lived in Javelina Formation with Kritosaurus nuvajovius.

Source: Wikipedia