Description and Classification

Anasazisaurus was a large, plant-eating dinosaur, likely capable of walking on both two legs (bipedally) and four legs (quadrupedally), similar to other hadrosaurs like Edmontosaurus. Scientists estimate it might have reached lengths of around 7.5 meters (25 feet), although this is based on comparisons with more completely known relatives, as only a partial skull of Anasazisaurus has been found.

This dinosaur belongs to the family Hadrosauridae, a diverse group known for their distinctive duck-like bills and complex dental batteries for grinding tough vegetation. More specifically, Anasazisaurus is classified within the subfamily Saurolophinae and the tribe Kritosaurini. This makes it a close relative of other North American hadrosaurs such as Kritosaurus and Naashoibitosaurus, and it shares similarities with Gryposaurus. The exact relationship between these kritosaurins is still studied by paleontologists.

Distinguishing Features

Anasazisaurus is identified by several features of its skull, though our understanding is limited by the incomplete fossils:

• It possessed a short, solid, tab-like crest made of bone that projected backward from the top of its snout, located just above and between its eyes. This crest is different from the long, hollow crests of hadrosaurs like Parasaurolophus or the more prominent nasal humps seen in some other related dinosaurs.
• As a kritosaurin, it would have had a broad, duck-like bill, ideal for stripping leaves from branches or cropping low-growing plants.
• It likely had complex dental batteries, with hundreds of teeth packed together, forming a large grinding surface to process tough plant food.

Paleoenvironment and Diet

Anasazisaurus lived about 74 million years ago in what is now the Kirtland Formation in northwestern New Mexico. During the Late Cretaceous, this area was a warm, humid coastal plain with extensive river systems, floodplains, swamps, and forests. It was located near the western shore of the Western Interior Seaway, an ancient sea that once divided North America.

This environment supported a rich variety of life. Anasazisaurus shared its habitat with other dinosaurs, including the horned dinosaur Pentaceratops, other hadrosaurs such as Parasaurolophus cyrtocristatus, large carnivores like the tyrannosaurid Bistahieversor, armored ankylosaurs, and various smaller animals. As a hadrosaur, Anasazisaurus was a herbivore. Its diet would have consisted of the plants available in its environment, such as conifers, ferns, cycads, and early flowering plants. Its specialized bill and teeth were well-suited for consuming large quantities of this vegetation.

Significance and Ongoing Research

The discovery of Anasazisaurus adds to our knowledge of the diversity of hadrosaur dinosaurs that roamed North America during the Late Cretaceous period. It is particularly important for understanding the evolution and relationships within the Kritosaurini group, which includes several similar-looking duck-billed dinosaurs. The distinctive, short nasal crest of Anasazisaurus helps differentiate it from its close relatives like Kritosaurus and Gryposaurus, though the exact nature and function of this crest are still topics of study.

Ongoing research often involves re-examining the known fossil material and comparing it with new discoveries of related hadrosaurs. Some paleontologists have debated whether Anasazisaurus is truly a distinct genus or if it might represent a species of Kritosaurus. More complete fossil finds would be invaluable in resolving these questions and providing a clearer picture of this dinosaur’s anatomy, behavior, and place in its ancient ecosystem. Studying Anasazisaurus helps scientists piece together the complex web of life in the American Southwest during the final chapters of the age of dinosaurs.