Iguanacolossus, a dinosaur from the Early Cretaceous era was discovered in 1998 in the Yellow Cat Member of the Cedar Mountain Formation, located in eastern Utah, USA. Its name, "Iguanacolossus," is a nod to its presumed relationship with iguanodontian dinosaurs and its impressive size. Iguanacolossus is classified within the group Iguanodontia, specifically the subfamily Hadrosauridae.

Iguanacolossus was a large dinosaur, measuring around 30 feet (9 meters) in length and weighing several tons. It belonged to the hadrosaurids, a group of herbivorous dinosaurs characterized by their duck-bill-like mouths and elaborate head crests. Iguanacolossus likely possessed a similar cranial crest, although the exact shape and size remain subjects of scientific investigation.

Its robust hind limbs and relatively shorter forelimbs suggest that Iguanacolossus was a quadrupedal dinosaur, using both its hind legs and forelimbs to move through its environment. Its broad mouth was filled with hundreds of tightly packed teeth, which were well-suited for processing plant material.

Iguanacolossus was well-adapted to its herbivorous lifestyle, using its beak and dental batteries to efficiently consume vegetation. The presence of gastroliths (gizzard stones) in some fossils suggests that it may have employed a gizzard-based digestive system to aid in breaking down tough plant material. Its diet likely consisted of a variety of plants, including ferns, cycads, and conifers, which were abundant during the Early Cretaceous period.

Behaviorally, Iguanacolossus was likely a social creature that lived in herds. This social structure would have provided protection against predators and facilitated more efficient foraging. The presence of bonebeds, where multiple individuals are found together, supports the idea of herd behavior.