MEANING: Near crested lizard
PERIOD: Late Cretaceous
CONTINENT: North America
Parasaurolophus is a hadrosaur from the Late Cretaceous known for its large cranial crest. The purpose of this crest is the topic of much debate, with theories including visual recognition of both species and sex, acoustic resonance, and thermoregulation. Parasaurolophus grew to around 9 m in length, and had an estimated weight of somewhere between 3-5 t. Like other hadrosaurs, Parasaurolophus was facultatively bipedal, meaning it was able to walk on two legs or four. It probably preferred to forage for food on four legs, but ran on two.
Parasaurolophus is from the Cretaceous. The Cretaceous is a geological period that lasted from about 145 to 66 million years ago. It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period.
The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct flora and fauna, while dinosaurs continued to dominate on land. The world was ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeared and began to rapidly diversify, becoming the dominant group of plants across the Earth by the end of the Cretaceous, coincident with the decline and extinction of previously widespread gymnosperm groups.
The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary (K–Pg boundary), a geologic signature associated with the mass extinction that lies between the Mesozoic and Cenozoic Eras.
Parasaurolophus is a hadrosaur. Hadrosaurs, casually known as duck-billed dinosaurs, are ornithischian dinosaurs that were common in the Late Cretaceous period. Hadrosaurs were among the most dominant herbivores in Asia and North America, and toward the end of the Cretaceous several lineages dispersed into Europe, Africa, and South America.
Hadrosaurs are known for the flat duck-bill appearance of their snouts. They also had teeth in the back of their mouths that were stacked into complex structures known as dental batteries. Some derived species had large impressive crests on their heads, likely used for sexual display and communication. They were facultative bipeds, meaning they could choose to locomote using only their hind legs, or on all fours, depending on the activity and speed with which they needed to move. The young of some species walked mostly on two legs, and the adults on four.