MEANING: Coahuila lizard
PERIOD: Late Cretaceous
CONTINENT: North America
Coahuilasaurus is a large saurolophine hadrosaur that lived about 72 million years ago in the Late Cretaceous of what is now Mexico. Large Hadrosaurs were very common in the northern hemisphere during the Late Cretaceous, and made up the bulk of herbivorous fauna, apparently replacing sauropods which were found almost exclusively in the southern hemisphere at this time. Coahuilasaurus is a kritosaurin, which are known for the large arched nasal formations above their beaks.
Abstract from paper: The Late Cretaceous of Western North America (Laramidia) supported a diverse dinosaur fauna, with duckbilled dinosaurs (Hadrosauridae) being among the most speciose and abundant members of this assemblage. Historically, collecting and preservational biases have meant that dinosaurs from Mexico and the American Southwest are poorly known compared to those of the northern Great Plains. However, evidence increasingly suggests that distinct species and clades inhabited southern Laramidia. Here, a new kritosaurin hadrosaurid, represented by the anterior part of a skull, is reported from the late Campanian of the Cerro del Pueblo Formation, ~72.5 Ma, in Coahuila, Mexico. The Cerro del Pueblo Formation kritosaur was originally considered to represent the same species as a saurolophine from the Olmos Formation of Sabinas, but the Sabinas hadrosaur is now considered a distinct taxon. More recently, the Cerro del Pueblo Formation kritosaur has been referred to Kritosaurus navajovius. We show it represents a new species related to Gryposaurus. The new species is distinguished by its large size, the shape of the premaxillary nasal process, the strongly downturned dentary, and massive denticles on the premaxilla’s palatal surface, supporting recognition of a new taxon, Coahuilasaurus lipani. The dinosaur assemblage of the Cerro del Pueblo Formation shows higher diversity than the contemporaneous fauna of the Horseshoe Canyon Formation in Alberta. Furthermore, Kritosaurini, Lambeosaurini, and Parasaurolophini all persist into the latest Campanian in southern Laramidia after disappearing from northern Laramidia. These patterns suggest declining herbivore diversity seen at high latitudes may be a local, rather than global phenomenon, perhaps driven by cooling at high latitudes in the Late Campanian and Maastrichtian.
Coahuilasaurus 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.
Coahuilasaurus 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.