A team of international scientists have described a new species of hadrosaur from the end of the Cretaceous. The dinosaur, from Coahuila in northern Mexico has been named Coahuilasaurus lipani. The cranial material used to describe this new duckbill dinosaur was previously identified as Kritosaurus. A closer examination revealed unique autapomorphies of the snout and beak that led to the establishment of this new taxon. Along with other recent dinosaur discoveries from Mexico, Coahuilasaurus shows that Mexico had different species of dinosaurs than the United States and Canada.

Coahuilasaurus lipani life reconstruction. Picture credit: C. Díaz Frías.

Picture credit: C. Díaz Frías

Coahuilasaurus lipani

The new duckbill is known from the front end of a skull. Coahuilasaurus differs from related species in having a very short, deep muzzle and a series of tooth-like projections on the roof of the mouth. The unusual morphology of the jaws suggests a specialisation for the consumption of tough vegetation like palms and cycads.

In recent years, scientists have found a rich fauna of dinosaurs in northern Mexico, like the horned dinosaur (Coahuilaceratops), the crested duckbills Velafrons and Tlatolophus, and now a new kritosaurin hadrosaurid Coahuilasaurus.  Mexico in the Late Cretaceous was very different from today.  It was not an arid, desert environment.  Instead, it was a tropical rainforest full of palm trees and bananas, bordering the Gulf of Mexico.

The Cerro del Pueblo Formation, in Coahuila State, Mexico. Picture credit: Longrich et al.

Picture credit: Longrich et al

An article from 2008 providing information on the discovery of Velafrons coahuilensis: Duckbilled Dinosaur from “South of the Border”.

A blog post from 2010 about the ceratopsian Coahuilaceratops magnacuerna: A New Genus of Horned Dinosaur.

To read a blog post from 2021 about the discovery of Tlatolophus galorum: A New Lambeosaurine from the Gulf of Mexico.

The Different Dinosaur Biotas of Laramidia

Further north, in the USA and Canada, completely different dinosaurs existed. For example, the duckbill Edmontosaurus and the ceratopsian Pachyrhinosaurus. The identification of a new taxon fits the pattern where dinosaurs in the south are distinct from the ones in the northern parts of the ancient landmass of Laramidia.

The dinosaur biota of the Cerro del Pueblo Formation. Picture credit: Longrich et al.

Picture credit: Longrich et al

There are lineages of dinosaurs that disappear from the north but persist for longer in the south. The southern dinosaurs seem to be very different from the northern dinosaurs, so it may be that a lot of what we think we know – including what dinosaur diversity was doing at the very end of the Cretaceous is biased by the fact that until now palaeontologists have been more focused on the dinosaur biota from northern Laramidia.

A drawing of the skull of Coahuilasaurus lipani with known bones show in white (A). A silhouette of C. lipani (B), note the scale bar in (A) of 20 cm and (B) one metre. Picture credit: Longrich et al.

Picture credit: Longrich et al

Commenting on the significance of this new dinosaur discovery Dr Nick Longrich (University of Bath), and a co-author of the study stated:

“Dinosaurs apparently had very small geographic ranges compared to modern mammals, which often range across entire continents. Which is bizarre given that big animals tend to have huge ranges. But what this means is that even in a relatively small area like western North America, you could pack huge numbers of species into a small landmass. Since we’ve only explored a few places for dinosaurs, that implies there’s a huge diversity of dinosaurs waiting to be discovered.”

More Dinosaur Discoveries from Mexico are Likely

Some of those dinosaurs may never be found.  For example, some may never have been preserved as fossils. The remains of others are buried far beneath the ground, or their fossils eroded out millions of years ago and have been weathered away. However, in Coahuila there are vast regions of desert that have hardly been explored.  It is likely that more dinosaur fossils representing new taxa will be discovered in northern Mexico.

The holotype of Coahuilasaurus lipani. The unique morphology of the skull and jaws led to the establishment of a new species of kritosaurin hadrosaurid. Picture credit: Longrich et al.

Picture credit: Longrich et al

Dr Longrich added:

“Canada and the United States have been pretty well-explored at this point. We’ll keep finding new dinosaurs there, but it’s slow going, the low-hanging fruit, the common species we’ve found. Mexico is terra incognita. There’s a lot of dinosaurs waiting to be discovered, we just need to get out there and find them.”

Everything Dinosaur acknowledges the assistance of the Department of Life Sciences (Bath University) and Dr Nicholas Longrich for the compilation of this article.

The scientific paper: “Coahuilasaurus lipani, a New Kritosaurin Hadrosaurid from the Upper Campanian Cerro Del Pueblo Formation, Northern Mexico” by Nicholas R. Longrich, Angel Alejandro Ramirez Velasco, Jim Kirkland, Andrés Eduardo Bermúdez Torres and Claudia Inés Serrano-Brañas published in the journal MDPI Diversity.

The Everything Dinosaur website: Prehistoric Animal Models and Toys.