Coahuilaceratops

Coahuilaceratops (meaning "Coahuila horn face") is a genus of ceratopsian dinosaur. It is a chasmosaurine ceratopsian which lived during the Late Cretaceous period (early Maastrichtian stage) in what is now southern Coahuila in northern Mexico. It is known from the holotype CPC 276, a partial skeleton of an adult individual which includes several skull elements. Another specimen, CPS 277, may represent a juvenile Coahuilaceratops. All specimens of Coahuilaceratops were collected from a single location of the Cerro Huerta Formation, which dates to between 71.5 and 70.5 million years ago. The holotype fossils had originally been believed to come from the underlying Cerro del Pueblo Formation, from the late Campanian.

It was formally described in 2010, though it appeared as an informal designation (nomen nudum) as early as 2008. Coahuilaceratops was named by Mark A. Loewen, Scott D. Sampson, Eric K. Lund, Andrew A. Farke, Martha C. Aguillón Martínez, C.A. de León, R.A. Rodríguez de la Rosa, Michael A. Getty and David A. Eberth in 2010 and the type species is Coahuilaceratops magnacuerna. Although based on incomplete remains, Coahuilaceratops is thought to possess among the largest horns of any dinosaur currently known, rivaling in absolute size those of larger chasmosaurines like Triceratops and Torosaurus. Its horns are estimated to have been up to 1.2 m (4 feet) long. It was a medium-sized ceratopsian, reaching 4 m in length and 1 MT in body mass.

Systematics
Coahuilaceratops is a member of the Chasmosaurinae. Below is a cladogram that represents the findings of Caleb Brown and Donald Henderson (2015), finding Coahuilaceratops to be the sister taxon to the Texan Bravoceratops.

This pairing was replicated by Jordan Mallon et al. in 2016, although Bravoceratops had to be cut from the analysis to create meaningful results. In 2021, Sierraceratops was described and found to clade with Coahuilaceratops and Bravoceratops, and its describers, Sebastian Dalman et al., suggest they all form a clade unique to southern Laramidia.