The Texas wolf (Canis lupus monstrabilis), is a possibly subspecies of the gray wolf whose range once included southern and western Texas and northeastern Mexico. It is darker than its more northern cousins, and has a highly arched frontal bone. As of 2005, it is considered a valid subspecies by MSW3, though it is classed as either a synonym of Canis lupus nubilus and Canis lupus baileyi by the United States Fish and Wildlife Service.