The Pichincha oldfield mouse (Thomasomys vulcani) is a species of rodent

Rodent

Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....

 in the family Cricetidae

Cricetidae

The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, and New World rats and mice...

. It is present in the Cordillera Occidental of the Andes

Andes

The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...

 of Ecuador

Ecuador

Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...

, where its habitats include shrubby páramo

Páramo

The term páramo can refer to a variety of ecosystems. Some ecologists describe the páramo broadly as “all high, tropical, montane vegetation above the continuous timberline”. A more narrow term classifies the páramo according to its regional placement - specifically located in “the northern Andes...

 and montane forest. It is nocturnal and terrestrial. The specific and common names are references to Pichincha Volcano, on whose slopes the species was discovered at an elevation of 3500 m. The mouse is threatened by conversion of its limited habitat to agricultural use. It has sometimes been considered to be conspecific

Conspecificity

Conspecificity is a concept in biology. Two or more individual organisms, populations, or taxa are conspecific if they belong to the same species....

 with Aepeomys lugens.