The Southern Pygmy Mouse (Baiomys musculus) 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...

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It is found in El Salvador

El Salvador

El Salvador or simply Salvador is the smallest and the most densely populated country in Central America. The country's capital city and largest city is San Salvador; Santa Ana and San Miguel are also important cultural and commercial centers in the country and in all of Central America...

, Guatemala

Guatemala

Guatemala is a country in Central America bordered by Mexico to the north and west, the Pacific Ocean to the southwest, Belize to the northeast, the Caribbean to the east, and Honduras and El Salvador to the southeast...

, Honduras

Honduras

Honduras is a republic in Central America. It was previously known as Spanish Honduras to differentiate it from British Honduras, which became the modern-day state of Belize...

, Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

, and Nicaragua

Nicaragua

Nicaragua is the largest country in the Central American American isthmus, bordered by Honduras to the north and Costa Rica to the south. The country is situated between 11 and 14 degrees north of the Equator in the Northern Hemisphere, which places it entirely within the tropics. The Pacific Ocean...

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Synonyms:

Baiomys brunneus (J. A. Allen and Chapman, 1897)
Baiomys grisescens Goldman, 1932
Baiomys handleyi Packard, 1958
Baiomys infernatis Hooper, 1952
Baiomys nebulosus Goodwin, 1959
Baiomys nigrescens (Osgood, 1904)
Baiomys pallidus Russell, 1952
Baiomys pullus Packard, 1958