Order Rodentia - Family Cricetidae Author Wilson, Don E. Author Reeder, DeeAnn text 2005 The Johns Hopkins University Press Baltimore Mammal Species of the World: a Taxonomic and Geographic Reference (3 rd Edition), Volume 2 955 1189 book chapter 0-8018-8221-4 10.5281/zenodo.7316535 Isthmomys Hooper and Musser 1964 Isthmomys Hooper and Musser 1964 , Occas. Pap. Mus . Zool., Univ. Michigan , 635: 12 . Type Species: Megadontomys flavidus Bangs 1902 Species and subspecies: 2 species: Species Isthmomys flavidus ( Bangs 1902 ) Species Isthmomys pirrensis (Goldman 1912) Discussion: Reithrodontomyini. Species associated here were originally classified in Megadontomys , used either as a genus or as a subgenus of Peromyscus ( Osgood, 1909 ) . Isthmomys was later diagnosed as a subgenus of Peromyscus ( Hooper and Musser, 1964b ) and maintained at this rank by Hooper (1968); diagnosis emended and accorded generic status by Carleton (1980 , 1989). Sister-group relationship with Megadontomys proposed by Carleton (1980) but unsupported by chromosomal banding data ( Stangl and Baker, 1984b ). Aspects of morphology considered by Carleton (1973 , 1980 ), Hooper and Musser (1964b) , and Linzey and Layne (1969 , 1974 ); karyology by Stangl and Baker (1984b) .