Oryzomys is a genus of semiaquatic rodents in the tribe Oryzomyini living in southern North America and far northern South America.
From the en.wikipedia.org
Oryzomys peninsulae is a medium-sized member of the genus, smaller than O. albiventer but larger than O. couesi mexicanus.
From the en.wikipedia.org
Oryzomys couesi and at least six more narrowly distributed species with peripheral distributions together form the O. couesi group within the genus Oryzomys.