Sciurus hypopyrrhus (subspecies of and may be synonymous with Sciurus aureogaster) - Mexican Red-Bellied Squirrel
This subspecies of the Mexican Gray Squirrel is possibly just a variation on Sciurus aureogaster. As it has no distinct population separate from the Mexican Gray, the Red-Bellied and melanistic “subspecies” (all of which interbreed) are often considered nothing more than color variants.
Biologia centralia-americana. Edward Richard Alston, 1882.