Taxonomic Status of Some Mice of The Peromyscus boylii Group in Eastern Mexico, With Description of a New Subspecies

Saussure (1860) described Peromyscus aztecus from southern México. Osgood (1909) by comparison of one of Saussure's specimens with some from Mirador, Veracruz, concluded that aztecus was a subspecies of P. boylii . Dalquest (1953) incorrectly reported specimens of P. boylii from San Luis Potosí as P. b. aztecus . Merriam (1898) named Peromyscus levipes from Mt. Malinche, Tlaxcala. Thomas (1903) described from Orizaba, Veracruz, P. beatae , which Osgood (1909) mistakenly thought was indistinguishable from P. boylii levipes . Therefore, Osgood in 1909 in his revision of the genus Peromyscus reported only two subspecies of P. boylii from eastern México: P. b. levipes , and P. b. aztecus . Study of Osgood's and Thomas' material, along with recently collected specimens from the states of eastern México, leads me to conclude that P. aztecus and P. boylii are different species; that P. beatae is a valid subspecies different from P. b. levipes ; and finally that specimens of P. boylii from Nuevo León and northwestern Tamaulipas pertain to an hitherto unnamed subspecies.
Peromyscus aztecus Saussure
1909. Peromyscus boylei aztecus , Osgood, N. Amer. Fauna, 28:156, April 17.
Geographic distribution. —Known only from Mirador and Jalapa in Veracruz, and Huachinango in Puebla.
Diagnosis. —Size medium for the genus (see measurements); tail about as long as head and body; dorsal coloration near Sayal Brown (capitalized color terms after Ridgway, 1912); sides reddish; underparts Light Buff; tail bicolored but not distinctly so; supraorbital border of skull angular, and bullae pointed anteriorly; anterior half of braincase nearly straight (not rounded) as viewed from above; upper molar series long (4.7-5.0); incisive foramina short in relation to length of skull.
Comparisons. —From Peromyscus boylii , P. aztecus differs as follows: Larger in most parts measured; maxillary tooth-row 4.7-5.0 instead of 4.0-4.6; color brighter on sides (reddish instead of ochraceous); supraorbital border angular instead of rounded; anterior border of zygomatic plate convex in upper half and almost straight in lower half as opposed to nearly straight throughout in boylii ; pterygoid fossa broader; bullae more pointed anteriorly and less inflated; mesostyles of upper molars larger; surface between orbital region and nasals convex in lateral view instead of flat.