Five females taken on October 18 at Nicolás carried embryos (one to two per female), which averaged 22.2 (11-45) mm. in crown-rump length. Another female, taken nine miles southwest of Tula on October 13, carried 2 embryos that were 35 mm. in crown-rump length. The average weight of the five pregnant females was 196.7 (183-207) grams. The average weights of nine adult males and six non-pregnant females from Miquihuana were, respectively, 215.6 (175-250) and 162.5 (155-175) grams.
Records of occurrence.—Specimens examined, 51: Miquihuana, 6400 ft., 22; Joya Verde, 35 km. SW Cd. Victoria (on Jaumave Road) 3800 ft., 2; Nicolás, 56 km. NW Tula, 5500 ft., 10; Tajada, 23 mi. NW Tula, 5200 ft, 2; 9 mi. SW Tula, 3900 ft., 15.
Additional record: Jaumave (Goldman, 1910:37).
Neotoma angustapalata Baker
Tamaulipas Wood Rat
1951. Neotoma angustapalata Baker, Univ. Kansas Publ., Mus. Nat. Hist., 5:217, December 15, type from 70 km. by highway S Ciudad Victoria, and 6 km. W Pan-American highway at El Carrizo, Tamaulipas.
Distribution in Tamaulipas.—Southern part of state; presently known from two localities.
Baker (1951:218) reported that specimens from the type locality were taken in crevices among rocks on a small hillside that supported a sparse cover of vegetation growing from a deep layer of humus. The specimen from eight kilometers west and 10 kilometers north of El Encino was shot about 40 yards from the entrance to a large cave, but no sign of wood rats were found there. Hooper (1953:9) reported that N. angustapalata occupied caves at Rancho del Cielo, where a female with two nursing young was taken.
When Baker (op. cit.) described Neotoma angustapalata on the basis of two specimens from El Carrizo, he assigned the species to the N. mexicana group because of the deep anterointernal re-entrant angle of M1. The deep angle found in N. mexicana differs markedly from the typical condition in either N. micropus or N. albigula. Study of the cranial characters and bacula of specimens of N. micropus and N. angustapalata tends to corroborate the statement of Hooper (1953:10), who commented on the taxonomic relationships of N. angustapalata as follows: "It should be pointed out that all characters considered ... the specimens [angustapalata] appear to be large, deeply pigmented examples of the species N. micropus notwithstanding the deep anterior fold in M1. The presence of that deep fold is far from an absolute character in the mexicanus [sic] group."
My study of 48 crania of N. micropus from Tamaulipas reveals that the depth of the re-entrant angle of M1 is extremely variable, from almost absent in some individuals to deep (as in angustapalata) in others. Four specimens, one (56958) from the Sierra de Tamaulipas and three (56960, 56965, 56966) from the vicinity of Altamira, have the re-entrant angle as deep as in the holotype and topotype of angustapalata.
Comparison of the bacula of the holotype and one topotype of angustapalata with 15 bacula of N. micropus reveal that on the average the baculum of angustapalata differs from that of micropus in being longer, and narrower at the base (greatest length, 7.1, width at base, 3.4 mm., in the topotype). One specimen of N. micropus littoralis from the vicinity of Altamira, however, has a baculum of the same shape as in angustapalata (this same specimen is one of the three from there in which the re-entrant angle of the M1 is deep). The shape of the baculum among specimens of micropus is highly variable and bacula of specimens from different localities frequently are slightly different (see [Fig. 5]).