Fig. 5. Bacula of Neotoma. All × 4.
A, Neotoma angustipalata (topotype, 37062).
B, Neotoma micropus micropus (4 mi. SW Nuevo Laredo, 89147).
C, Neotoma micropus littoralis (Sierra de Tamaulipas, 2 mi. S, 10 mi. W Piedra, 56957).
The known distributions of N. micropus and N. angustapalata do not overlap (neither does the distribution of N. albigula overlap with either in Tamaulipas). The four specimens of N. micropus having the deep re-entrant angle in M1 are from localities near where the ranges of angustapalata and micropus probably meet. This could be interpreted in two ways: (1) these four specimens can be regarded as intergrades between angustapalata and micropus, in which case the former species should be placed as a subspecies of the latter. Or the four specimens, which were collected along with other specimens that lack deep re-entrant angles in the M1, can be assigned, on the basis of the deep angle, to angustapalata, in which case the species micropus and angustapalata would be in part sympatric. Until more material from critical areas is available for study, I continue to recognize angustapalata as a monotypic species. I agree with Hooper that it is closely related to N. micropus.
Measurements.—A female (58865) from 8 km. west and 10 km. north of El Encino, measured as follows: 404; 198; 41; 32; greatest length of skull, 49.7; basilar length, 40.8; zygomatic breadth, 25.9; length of nasals, 18.8; length of incisive foramina, 10.8; length of maxillary tooth-row, 9.9; greatest breadth of interpterygoid space, 4.0.
Records of occurrence.—Specimens examined, 3: 8 km. W, 10 km. N El Encino, 400 ft., 1; type locality, 2.
Neotoma micropus
Southern Plains Wood Rat
Most of the specimens examined were trapped in brushy areas. On the Sierra de Tamaulipas, wood rats were caught in steel traps set near or between rocks. In the vicinity of La Pesca, specimens were trapped on the beach where Spermophilus spilosoma and Sigmodon hispidus were taken also.
Two females, obtained on May 19 and June 10 at Soto la Marina and on the Sierra de Tamaulipas, respectively, each carried 2 embryos that were 40 mm. in crown-rump length. Dice (1937:254) reported that two females collected on July 24 and August 16 on the Sierra San Carlos each carried 2 embryos that ranged from 34 to 36 mm. in crown-rump length.
Neotoma micropus occurs throughout the Tamaulipan Biotic Province and is represented in Tamaulipas by two subspecies, each of which has its type locality in the state. Intergradation between the two takes place at Soto la Marina.