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A bighorn sheep, Ovis canadensis, from the late Pleistocene of Mesa del Oro, Cibola County, New Mexico.

In August 1985, the partial skeletal remains of a bighorn sheep were found in Witch Cave (NW1/4, NW1/4, sec. 14, T6N, R5W) on the northern end of Mesa del Oro, Cibola County, New Mexico. Witch Cave is one of many caves of the Pronoun Cave Complex containing late Pleistocene fossil-bearing fill. The mesa consists of early Pleistocene travertine deposits (Jicha, 1956), and most of the caves are partially closed fissures formed by settling of the travertine blocks. Surface openings of the fissures act as pitfall traps and account for the richness of fossil material. The remains of the bighorn sheep were recovered from within the cave on the underside of a clogged fissure approximately 15 meters below the surface and on the cave floor directly beneath it.

The material recovered includes a left partial horn core (Fig. 1), fragments of the right horn core, the complete occipital and right temporal with part of the parietal attached, both M3s, right M2, right M1 and a nearly complete left scapula. The material is deposited in the paleontological collection of the New Mexico Museum of Natural History (NMMNH P-3693).

[FIGURE 1 OMITTED]

Selected skull and tooth measurements of this specimen are compared with those of other late Pleistocene and Holocene Ovis canadensis from the western United States in Table 1. The Witch Cave specimen is larger in all measurements than modern Ovis canadensis measured by Stokes and Condie (1961) and is similar in size to Great Basin Pleistocene bighorn sheep (Stokes and Condie, 1961) except for its generally larger molars (Table 1). Specimens from Dry Cave, New Mexico (Harris and Mundel, 1974), and Littleton, Colorado (Wang and Neas, 1987), have significantly larger horn core measurements than does the Witch Cave bighorn sheep. This may be due, in part, to the young age of the Witch Cave specimen, indicated by the loose sutures between the occipital, parietal, and temporal bones, and completely unworn third upper molars. Based on these comparisons, the Witch Cave bighorn is most likely assignable to Ovis canadensis catclawensis. It falls well within the range of this group and supports the general pattern of Pleistocene bighorn sheep being larger than modern subspecies (Harris and Mundel, 1974).

Although several records of Pleistocene bighorn sheep exist for the Great Basin region, relatively few occurrences are documented for the Southwest. The Witch Cave specimen adds to this growing data base.
TABLE 1. Comparisons of cranial and tooth measurements (mm) for
Pleistocene and Holocene Ovis canadensis. WIC = Witch Cave, New Mexico;
DYC = Dry Cave, New Mexico (Harris and Mundel, 1974); LIT = Littleton,
Colorado (Wang and Neas, 1987); BLF = Bloomfield, New Mexico (Stovall,
1946); GBA = Great Basin (Stokes and Condie, 1961); UTA = modern
specimen from the University of Utah (Stokes and Condie, 1961).

Character WIC DYC LIT BLF GBA UTA

Maximum diameter
at base of horn core 124 139 143 118.5 101-127 120
 (N=12)
Circumference of
horn core at base 349 428 410 346 330-385 335
 (N=12)
Maximum diameter of
occipital condyle 76 76 62.8 55-83 68
 (N=7)
Minimum basioccipital
width 40 35 40 29-33
 (N=5)
Anterior-Posterior
length of M1 20.7 17.5-18 17
 (N=2) (N=1)
Anterior-Posterior
length of M2 24.8 22 21
 (N=2) (N=1)
Anterior-Posterior
length of M3 30 27 28-30 22
 (N=2) (N=1)
Transverse width M1 15 14 13
 (N=2) (N=1)
Transverse width M2 17 14.5-15 14
 (N=2) (N=1)
Transverse width M3 16.5 13.5-14 15
 (N=2) (N=1)


LITERATURE CITED

Harris, A. H., and P. Mundel. 1974. Size reduction in bighorn sheep (Ovis canadensis) at the close of the Pleistocene. J. Mamm., 55:678-680.

Jicha, H. L., Jr. 1956. A deposit of high-calcium lime rock in Valencia County, New Mexico. New Mexico Inst. Mining and Technology and State Bureau of Mines and Mineral Resources Circ. 36:1-32.

Stokes, W. L., and K. C. Condie. 1961. Pleistocene bighorn sheep from the Great Basin. J. Paleontol., 35:598-609.

Wang, X., and J. F. Neas. 1987. A large bighorn sheep Ovis canadensis (Artiodactyla: Bovidae), from the late Pleistocene of Colorado. Southwestern Nat., 32:281-283.

Stovall, J. W. 1946. A Pleistocene Ovis canadensis from New Mexico. J. Paleontol., 20:259-260.

RICHARD A. SMARTT, DAVID J. HAFNER, AND SPENCER G. LUCAS

New Mexico Museum of Natural History, P.O. Box 7010, Albuquerque, New Mexico 87194-7010
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Title Annotation:GENERAL NOTES
Author:Smartt, Richard A.; Hafner, David J.; Lucas, Spencer G.
Publication:The Texas Journal of Science
Geographic Code:1U8NM
Date:Feb 1, 1990
Words:730
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