The quaternary paleontology and paleoecology of crystal ball cave, millard county, utah: with emphasis on the mammals and the description of a new species of fossil skunk

S. nuttallii presently inhabits the region of the cave and northward, whereas S. audubonii inhabits the region of the cave and southward. S. nuttallii also tends to occur at higher elevations and in more wooded or bushy areas than S. audubonii, which lives in plains or open country (Hall 1951). Since Gandy Mountain is presently covered with only sparse bushes and is surrounded by open plains, the presence of S. nuttallii and absence of S. audubonii suggests the replacement of woodland-alpine vegetation by the present desert conditions since the Pleistocene.

Lepus cf. americanus

Material--Right dentary with I/1, P/3,/4, M/1,/2 (BYUVP 5519), anterior portion of left dentary with P/4, M/1 (BYUVP 5543). A left dentary with /I (BYUVP 5430) falls within the size range of L. americanus and L. californicus.

Discussion--The jaw dimensions and P/3 widths of these specimens are intermediate in size between the Sylvilagus specimens (described above) and the majority of the Lepus specimens (described below). They fall in and near the range of variation of the smallest L. californicus and largest S. audubonii specimens (see figure 4), but most of the P/3's of these two species have a highly crenulated second reentrant angle whereas the P/3 of BYUVP 5519 does not. These specimens are also indistinguishable from S. floridanus, but this species has never been reported living or as a fossil from Utah or Nevada.

L. americanus does not presently occur in the Snake Range but does occur 100 miles (160 km) to the north and east, mainly at high elevations (Durrant 1952, Hall 1951). Since the assemblage generally contains more species that presently range north of the cave than south of the cave, it is not at all unreasonable that L. americanus could have inhabited the region of the cave in the recent geologic past. Kurten and Anderson (1980) listed a number of fossil sites where L. americanus has been found south of its present range.

Lepus townsendii

Material--Fused dentary pair with right P/3,/4, M/1,/2,/3, left I/, P/3,/4, M/1,/2 (BYUVP 5488), right dentary with M/1,/2 (BYUVP 5467), right dentary with I (BYUVP 5533), left dentary with all teeth (BYUVP 5442), left dentary with I, P/3,/4, M/1,/2 (BYUVP 5484), 5 left dentaries without teeth (BYUVP 5424, 5429, 5474, 5532, LACM 123657), anterior portion of left dentary without teeth (BYUVP 5439), 7 isolated right P/3's (BYUVP 5733, 5770-5772, 5793, 5796, 5802), 7 isolated left P/3's (BYUVP 5735, 5736, 5780, 5783, 5790, 5791, 5804). A partial left dentary with P/3 (BYUVP 5485), 28 dentaries lacking P/3 (BYUVP 5422, 5427, 5436, 5438, 5448, 5450, 5454, 5456, 5458, 5462, 5473, 5475, 5478, 5483, 5487, 5489, 5493, 5495, 5500-5502, 5524, 5527, 5530, 5531, 5540-5542), 7 isolated right P/3's (BYUVP 5617, 5732, 5745, 5768, 5774, 5778, 5792), and 5 isolated left P/3's (BYUVP 5716, 5775, 5776, 5801, 5809) show characteristics common to both L. townsendii and L. californicus.

Discussion--L. townsendii and L. californicus are distinguished from Sylvilagus and L. americanus by their large size. They are distinguished from each other by L. townsendii having a larger mean size (see figure 4) and having less crenulation in the second reentrant angle of P/3 than L. californicus (Hibbard 1952). Miller (1976) observed L. californicus to have a highly crenulated P/3 in most, but not all, cases, and Hibbard (1944, 1963) noted that individual variation is very great. My observations and those of J. A. White (1984 personal communication) show that many individuals of these species cannot be distinguished by either size or the amount of crenulation in P/3. But statistical analysis can be used to estimate their relative abundance (Grayson 1977). Hibbard (1952) stated that the anterior part of P/3 is narrower in L. townsendii than in L. californicus, but although I noticed variation in the narrowness and roundedness of the anterior P/3's, it did not correlate with the amount of crenulation in the second reentrant angle of that tooth. BYUVP 5424, 5467, and 5474 have greater alveolar length (P/3-M/3) to diastema length ratios than any Recent leporid specimens measured (see figure 4), but they fall closest in size, especially based on their long tooth row length, to L. townsendii.

Since 11 of the 43 measurable Lepus dentaries are larger than any modern L. californicus specimens measured (see figure 4) and over half of the large Lepus P/3's from the assemblage show no crenulation (a very rare condition in L. californicus), it is clear that L. townsendii is well represented. Most of the 29 jaws that could be either L. townsendii or L. californicus are closer to the mean size of L. townsendii, and the isolated 13 P/3's of L. townsendii or L. californicus have slight crenulation in the second reentrant angle yet are considerably less crenulated than the vast majority of L. californicus specimens. Since only two highly crenulated P/3's clearly belonging to L. californicus (listed below) were found, most of these 13 P/3's with intermediate crenulation probably belong to L. townsendii. Based on this information I estimate that the ratio of L. townsendii to L. californicus specimens from the Crystal Ball Cave assemblage is about ten to one.

Grayson (1977) stated that L. townsendii is a more northern species and inhabits higher elevations and more grassy habitats than L. californicus, which prefers dryer shrubby areas. With Sylvilagus, the more northern species is represented in the assemblage while the more southern species is not. This is also the trend with Lepus. Hall (1981) reported L. townsendii in the area of Crystal Ball Cave but Durrant (1952), in a more detailed map, did not. Both report L. californicus throughout the Bonneville Basin area. I have seen numerous L. californicus around Gandy but never a L. townsendii, and J. C. Bates (1984 personal communication) reported never noticing any L. townsendii but numerous L. californicus. This difference between the fossil and living species at Gandy suggests that climatic boundaries have shifted upward in latitude and elevation since the Pleistocene. Grayson (1977), using both fossil and Recent data, demonstrated that L. californicus increased in number at the expense of L. townsendii during the Recent, and that it became the more dominant species in the Great Basin 5,000 to 7,000 years ago. Although the ecological and adaptational differences between these two species are not fully understood, Grayson (1977) attributed this change to a post-Pleistocene warming trend. The species shift indicated by the Crystal Ball Cave assemblage reiterates the data presented by Grayson (1977).

Lepus californicus

Material--Right P/3 (BYUVP 5781), left P/3 (BYUVP 5734). Twenty-nine dentaries and 13 other P/3's (listed under L. townsendii) show characters found in both L. townsendii and L. californicus. A left dentary with /I (BYUVP 5430) falls within the size range of L. americanus and L. californicus.

Discussion--L. californicus differs from L. townsendii in having a smaller mean size (see figure 4) and a more crenulated second reentrant angle in P/3 as discussed above. The two P/3 specimens listed above have more crenulation than was seen in eight Recent L. townsendii specimens but are typical of L. californicus. The 13 P/3's of either L. townsendii or L. californicus (listed and discussed above) show less crenulation than the vast majority of L. californicus specimens studied, but some of them could represent L. californicus since crenulation in the P/3 is not always present (Miller 1976). L. californicus is presently the most common lagomorph around Crystal Ball Cave (J. C. Bates 1983 personal communication), so its poor representation in the fossil assemblage suggests that it has only recently become abundant there.

Order Rodentia
Family Sciuridae
Marmota flaviventris

Material-Anterior portion of skull with right M1/,2/,3/, left M1/,3/ (BYUVP 6528), anterior portion of skull without teeth (LACM 123663), dentary pair with right M/1,/3 (BYUVP 6536), right dentary with P/4, M/1,/3 (LACM 123665), right dentary with M/1,/2,/3 (BYUVP 6543), right dentary with M/2,/3 (BYUVP 6621), right dentary with M/3 (BYUVP 6620), left dentary with /I, M/1,/2,/3 (BYUVP 6477), left dentary with M/1,/2,/3 (LACM 123669). Another 70 partial maxillae (some with teeth), 70 partial dentaries (some with teeth), and approximately 300 isolated cheek teeth (BYUVP 6476, 6478-6518, 6520-6527, 6529-6535, 6537-6542, 6544-6605, 6607-6619, 6622-6648, LACM 123664, 123666-123668, 123670) are of Marmota and compare favorably with M. flaviventris.

Discussion--Marmota is distinctly larger than other living sciurids (Hall 1981) but distinctly smaller than the extinct Paenemarmota (Repenning 1962). M. flaviventris is distinguished from M. monax by its anteriorly divergent upper tooth rows and from M. caligata, M. olympus, and M. vancouverensis by its smaller size (Hall 1981). M. flaviventris is also distinguished from these other species by its less massive dentition, M3/ being longer than wide, and M/3 having a triangular rather than a quadrangular outline (Logan 1983). Hay (1921) named M. arizonae based on a partial skull from northern Arizona and said it was similar to M. flaviventris. Since the specimen is probably late Pliocene in age and the validity of the species is uncertain (Kurten and Anderson 1980), it is not considered a candidate for the Crystal Ball Cave specimens, all of which are indistinguishable from Recent M. flaviventris.

The presence of M. flaviventris in the Crystal Ball Cave assemblage represents a shift in the climate and vegetation of the area because this species now inhabits only much higher elevations in the Snake Range (Hall 1981, Mead et al. 1982) and does not live on or around Gandy Mountain (J. C. Bates 1983 personal communication). Hall (1946) reported fossil M. flaviventris from several caves far south of this species' present range. Zimina and Gerasimov (1969) proposed that the marmot greatly expanded its distribution and numbers under late Pleistocene periglacial conditions for which it was well adapted but has since diminished significantly. M. flaviventris is not a cave-dwelling species, so its great abundance in the Crystal Ball Cave assemblage suggests that it once lived on Gandy Mountain in large numbers, strongly supporting the hypothesis of Zimina and Gerasimov (1969).

Spermophilus townsendii

Material--Anterior portion of skull with both I/'s (BYUVP 6060), partial skull with right P4/, M1/,2/ (BYUVP 6255), partial skull without teeth (BYUVP 6462), 7 right dentaries with all teeth (BYUVP 6107, 6109, 6141, 6282, 6284, 6326, 7256), and 2 left dentaries with all teeth (BYUVP 6421, 6433). Another 439 partial maxillae (some with teeth), 562 partial dentaries (some with teeth), and approximately 4,000 isolated teeth compare favorably with S. townsendii.

Discussion--Spermophilus townsendii has the smallest mean size of any North American species of Spermophilus and is also slightly smaller than Ammospermophilus leucurus (Hall 1981). Spermophilus also differs from Ammospermophilus by having distinctly larger masseteric tubercles just anterior to the upper tooth rows (Hall 1981). The three partial skulls listed above and many of the partial maxillae without teeth have large masseteric tubercles that distinguish them from Ammospermophilus. All of the specimens listed above compare best in size with S. townsendii, but some of those only referred to this species are probably Ammospermophilus. Kurten and Anderson (1980) listed 13 extinct species of Spermophilus, but the only one close enough in size and age of deposits to the Crystal Ball Cave specimens to be considered is S. taylori, named by Hay (1921) based on a single specimen from Texas. Kurten and Anderson (1980) consider this a doubtful species, and it is most likely a synonym of S. townsendii, so it is not considered here.

The presence of a single species of Spermophilus at Crystal Ball Cave is a striking contrast to the five possible species recovered from Smith Creek Cave in subequal numbers (Mead et al. 1982). These include S. cf. townsendii, S. variegatus, and S. cf. lateralis, which still inhabit the Snake Range, and S. cf. richardsonii and S. cf. beldingi, which have been extirpated but still inhabit Utah and/or Nevada (Hall 1981). The reason for this difference may be that Smith Creek Cave is at the base of 12,050 foot (3,673 meter) Mount Moriah and at the edge of the flat open Snake Valley, an area of diverse niches in contact with several diverse environments even now, and certainly an area across which climatic boundaries crossed many times during the Pleistocene. Gandy Mountain, on the other hand, is only a small hill far out in Snake Valley, the area most favorable to S. townsendii (Hall 1946), and is isolated from the main Snake Range by 6 miles (10 km) of flat valley.

The abundance of Spermophilus townsendii fossils at Crystal Ball Cave suggests that this squirrel lived around Gandy Mountain in large numbers for a long time, probably since fossils started accumulating in the cave. Durrant (1952) said this species is well-suited to the western Utah desert and is particularly abundant around springs. Hall (1946) told how S. townsendii was a traditional food for native American Indians. S. townsendii is not a cave-dwelling animal as is Neotoma, and yet it is over twice as abundant as Neotoma in the assemblage (contrary to my earlier statement that Neotoma was the best represented genus, Heaton 1984). Neotoma has a much more restricted niche than Spermophilus and is never found in large numbers. Since squirrels are very unlikely to venture deep into caves, all the specimens must have been brought in by wood rats and/or small carnivores. It is interesting that fossil deposition occurred so rapidly, even deep in this isolated cave, that an outside species is better represented than the primary cave-dwelling species. J. C. Bates (1984 personal communication) reported seeing no squirrels on Gandy Mountain and only a few in the surrounding valley in the many years he has lived in Gandy. This, in contrast to its abundance as a fossil, suggests that S. townsendii reduced its numbers at the close of the Pleistocene.

Ammospermophilus cf. leucurus

Material--Right maxilla without teeth (BYUVP 8295), 2 left maxillae without teeth (BYUVP 8296, 8297). Some of the 439 maxillae, 562 dentaries, and approximately 4,000 isolated teeth listed under Spermophilus townsendii probably also belong to this taxon.

Discussion--Ammospermophilus is distinguished from Spermophilus by its smaller masseteric tubercle and its less robust lower cheek teeth (Hall 1981). A. leucurus now lives around Gandy Mountain while A. harrisii, A. interpres, A. insularis, and A. nelsoni, the other four extant species, occur only south of Utah (Hall 1981), so the Crystal Ball Cave specimens are referred to A. leucurus although no character could be found to rule the others out.

According to Durrant (1952) A. leucurus commonly occurs with S. townsendii but has a more restricted habitat, preferring rocky terrains. Ammospermophilus is best adapted for high temperatures (Vaughan 1972), and its low abundance in the assemblage compared to Spermophilus townsendii suggests that it has not inhabited the area as long, at least not in its present abundance. With summers becoming hotter and drier at the close of the Pleistocene, Ammospermophilus may have increased its numbers at the expense of other species in Recent times.

Eutamius minimus

Material--Right dentary with P/4, M/1,/2 (BYUVP 6812), 3 right

dentaries with P/4, M/1 (BYUVP 6171, 6210, 6755), left dentary with all teeth (BYUVP 6190).

Discussion--Eutamius has two premolars in each maxilla whereas Tamius has only one. E. minimus is the smallest species of Eutamius and has a narrower and squarer P/4 than E. dorsalis or E. umbrinus. All the specimens listed above match E. minimus with respect to the P/4 and are smaller than the other species. E. minimus and E. dorsalis live in the region of Crystal Ball Cave and E. umbrinus lives higher in the Snake Range and westward into Nevada (Hall 1981). E. minimus was also recovered from Smith Creek Cave (Mead et al. 1982). E. minimus inhabits diverse habitats from deserts to forests, so its presence in the assemblage is not surprising.

Eutamius dorsalis

Material--Right dentary with P/4, M/1,/2,/3 (BYUVP 6233), right dentary with P/4, M/1 (BYUVP 6257), 2 right dentaries with M/1 (BYUVP 5974, 6304), 2 left dentaries with M/1 (BYUVP 6129, 6134). Three partial right maxillae with M1/ (BYUVP 6064, 6288, 6295) and a partial left maxilla with M1/ (BYUVP 6000) also compare favorably with this species.

Discussion--E. dorsalis is distinctly larger than E. minimus and slightly larger than E. umbrinus (Mead et al. 1982). It has a distinct isolated mesoconid on M/1 that is lacking in E. umbrinus and is part of an ectolophid in E. minimus (Miller 1976). The M/1's of the six dentaries listed above match E. dorsalis in this character, and the four maxillae listed above match best in size with E. dorsalis but cannot be positively distinguished from E. umbrinus. Of the larger chipmunks, only E. cf. umbrinus was reported from Smith Creek Cave (Mead et al. 1982), and I have found only E. dorsalis in Crystal Ball Cave. Their present ranges may account for this difference since E. umbrinus only inhabits the Snake Range west of Crystal Ball Cave while E. dorsalis inhabits the entire range (Hall 1981). Their ranges show that E. umbrinus is more isolated in areas of high elevation and more commonly absent from the areas once covered by Lake Bonneville.

Family Geomyidae
Thomomys umbrinus

Material--Anterior portion of skull with both I/'s (BYUVP 6656), anterior portion of skull with left I/ (LACM 123672), right dentary with /I, P/4, M/1 (BYUVP 6657), left dentary with P/4 (BYUVP 8283). Four palates without teeth (BYUVP 6653-6654, 6664-6665), 4 right dentaries without cheek teeth (BYUVP 6660, 6663, 6666, 8281), and 8 left dentaries without cheek teeth (BYUVP 6655, 6658-6659, 6662, 6681, 7009-7010, 8282) also compare favorably with this species.

Discussion--Thomomys is distinguished from other North American geomyids by the absence of a superficial groove on the anterior face of the upper incisors (illustrations in Hall 1981), and none of the I/'s listed above have this groove. T. umbrinus differs from T. talpoides and T. monticola, the only other species of Thomomys living in Nevada, Utah, or surrounding areas, by having a sphenoidal fissure, by not having the palatine foramina fully anterior to the anterior openings of the infraorbital canals (Durrant 1952), and by the absence of a lingual indentation in the anterior lobe of P/4 (Hall 1946). The two Thomomys skulls from Crystal Ball Cave have the sphenoidal fissure, and their palatine foramina are fully anterior to the infraorbital canals. The two P/4's also lack the lingual indentation as in T. umbrinus. My observations and also figures 308-321 in Hall (1946) indicate that T. umbrinus has a larger mean size than the other two species mentioned (contrary to Bergman's rule), and all the Crystal Ball Cave specimens compare best in size with the larger T. umbrinus.

T. umbrinus is the only geomyid currently inhabiting the Snake Range, and it is a southern species extending from Nevada and Utah southward into Mexico (Hall 1981). T. bottae and T. townsendii are now considered as subspecies of T. umbrinus (Hall 1981). T. talpoides, which inhabits mountain ranges to the east and west of the Snake Range, has Nevada and Utah as almost its southern boundary and extends northward into Canada. T. talpoides tends to inhabit higher elevations than T. umbrinus as well as higher latitudes. T. cf. talpoides is the only geomyid reported from Smith Creek Cave (Goodrich 1965).

Hall (1946) pointed out that although T. umbrinus is usually a lower elevation species than T. talpoides, T. umbrinus is the only geomyid in the Snake Range and occurs at all elevations (but is less abundant at higher elevations than T. talpoides is at similar elevations in other ranges). Hall (1946) attributed this to antiquity of occupancy and proposed that T. umbrinus, having no competitors in the Snake Range, developed populations adapted to higher elevations. Since T. umbrinus was the species best adapted to the valleys surrounding the Snake Range, no species which were better adapted to higher elevations could pass through to their favorable habitat. This could explain why the Crystal Ball Cave assemblage suggests no northward range shift for species of Thomomys as it does for other groups such as lagomorphs. If Hall (1946) is right, the tentative assignment of the Smith Creek Cave specimen to T. talpoides (Goodrich 1965) must be in error. Another possibility is that predatory birds transported the specimen to the cave, but this seems unlikely since T. talpoides occurs only as close as 45 miles (75 km) to the northwest and 108 miles (180 km) to the east of Smith Creek Cave. Hall (1946) also pointed out that geomyids, as individuals, are extremely sedentary, and this could be the cause of their slow invasion and northward retreat compared to other mammals.

Family Heteromyidae

Perognathus cf. formosus

Material--Partial right maxilla with P4/ (BYUVP 6682), 2 right dentaries with P/4 (BYUVP 6859, 6879), 2 right dentaries with M/2 (BYUVP 6711, 6856), left dentary with all teeth (BYUVP 6697), left dentary with P/4, M/1 (BYUVP 6786), left dentary with P/4, M/2 (BYUVP 6115).

Discussion--P. longimembris, P. parvus, and P. formosus now inhabit the Crystal Ball Cave area, and the closest other species range more than 150 miles (250 km) to the east and south (Hall 1981). Of the three local species, P. longimembris can be ruled out because its M/3 is distinctly smaller than its P/4 (Hall 1981), and BYUVP 6697 has the opposite condition. P. parvus and P. formosus are very similar dentally, and the Crystal Ball Cave specimens match well with both of them. P. formosus has a larger mean size than P. parvus, and the Crystal Ball Cave specimens compare best in size with P. formosus although P. parvus and several other western species cannot be ruled out. Miller (1979) referred all the Perognathus specimens found at Smith Creek Cave to P. cf. parvus, but since the identification was tentative at both caves, it does not seem wise to speculate about a possible difference between the two assemblages.

Microdipodops megacephalus

Material--Right maxilla with P4/, M1/,2/ (BYUVP 6695), right maxilla with P4/, M2/ (BYUVP 6781), right maxilla with M1/ (BYUVP 6709). Three partial right maxillae with P4/ (BYUVP 6669, 6674, 6797), a partial right maxilla with a partial M1/ (BYUVP 6759), a right dentary with /I, P/4, M/1 (BYUVP 6693), 2 right dentaries with P/4 (BYUVP 6795, 6860), and a left dentary with P/4 (BYUVP 6708) are of Microdipodops and compare favorably with M. megacephalus.

Discussion--Microdipodops is most similar to Perognathus but can be distinguished dentally by the molars having a single enamel loop as opposed to the biloph nature of Perognathus molars. The P/4's are also distinct in being more hypsodont and having a straight posterolabial border as opposed to the round and symmetrical nature of the Perognathus P/4's. M. megacephalus ranges throughout most of Nevada and into neighboring states including Utah, and it is currently found around Crystal Ball Cave (Hall 1981). M. pallidus, the only other species, occurs along the southern Nevada-California border more than 200 miles (320 km) southwest of Crystal Ball Cave (Hall 1981). M. megacephalus can be distinguished from M. pallidus by the latter possessing a small notch in the labial side of M1/, and all the Crystal Ball Cave specimens possessing the M1/ are clearly M. megacephalus. M. cf. megacephalus was reported at Smith Creek Cave (Miller 1979), and all heteromyid taxa recovered were low in abundance as at Crystal Ball Cave. This low abundance is probably due to a low density in life since even now they are rarely seen in the area.

Dipodomys microps

Material--Two right dentaries with /I (BYUVP 6672 and 8284), left dentary fragment with P/4 (BYUVP 6676). Nine maxillae without teeth (BYUVP 5593, 6667-6668, 6670, 6675, 6677-6680) and 2 right dentaries without teeth (BYUVP 6673, 6683) also compare favorably with this taxon.