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

In addition to Lake Bonneville, many pluvial lakes filled the valleys of Nevada including one just west of the Snake Range, 18 miles (30 km) west of Crystal Ball Cave (Mifflin and Wheat 1979). Based on studies of temperature and precipitation correlation, Mifflin and Wheat (1979) estimated that development of pluvial lakes in the area involved a temperature decrease of 5 F (3 C). Lower temperatures and higher annual precipitation caused floral boundaries to move lower in elevation and latitude during the Wisconsinan glacial (Thompson and Mead 1982, Wells 1983). This shift had a dramatic effect on small boreal mammals in the Great Basin because it allowed them to disperse between ranges, whereas now the intermontane basins act as absolute barriers (Brown 1971, 1978, Harper et al. 1978). Brown (1971, 1978) demonstrated that distribution of small boreal mammals is relectual from the Wisconsinan glacial and not a case of colonization-extinction equilibrium. The Crystal Ball Cave fauna shows what taxa have been extirpated from the Snake Range since the Wisconsinan glacial and documents northward shifts in the ranges of several species at the close of the Pleistocene.

Another striking feature of the late Pleistocene is the well-documented megafaunal extinction. At the end of the Wisconsinan glacial 41 species of large mammals went extinct--3 times more than at the end of any of the other Pleistocene glacials (Kurten and Anderson 1980). Different workers have attributed this to the rapid post-glacial climatic shift (Martin and Neuner 1978, Webb 1969) and to overkill by Early Man (Martin 1967, Mosimann and Martin 1975). The Crystal Ball Cave assemblage contains several of these extinct taxa, but the fact that it lacks human association and stratigraphic control makes it unable to provide any substantial data to resolve this controversy.

Consideration needs to be given to the role Crystal Ball Cave played as a shelter and the way fossils got into the cave. When the cave was discovered in 1956, the east entrance was a 3-foot (1-meter) diameter opening in solid rock, half filled with soft soil, which sloped downward into the large entrance chamber (see figure 3). Several 1-foot (0.3-meter) diameter entrances (which are often filled with woodrat nesting material) also exist just north of the east entrance. The north entrance was completely filled with debris, which if removed could make it 8 feet (2.5 meters) high and 20 feet (6 meters) wide. It could have been a large important entrance when the earlier bones were being deposited, but several factors preclude this. First, there are very few fossils in the deep dry sediments of the north half of the cave; the rich bone deposits are in the south half. Second, the fossil assemblage provides no evidence that there ever was a large entrance since large mammals are represented only by their smallest elements. If the north entrance ever was large it was probably prior to deposition of the fossils under study.

Neotoma lepida, Peromyscus maniculatus, and Plecotus townsendii were captured live inside the cave, so their presence in the assemblage is easy to explain. Other small mammals could also have lived in the cave or used it as a shelter. Small carnivores and scavengers could have brought their prey into the cave to eat. The presence of only the smallest isolated elements of large mammals suggests that these bones were brought into the cave individually after the carcasses deteriorated. Small carnivores could have contributed to this, but it is my opinion that these bones were taken into the cave primarily by wood rats, since they are known to take materials into the cave now and since all the bones in the assemblage are small enough for a wood rat to transport. Because the cave has small entrances and because the bones are found far within the cave, it is very unlikely that birds transported prey inside. There is also no evidence that prehistoric humans brought material into Crystal Ball Cave. This suggests that the species found in the assemblage lived and died in or near the cave and were not transported long distances, as could have occurred at Smith Creek Cave (see Bryan 1979, Harrington 1934).

It is unusual for caves to have their richest bone deposits far inside the cave rather than near an entrance. The east entrance takes in water during storms, and other areas are damp from seepage. Sites 1 and 2, which contain the richest bone deposits, are in one of the driest areas of the cave and are just outside the zone of total darkness when the sun shines through the east entrance. North of Sites 1 and 2 the passage constricts and enters total darkness but remains dry. Wood rat nests are particularly common at Sites 1 and 2, which helps explain why rich bone deposits are present if wood rats play an important role in getting them there. The extremely dry conditions at Sites 1 and 2 and their proximity to the east entrance, which I consider the primary entrance, are probably the reason why these sites have been so productive. Rarity of fossils nearer the east entrance is probably due to poorer preservational conditions and poorer sites for wood rat dwellings. Lack of rich bone deposits in the northern half of the cave is probably due to constricted passages and greater distance from a late Pleistocene entrance.

SYSTEMATIC PALEONTOLOGY

Kingdom Plantae
Division Tracheophyta
Class Gymnospermae
Family Ephedraceae
Ephedra cf. viridis

Material--Two stem fragments.

Class Angiospermae
Family Asteraceae
Chrysothamnus sp.

Material--One branching stem fragment.

Haplopappus nanus

Material--One group of involucres, 4 single involucres.

Perityle stansburii

Material--Four involucres on stem fragments.

Family Brassicaceae

Material--Two stem fragments, 2 stem fragments with empty seed capsules, 4 empty seed capsules.

Family Cactaceae
Opuntia sp.

Material--Twelve spines.

Family Caprifoliaceae
Symphoricarpos cf. longiflorus

Material--One branching stem fragment, 4 straight stem fragments, 56 leaves and partial leaves.

Family Poaceae
cf. Elymus

Material--Two fruits.

cf. Panicum

Material--Three connected fruits, 3 rachis fragments.

Discussion--About 250 small plant fragments were recovered from the Crystal Ball Cave sediments by the same process that small bones and teeth were recovered. From among them Howard C. Stutz (1984 personal communication), a botanist at Brigham Young University, identified the above taxa. All of the taxa identified still live in the immediate area of Crystal Ball Cave (partly because a sample of plants from immediately around the cave comprised most of the comparative material), so they do not document any floral changes since the Pleistocene. Further research could turn up additional taxa since not all the plant fragments were identified.

The great abundance of Symphoricarpos compared to the other plant taxa recovered is noteworthy. H. C. Stutz (1984 personal communication) found a thicket of Symphoricarpos at the bottom of a cliff in the nearby House Range which was full of rodent nests and burrows. This suggests that this plant is a favorite nest building material for rodents, and wood rats may have brought a lot of it into Crystal Ball Cave for that purpose.

No pollen analysis has been done at Crystal Ball Cave, and no pollen was noticed in the cave sediments studied. A more extensive search could turn up pollen, however, and since plant fragments are rare in the sediments, it could help identify what plants inhabited the area during the Pleistocene.

Kingdom Animalia

Phylum Mollusca
Class Gastropoda
Order Pulmonata
Family Helicidae
Oreohelix strigosa

Material--Nine complete shells ranging from 3 to 10 mm in diameter.

Discussion--These land snails, which still inhabit the Snake Range, live in moister conditions than those at Crystal Ball Cave today (Chamberland and Jones 1929), so they are probably late Pleistocene or early Recent in age. Since there are only nine specimens, they were probably never abundant near the cave and may have even been transported some distance before being deposited.

Phylum Arthropoda

Class Crustacea
Order Isopoda
Family ? Armadillidae

Material--Partial dried shell.

Discussion--Pill bugs are native to North America (S. L. Wood 1984 personal communication), and little work has been done on them. Representatives of several families including family Armadillidae presently live in Utah, but the partial specimen did not allow further identification. These terrestrial crustaceans inhabit moist recesses throughout Utah and Nevada today, so the presence of this specimen is not surprising although little can be said about its age.

Class Insecta

Order Coleoptera
Family Scarabaeidae
Aphodius distinctus

Material--Complete dried specimen.

Discussion--This small beetle lives in cattle dung and was introduced from Europe in Recent times (S. L. Wood 1984 personal communication). It is therefore Recent in age and has little significance to the assemblage.

Phylum Chordata

Class Osteichthyes
Infraclass Teleosti

Material--Thirty-seven amphicoelous vertebrae ranging from 1 to 5 mm in diameter and length (BYUVP 7939-7973).

Discussion--Presently the closest water body to Crystal Ball Cave is Gandy Spring on the south side of Gandy Mountain. This spring emits voluminous warm (81 F, 27 C) water which is high in calcium (J. C. Bates 1983 personal communication). Small minnows were the only native fish found living in the stream that exits Gandy Spring, but bass and blue gill were introduced in the 1960's and still survive; carp are also found in reservoirs in the area (J. C. Bates 1984 personal communication). Mead et al. (1982) reported Salmo and Gila from nearby Smith Creek Cave which is higher in elevation and farther from a perennial water source than Crystal Ball Cave, and Smith (1978) and Smith et al. (1968) reported Pleistocene fish from Lake Bonneville deposits.

A dichotomy in the size of the fish vertebrae from Crystal Ball Cave suggests that at least two species are represented, but no attempt at generic identification has been made. The possibility that these vertebrae are Recent cannot be eliminated, but they probably represent fish that lived in Lake Bonneville when it was at or near the Bonneville level, or in perennial Pleistocene streams in the area. In any case they had to be transported up Gandy Mountain to the cave site. Carnivores or scavengers could have done this, and wood rats could have taken them inside the cave.

Class Reptilia
Order Squamata

Material--Two hundred and sixty-five lizard and snake jaws (BYUVP 8004-8217). Postcranial material is also represented but has not been separated from that of mammals.

Discussion--The reptile specimens have not yet been studied but will be reported in a future paper by Jim I. Mead and Timothy H. Heaton. The reptiles recovered from the deeper levels of Smith Creek Cave demonstrate that their present distribution in the Great Basin is more ancient than previously believed (Brattstrom 1976, Mead et al. 1982). The large number of reptile jaws from Crystal Ball Cave will help establish what species have been extirpated from the area, but unless dated individually, they will not help establish the antiquity of their ranges.

Class Aves

Material--Six hundred and eleven specimens representing all skeletal elements of small passerines and skull and vertebrae fragments of larger forms (BYUVP 6606, 8301-8888, 8911-8933, LACM 123655).

Discussion--The bird specimens have not yet been studied but will be reported in a future paper by Steven D. Emslie and Timothy H. Heaton. Miller (1982) reported ? Aquila from Crystal Ball Cave from among this same material. Based on their large size, three bird vertebrae fragments (BYUVP 8326-8328) can possibly be assigned to the extinct Teratornis incredibilis, originally described from nearby Smith Creek Cave (Howard 1952).

Class Mammalia
Order Insectivora
Family Soricidae
Sorex sp.

Material--One maxilla pair with all teeth (BYUVP 5321). Another 5 partial maxillae and 27 partial dentaries (some with teeth, BYUVP 5300-5320, 5322-5332) were recovered that cannot be generically identified but compare favorably with Sorex.

Discussion--Identification was based on the presence of 5 unicusp teeth behind the upper incisor, the first 4 of which taper slightly in size posteriorly and are visible laterally, and the last of which is tiny, peglike, unpigmented, and not visible labially. Microsorex and Blarina also have 5 unicusp teeth in each maxilla, but Microsorex has only the first 3 visible laterally and Blarina has the third and fourth of subequal and smaller size than in Sorex. Notiosorex and Criptotis, the other two North American genera, have only 3 and 4 unicusp teeth in each maxilla respectively (Hall 1981). All the other soricid specimens are either lower jaws and teeth, which I was unable to distinguish at the generic level, or are maxillae without the diagnostic unicusp teeth. All these soricid specimens compare well with S. vagrans and S. palustris, which presently live in the region of the cave (Hall 1981), but no dental character could be found to distinguish them.

Order Chiroptera

Family Vespertilionidae
Myotis sp.

Material--Two palates without teeth (BYUVP 5340, 5357), anterior portion of right maxilla with P4/, M1/ (BYUVP 5338). Twelve right dentaries (BYUVP 5336, 5341-5346, 5352, 5353, 5358-5360) and 12 left dentaries (BYUVP 5339, 5347-5349, 5354-5356, 5361-5364, 5366) were recovered which are Myotis or Plecotus.

Discussion--Myotis maxillae have the diagnostic presence of two
small unicusp premolars following the incisor, as opposed to one or none in all other vespertilionids. Dentaries of Myotis and Plecotus are virtually identical, both having the dental formula of I/3, C/1, P/3, P/3 and similar size and proportions, and no character could be found to separate them. Dentaries of Lasionycteris and Pizonyx also share this tooth formula but are considerably larger. Myotis has not been reported living in Crystal Ball Cave, but M. lucifugus, M. evotis, M. thysanodes, M. volans, and M. subulatus are all found in the region (Hall 1981). Little work has been done to separate species of Myotis dentally, and I was unable to find any species variation that was greater than individual variation.

? Plecotus townsendii

Material--Twenty-four dentaries were recovered of Myotis and/or Plecotus (as listed and discussed above).

Discussion--Plecotus townsendii is the only bat reported living in the cave. Specimens were captured by Halliday (1957) and by myself in 1982 and 1983. Halliday (1957) and other workers have referred this bat to Corynorhinus rafinesquii, but Handley (1959), in his synthesis of the big-eared bats, considers both Corynorhinus and Idionycteris as only subgenera of the European genus Plecotus. He also regards P. rafinesquii (presently in southeastern U.S.) and P. townsendii (presently in western U.S.) as two distinct species. P. mexicanus, the third living species of the subgenus (Corynorhinus), and P. hyllotis, the only member of the subgenus (Idionycteris), both inhabit Mexico and north into the southern tip of Arizona. Two extinct Pleistocene species of the subgenus (Corynorhinus) are also recognized: P. alleganiensis from Cumberland cave in Maryland and P. tetralophodon from San Josecito Cave in Mexico (Handley 1959). Handley (1959) lists no characters to distinguish the dentaries of different species of Plecotus, but the bats living in the cave are clearly P. townsendii.

Lack of positive evidence for this species in the Crystal Ball Cave assemblage could represent lack of chance preservation or a recent change in the species that inhabit the cave. Since the assemblage contains indistinguishable Pleistocene and Recent specimens, even if the lower jaws could be identified as Plecotus they would not reveal how long this species has inhabited the cave. Humphrey and Kunz (1976) postulated that mild winters during the late Pleistocene allowed P. townsendii to roost in trees rather than caves and to avoid the present habit of long winter hibernation, whereas this bat now use caves as refugia to survive the intolerably cold post-Pleistocene winters. Humphrey and Kunz (1976) cited evidence that this bat is very sedentary and now survives only in isolated areas where suitable winter hibernacles are available. Handley (1959) stated that very few specimens of Plecotus townsendii have been reported considering its large geographic range. Durrant et al. (1955) said this species was thought to only inhabit the southern half of Utah until a few isolated citings were made in northern Utah caves, one of which (in Logan Canyon) contained the bat in large numbers. It is, therefore, very possible that P. townsendii has not inhabited Crystal Ball Cave, at least to the large degree that it does now, until Recent times.

Antrozous pallidus

Material--Anterior portion of left maxilla with C1/, P4/ (BYUVP 5365), anterior portion of fused dentary pair with left P/4, M/1 (BYUVP 5351), posterior portion of right dentary with M/2 (BYUVP 5333), posterior portion of left dentary with M/1 (BYUVP 5334). A posterior fragment of a left dentary (BYUVP 5350) and a right M/2 (BYUVP 5335) probably also belong to this taxon based on their large size and chiropteran affinities.

Discussion--This is the largest species of bat found in the assemblage and is easily distinguishable from other vespertilionids by its unique tooth formula of I1/2, C1/1, P1/2, M3/3, the configuration of the incisors and fenestra in the anterior palate, and the high coronoid process on the dentary. A. pallidus has not been reported living in the cave, but it presently occurs from the region of the cave southward into Mexico and along the west coast of the United States and southern British Columbia. A. bunkeri is now considered a subspecies of A. pallidus (Hall 1981). A. dubiaquercus occurs in Mexico and Central America and is distinguished from A. pallidus by normally having 3 lower incisors instead of 2. A. koopmani occurs only in Cuba. All the material listed above matches perfectly with modern A. pallidus which lives in the region of Crystal Ball Cave.

Order Lagomorpha
Family Ochotonidae
Ochotona princeps

Material--Anterior portion of skull with all teeth (BYUVP 5387), right maxilla with M/1,/2 (BYUVP 5407), right maxilla with M/2 (BYUVP 5406), right maxilla without teeth (BYUVP 5385), anterior portion of right maxilla with M/1 (BYUVP 5404), 2 anterior portions of right maxillae without teeth (BYUVP 5386, 5405), 4 partial right maxillae without teeth (BYUVP 5368, 5409, 5410, 5412), 6 left maxillae without teeth (BYUVP 5381, 5383, 5384, 5396, 5397, 5417), 3 anterior portions of left maxillae without teeth (BYUVP 5374-5376), 5 partial left maxillae without teeth (BYUVP 5369, 5382, 5408, 5415, 5416), right dentary with P/4, M/2,/3 (BYUVP 5399), right dentary with M/2,/3 (BYUVP 5393), right dentary with M/2 (BYUVP 5395), 5 right dentaries without teeth (BYUVP 5390-5392, 5401, 5419), partial right dentary with P/4 (BYUVP 5370), 4 partial right dentaries without teeth (BYUVP 5367, 5411, 5413, 5414), 2 anterior portions of right dentaries without teeth (BYUVP 5371, 5372), left dentary with P/4, M/1,/2 (BYUVP 5402), left dentary with M/1,/2 (BYUVP 5398), 3 left dentaries without teeth (BYUVP 5394, 5403, 5418), anterior portion of left dentary with P/4, M/1,/2,/3 (BYUVP 5388), posterior portion of left dentary with M/1,/2,/3 (BYUVP 5389), 2 posterior portions of left dentaries without teeth (BYUVP 5377, 5400), partial left dentary with M/1,/2 (BYUVP 5378), 3 partial left dentaries without teeth (BYUVP 5373, 5379, 5380).

Discussion--Ochotonids are easily distinguished from leporids by the lingual curve in the maxilla behind the cheek teeth, the presence of 5 upper cheek teeth rather than 6, and M/3 and its socket being anteroposteriorly short instead of triangular. O. princeps presently inhabits high elevations within 120 miles (190 km) of Crystal Ball Cave, both to the east and west (Hall 1981). The only other extant species, O. collaris, occurs only in northwestern Canada and Alaska (Hall 1981) and has been found in fossil deposits only in that region (Kurten and Anderson 1980). The only known extinct North American species of Ochotona is O. whartoni, which is known only from the early Pleistocene and is distinctly larger than the extant species (Kurten and Anderson 1980). All the specimens listed above are indistinguishable from Recent O. princeps.

Why O. princeps has been extirpated from the Snake Range is uncertain, but fossils have been recovered from Smith Creek Cave (Miller 1979) and many other Great Basin localities where this species does not live today. For example, Grayson (1977) recovered O. princeps dated at 7,000 to 12,000 Y.B.P. from the Fort Rock Basin of south-central Oregon. The area is now dominated by sagebrush, grasses, and sparse junipers, but modern pikas in the region only live where there is more succulant vegetation. Grayson (1977) attributed the disappearance of Ochotona to either a shift to more xeric habitat or to an eruption of Mt. Mazama 7,000 years ago. A similar extirpation in the Snake Range 315 miles (500 km) to the southeast supports the former of Grayson's hypotheses.

Family Leporidae
Sylvilagus idahoensis

Material--Right dentary with P/4, M/1,/2 (BYUVP 5534), right dentary without teeth (BYUVP 5444), right dentary fragment with P/3 (BYUVP 5584), left dentary with P/3,/4, M/1 (BYUVP 5536), left dentary fragment without teeth (BYUVP 5434).

Discussion--S. idahoensis is distinguished from all other leporids by its small size (see figure 4) and from Ochotona by the characters listed above. The P3/ of S. idahoensis does not widen posteriorly, as in other species of Sylvilagus, and the second reentrant angle is not crenulated as it is in many leporids. BYUVP 5536 is larger than any of the Recent S. idahoensis specimens to which it was compared (but smaller and distinct from other species of leporids), and the other specimens are also comparatively large, suggesting that this species may have decreased in size at the end of the Pleistocene. This species presently occurs in the region of the cave and to the north and west (Hall 1951, 1981).

Sylvilagus nuttallii

Material--Anterior portion of right dentary without teeth (BYUVP 5493), left dentary with M/1 (LACM 123658), anterior portion of left dentary with I/1, P/3,/4, M/1 (BYUVP 5578), four right P/3's (BYUVP 5717, 5731, 5769, and 5794), four left P/3's (BYUVP 5773, 5782, 5795, 5810).

Discussion--Sylvilagus is commonly distinguished from Lepus by its smaller size, although there is some overlap (namely, S. aquaticus and S. cunicularius are larger than L. americanus; J. A. White 1984 personal communication). The species of these genera presently living in the region are usually discernible by size, but the species within each genus are usually not (see figure 4).

Of the two species of Sylvilagus presently living in the Snake Range, S. audubonii has a larger mean size and tends to have much more crenulation in the second reentrant angle of P/3 than S. nuttallii (although there is overlap in both characters). S. floridanus, which occurs just south of Utah and Nevada, has an even larger mean size than S. audubonii but has little crenulation in the P/3 like S. nuttallii. BYUVP 5493 and LACM 123658 compare well in size with S. nuttallii and S. audubonii (see figure 4), but none of the nine P/3's of Sylvilagus size have much crenulation in the second reentrant angle of P/3, suggesting that they belong to S. nuttallii rather than S. audubonii. Although other species could be represented, the evidence suggests that at least the majority of the specimens listed above are of S. nuttallii.