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

Discussion--Dipodomys is distinctly larger than other heteromyid genera. D. microps is distinguished from other species of Dipodomys by having chisel-shaped lower incisors (anterior face flat) rather than awl-shaped lower incisors (anterior surface round), and the incisors of BYUVP 6672 and 8284 are chisel-shaped. P/4 is also distinct in having a larger and more isolated anterior loph than D. ordii or D. merriami but not a complete separation of lophs as in D. deserti, and the P/4 of BYUVP 6676 clearly matches D. microps. The referred specimens also match perfectly with Recent D. microps, but lack the diagnostic teeth. Of the four species of Dipodomys presently living in Utah and Nevada, D. microps and D. ordii are found in the Snake Range while D. merriami and D. deserti occur more than 125 miles (200 km) to the south and west (Hall 1981). D. microps has a much smaller range than D. ordii, occurring only in Nevada and parts of surrounding states (Hall 1981). The Dipodomys specimens recovered from Smith Creek Cave (Miller 1979) were referred to D. ordii because they had awl-shaped lower incisors. This difference between the two assemblages is difficult to explain because the range differences between these species do not suggest distinct differences in habitat preference.

Family Cricetidae

Peromyscus maniculatus

Material--Right maxilla fragment with M1/,2/ (BYUVP 6703), left maxilla with M1/,2/,3/ (BYUVP 6782), left maxilla fragment with M1/,2/ (BYUVP 6771). Thirty nine Peromyscus dentaries containing one or more molars compare favorably with P. maniculatus and P. crinitus.

Discussion--Of the six species of Peromyscus that inhabit Utah and Nevada, only P. maniculatus, P. truei, and P. crinitus currently live around Crystal Ball Cave (Hall 1981). P. maniculatus was captured live inside the cave by the author in 1982 and 1983. Peromyscus fossils from Smith Creek Cave were not identified to the species level (Goodrich 1965, Mead et al. 1982, Miller 1979). Dental characters which distinguish species of Peromyscus are few and not always reliable. P. maniculatus and P. truei belong to the subgenus Peromyscus, which has accessory tubercles or enamel loops on the labial side of M1/ and M2/; P. crinitus belongs to the subgenus Haplomyomys which lacks these features (Hall 1981). I found this character to be quite reliable, and the specimens listed above all have prominent cusps on M1/ and M2/. In further refinement of this character, Miller (1971, 1976) was able to separate P. maniculatus from all other western species of Peromyscus by the presence of an anteroconule on M1/ with direct attachment to the anterocone rather than being joined to it by a distinct loph as in P. truei. Specimens listed above fit P. maniculatus in this respect. Species of the subgenus Haplomyomys usually lack the anteroconule entirely (Hall 1981, Miller 1971, 1976). Unfortunately, excessive wear on the teeth erases this character.

Of the 40 Peromyscus dentaries containing one or more molars, 39 compare best in size with the smaller P. maniculatus and P. crinitus, but no character could be found to separate these species based on dentaries. Miller (1976) found the P/3's of P. maniculatus, P. crinitus, and P. eremicus to be relatively more reduced than P. boylii and P. truei. The 8 Crystal Ball Cave Peromyscus dentaries containing M/3 tend to have M/3 relatively reduced as in P. maniculatus, P. crinitus, and P. eremicus, and in size all the 39 dentaries listed above compare best in size with the smaller P. maniculatus and P. crinitus.

Peromyscus cf. crinitus

Material--Right maxilla with M1/,2/ (BYUVP 6780), left maxilla with M1/,2/ (BYUVP 6769), left maxilla with M1/ (BYUVP 6715). Thirty nine Peromyscus dentaries containing one or more molars compare favorably with P. maniculatus and P. crinitus.

Discussion--These specimens lack accessory tubercles and enamel loops on the 2 principle outer angles of M1/ and M2/, so they probably belong to the subgenus Haplomyomys (Hall 1981). Of the two species of Haplomyomys found in Utah, P. crinitus and P. eremicus, the Crystal Ball Cave specimens compare better in size with the smaller P. crinitus (although there is considerable overlap). Some of the 39 dentaries discussed under P. maniculatus (above) could also belong to this species since no character was found to distinguish them based on dentaries. P. crinitus is presently found around the cave while P. eremicus only ranges as close as 135 miles (225 km) to the south (Hall 1981), and this further suggests that these specimens are P. crinitus.

Peromyscus cf. truei

Material--Left dentary with M/1 (BYUVP 6718).

Discussion--P. truei is the largest species of Peromyscus living in Utah and Nevada (Durrant 1952, Hall 1981), and the M/1 listed above compares well in size with this species and is larger than the mean size of P. eremicus and P. boylii and distinctly larger than any P. maniculatus or P. crinitus M/1's examined. Identification is based only on size since no other character could be found to distinguish M/1's of Peromyscus. This species is found throughout the Great Basin, so its presence in the assemblage is not surprising.

Neotoma lepida

Material--Partial skull without teeth (LACM 123671), 2 partial right maxillae with M1/ (BYUVP 7045, 7065), 2 left maxillae with M1/ (BYUVP 7154), partial left maxilla with M1/ (BYUVP 7246).

Discussion--N. lepida and N. cinerea are the only species of Neotoma that presently inhabit the Snake Range (Hall 1946, 1981). Of three wood rats that I trapped in Crystal Ball Cave and two elsewhere on Gandy Mountain in 1982 and 1983, all were N. lepida. I did trap a N. cinerea in another cave in the Snake Range 22 miles (35 km) south of Crystal Ball Cave, so they are known to inhabit caves in the area. Miller (1979) reported both N. lepida and N. cinerea from Smith Creek Cave but did not comment on their relative abundance. Of these two species, N. cinerea is much more boreal than N. lepida, having a more northern range and being found at higher elevations (Finley 1958, Hall 1946, 1981). Durrant (1952) and Hall (1981) also reported N. albigula, N. mexicana, and N. stephensi living in Utah but far south and east of Crystal Ball Cave.

Neotoma cinerea is usually distinguishable from N. lepida by its larger size and deeper anterolabial reentrant angle on M1/ (Finley 1958). According to Hall (1946), the maxillary alveolar length is always 8.8 mm or less in N. lepida and 9.1 mm or more in N. cinerea for the Nevada subspecies, and Finley (1958) reported only a slight overlap for the Colorado subspecies. The three other Utah species of Neotoma are intermediate in size between N. lepida and N. cinerea, and N. albigula has the M1/ pattern of N. lepida while N. mexicana and N. stephensi have the M1/ pattern of N. cinerea (Finley 1958). Because these are the most diagnostic characters, only maxillae with M1/ and/or a measurable alveolar length were considered.

The Crystal Ball Cave specimens listed above compare best in size with N. lepida, the only species of Neotoma known to presently inhabit the cave. Maxillary alveolar lengths of Neotoma specimens from the cave show a strongly bimodal distribution, suggesting that N. albigula, N. mexicana, and N. stephensi are not represented since they are intermediate in size between N. lepida and N. cinerea. The shallow anterolabial reentrant angle of the M1/'s also compares favorably with N. lepida. The scarcity of N. lepida specimens in the assemblage suggests that this species probably has not always inhabited the cave as it does now.

Neotoma cinerea

Material--Anterior portion of skull with both I/, M1/,2/ (BYUVP 7384), maxilla pair with all teeth except left I/ (BYUVP 7281), maxilla pair with right M1/,2/,3/, left M1/,2/ (BYUVP 7282), maxilla pair with both M1/,2/ (BYUVP 7067), maxilla pair with right M/1,/2 (BYUVP 7015), maxilla pair with left M/1 (BYUVP 7213), 9 right maxillae with M1/,2/,3/ (BYUVP 7136, 7149, 7158, 7167, 7214, 7248, 7254, 7314, 7320), 3 right maxillae with M1/ (BYUVP 7273, 7316, 7330), 25 partial right maxillae with M1/ (BYUVP 7014, 7018, 7024, 7038, 7046, 7104, 7114, 7125, 7134, 7138, 7147, 7170, 7177, 7180, 7182, 7197, 7204, 7216, 7242, 7247, 7249, 7276, 7344, 7348, 7349), 10 right maxillae without teeth (BYUVP 7255, 7343, 7353, 7367, 7377, 8286-8290), 7 left maxillae with M1/,2/,3/ (BYUVP 7095, 7212, 7250, 7257, 7274, 7376, 7379), 4 partial left maxillae with M1/,2/ (BYUVP 7101, 7174, 7179, 7324), partial left maxilla with M1/,2/ (BYUVP 7017), 34 partial left maxillae with M1/ (BYUVP 7021, 7061, 7062, 7072, 7073, 7087, 7099, 7106, 7133, 7140, 7142, 7144, 7145, 7151, 7162-7164, 7172, 7175, 7183, 7189, 7200, 7205, 7217, 7220, 7225, 7267, 7300, 7317, 7318, 7322, 7351, 7362, 7371), 6 left maxillae without teeth (BYUVP 7171, 7346, 8291-8294). Another approximately 200 maxillae, 200 dentaries, and 2,000 isolated molars compare best with this species.

Discussion--Neotoma cinerea is recognized by its large size and deep anterolabial reentrant angle on M1/ as discussed above. N. cinerea has the largest mean size of any species of Neotoma, and all the specimens listed above match Recent N. cinerea in size and have he deep anterolabial reentrant angle on M1/ when this tooth is present. This makes N. cinerea the second best represented species in the Crystal Ball Cave assemblage after Spermophilus townsendii. The fact that N. cinerea is abundant in the assemblage, but not found in the cave now, while N. lepida is rare in the assemblage, but now the only wood rat living in the cave, suggests that a replacement of N. cinerea by N. lepida has recently taken place in the area. The great abundance of N. cinerea remains at Sites 1 and 2 of Crystal Ball Cave also helps substantiate my hypothesis that wood rats were the primary means of transporting fossils, especially of large mammals, into the cave. The dominance of N. cinerea over N. lepida in the assemblage suggests that N. cinerea was the primary species involved in this transport.

The ecological differences between N. cinerea and N. lepida have significance both to the replacement of the former species by the latter and to the accumulation of fossils in the cave. Finley (1958), in his detailed study of Colorado wood rats, found den sites to be the most limited resource for all species. Since all wood rats prefer the same basic types of den sites, namely rocky crags and caves, multiple species are rarely found coexisting (Finley 1958). This suggests that when conditions at Crystal Ball Cave reached a threshold where they favored N. lepida over N. cinerea, the replacement took place quickly. N. cinerea prefers higher elevations and latitudes than N. lepida, and hot summers in arid regions seem to be a limiting factor for this species (Finley 1958, Hall 1981). The changing conditions that led to the replacement of N. cinerea by N. lepida may have been the increase in temperature and decrease in moisture at the close of the Pleistocene, the shift in vegetation caused by it, or both. Regarding food, Finley (1958) stated that N. cinerea prefers soft-leaved shrubs, forbs, and montane conifers, whereas N. lepida prefers xerophytic shrubs, forbs, cacti, and shrubby trees.

Species of Neotoma differ somewhat in den preferences and collecting habits. Finley (1958) stated: "Dens of N. cinerea are usually in high vertical crevices in cliffs or caves, whereas those of . . . N. lepida are usually in low horizontal crevices or under boulders or large fallen blocks. Dens of [N.] cinerea usually contain larger accumulations of sticks and bones." That N. cinerea collects more material, especially bone, is very significant since I consider wood rats as the primary mechanism of fossil deposition at Crystal Ball Cave. This suggests that the rate of bone deposition decreased when N. lepida replaced N. cinerea, and it helps explain why many elements of the present local fauna are so poorly represented and why all the dated fossils were late Pleistocene rather than Recent in age.

A replacement of N. cinerea by N. lepida parallels the replacement of Sylvilagus nuttallii by S. audubonii and Lepus townsendii by L. californicus (discussed above) and helps confirm that a warming trend took place in the recent past. Although N. cinerea still lives in the area, it seems to have been driven to higher elevations in the Snake Range.

Ondatra zibethicus

Material--Palate without teeth (BYUVP 7383), partial right dentary with anterior 2/3 of M/1 (BYUVP 7391).

Discussion--Ondatra is easily distinguished from other microtine rodents by its large size combined with rooted molars. O. zibethicus is now considered the only extant species of Ondatra (Hall 1981), and the Crystal Ball Cave specimens are indistinguishable from this species. A number of fossil species have been named, but there is considerable confusion about their status (Miller 1976). All the extinct species considered valid by Semken (1966) and Nelson and Semken (1970) are smaller than O. zibethicus. The Crystal Ball Cave dentary is almost as large as the largest O. zibethicus to which it was compared. The M/1 is 7.9 mm long and 2.5 mm wide which best matches measurements taken from Wisconsinan-age O. zibethicus specimens (Nelson and Semken 1970). The palate is slightly smaller than the mean of O. zibethicus but well within its range of variation.

O. zibethicus is not presently found around Gandy but occurs as close as 100 miles (170 km) to the north, east, and south (Hall 1981). Since Ondatra is a reliable indicator of permanent water (Nelson and Semken 1970), the retreat of Lake Bonneville and loss of perennial streams in the area probably lead to its extirpation from the Snake Range.

Microtus cf. longicaudus

Material--Two left M3/'s (BYUVP 6940 and 6981), 7 right M/3's (BYUVP 8220-8226), 15 left M/3's (BYUVP 7002, 8227-8241). Numerous other partial jaws and isolated molars cannot be distinguished from Lagurus but lack characters that would assign them to other species of Microtus, some of which are likely Microtus since over a third of the microtine M/3's belong to Microtus. Among these are a partial skull with both M1/,2/ and the posterior incisive foramina (BYUVP 8285) and a right maxilla with M1/,2/ (BYUVP 6943).

Discussion--Microtus differs from Lagurus, the only other microtine of its size with rootless molars, in having 3 transverse loops on M/3 rather than 4 prisms, some of which are closed triangles, and in having a large semicircular posterior loop on M3/ rather than a simple elongate loop (Hall 1981). The 2 M3/'s and 22 M/3's from Crystal Ball Cave listed above clearly match Microtus in this respect. There are many species of Microtus, some of which have distinct dental characteristics and some of which do not.

The only two species of Microtus now inhabiting the Snake Range are M. longicaudus and M. montanus, and no character could be found to distinguish them dentally. The incisive foramina of M. longicaudus are not constricted posteriorly as are those of M. montanus, but they differ from those of Lagurus only in having slightly curved rather than straight external margins. Since only the posterior end of the incisive foramina are found on skulls that could be Microtus from Crystal Ball Cave, skulls of M. longicaudus in the collection are indistinguishable from Lagurus. Of 13 skulls containing incisive foramina which may be Microtus, 2 have constricted incisive foramina as in M. montanus (listed below), and 11 compare well with M. longicaudus and Lagurus.

Three other species of Microtus presently occur in Utah but not in the Snake Range: M. pennsylvanicus and M. richardsonii in the central mountain ranges and M. mexicanus in the southwestern corner of the state. M. pennsylvanicus has a posterior loop on M2/ not found in other species, and this character was only found on one specimen (listed below). M. richardsonii is distinctly larger than the other species described here, and none of the microtine specimens from Crystal Ball Cave are large enough to compare with it. M. mexicanus is dentally indistinguishable from M. montanus and M. longicaudus, and its incisive foramina are identical to Lagurus and similar to M. longicaudus.

The specimens listed above are identical to Recent specimens of M. longicaudus, M. mexicanus, and more distant ranging species. But since M. longicaudus presently occurs at Crystal Ball Cave, while M. mexicanus occurs more than 250 miles (400 km) to the southeast (Hall 1981), and because the general trend in the region is for range boundaries to be migrating northward, the Crystal Ball Cave specimens (except the few discussed below) are referred to M. longicaudus.

Microtus cf. montanus

Material--Two partial palates without teeth which include the posterior end of the incisive foramina (BYUVP 8218, 8219).

Discussion--M. montanus is the only microtine of its size presently occurring in Utah or Nevada with incisive foramina that abruptly constrict posteriorly and are narrower posteriorly than anteriorly. The posterior ends of the incisive foramina in these two specimens are too narrow to be M. longicaudus, M. pennsylvanicus, M. mexicanus, or Lagurus curtatus. M. townsendii and M. oregoni also have incisive foramina like M. montanus, but they both occur only along the pacific coast from northern California to southern British Columbia. Since M. montanus presently occurs in the Snake Range (Hall 1981), the Crystal Ball Cave specimens are referred to it. M. montanus tends to occur at higher elevations than other species of Microtus in Utah (Durrant 1952), so its presence in the assemblage suggests that conditions at the cave during the Late Pleistocene may have been like those of higher elevations in the Snake Range now.

Microtus cf. pennsylvanicus

Material--Partial skull with right M1/,2/ (BYUVP 6973).

Discussion--M. pennsylvanicus is unique in having a rounded posterior loop behind the 4 closed angular sections of M2/. This single specimen from the assemblage has this posterior loop, but the loop is not completely closed off from the preceding triangle as in the Recent specimens to which it was compared. Since the distinguishing character is not fully developed, the specimen is only referred to M. pennsylvanicus. This species is not presently found in the Snake Range, but it occurs 114 miles (190 km) east of Crystal Ball Cave in the mountains of central Utah and is a northern species (Hall 1981). Considering the climatic shifts since the recession of Lake Bonneville, it is not unlikely that it could have inhabited the Snake Range during the Late Pleistocene.

Lagurus curtatus

Material--Skull with right I/, M2/,3/, left I/, M1/,2/ (BYUVP 6899), left dentary with M/1,/2,/3 (BYUVP 6977), left dentary with M/2,/3 (BYUVP 6986), 28 right M/3's (BYUVP 8242-8270), 9 left M/3's (BYUVP 8271-8280). Numerous partial jaws and isolated molars may be L. curtatus but cannot be distinguished from Microtus longicaudus (as discussed above).

Discussion--The differences between Lagurus and Microtus are discussed above. L. curtatus, the only North American species of Lagurus, is distinguished from Old World representatives by having 4 instead of 5 closed triangles on M/3 and cement present in the reentrant angles of the molars (Hall 1981). This species presently occurs in the Snake Range and northward into Canada (Hall 1981). Lagurus specimens are nearly twice as abundant as those of Microtus in the assemblage, but since no information on their Recent relative abundance or habitat differences could be found, it is difficult to know the reason for this.

Order Carnivora
Family Canidae
Canis cf. latrans

Material--Lower incisor (BYUVP 7459), right C/1 (LACM 123675), partial left M/1 (BYUVP 7460). The frontal region of a skull (LACM 123676) and an anterior fragment of a left dentary without teeth (BYUVP 7458) also compare favorably with this species.

Discussion--These specimens are indistinguishable from specimens of Recent C. latrans, generally recognized as the only species of coyote in the Pleistocene or Recent (Giles 1960). Dentally, C. latrans falls within the wide range of variation of the domestic dog, C. familiaris (Anderson 1968), so the possibility that the Crystal Ball Cave specimens are C. familiaris cannot be totally eliminated. But C. latrans is presently very abundant around the cave (J. C. Bates 1983 personal communication, Hall 1981) and has been recognized from nearby Pleistocene assemblages that have better stratigraphic control (Kurten and Anderson 1972, Miller 1979), so there is no reason to believe it would not be found in the assemblage. Also, domestic dogs tend to have many more tooth malformations than coyotes (Anderson 1968) and none are seen in the Crystal Ball Cave specimens. Lack of human fossils and artifacts at Crystal Ball cave makes domestic dogs less likely to be present than at sites that contain such remnants of human occupation. Although residents of Gandy have domestic dogs that sometimes roam on Gandy Mountain, the lack of any canid specimens in the assemblage that cannot be referred to native species also supports the conclusion that the Crystal Ball Cave specimens are C. latrans.

Canis cf. lupus

Material--Partial right M1/ (BYUVP 7455), left P/1 (BYUVP 7457),

posterior end of right M/1 (BYUVP 7456), left M/1 (LACM 123674), axis (LACM 123710).

Discussion--Identification of these canid fossils is based on their size, being substantially larger than C. latrans but considerably less robust than C. dirus. They do, however, fit within the large size range of C. familiaris, so the identification must be tentative. Goodrich (1965) reported C. lupus from Smith Creek Cave but did not describe the material. C. lupus has been reported living in the Snake Range in Recent times (Hall 1981) although Man has now reduced its range and numbers considerably.

Vulpes vulpes

Material--Skull with right P1/,2/,4/, left P4/, M2/ (BYUVP 8299), posterior portion of right maxilla with M1/,2/ (BYUVP 7466), partial left maxilla with M1/,2/ (BYUVP 7467), two right C1/'s (BYUVP 7468, 7470), left C1/ (BYUVP 7469), right P4/ (BYUVP 7474), left P4/ (BYUVP 7471), right dentary with M/2 (BYUVP 7461), posterior portion of right dentary with P/4, M/1,/2 (BYUVP 7463), left dentary with M/1,/2 (BYUVP 7464), anterior portion of left dentary with M/1,/2 (BYUVP 7462), right P/4 (BYUVP 7475), left P/4 (BYUVP 7472). An anterior fragment of a right dentary without teeth (BYUVP 7465) and an anterior fragment of a left dentary without teeth (BYUVP 7476) also compare favorably with this species.

Discussion--Vulpes is distinguished from Urocyon by the configuration of the crest on top of the skull and the lack of a prominent "step" on the posteroventral margin of the dentary. The ventral margin of the dentary of Vulpes curves upward posteriorly beginning at the posterior end of the tooth row while in Urocyon it remains uncurved well behind the tooth row all the way to the "step." Urocyon, which ranges from the cave site southward and throughout North America, is intermediate in size between V. vulpes and V. velox. Four of the Crystal Ball Cave specimens include the posterior dentary and lack the "step" characteristic of Urocyon, and all the Crystal Ball Cave specimens are larger than the largest Urocyon specimen examined but compare well in size and shape to V. vulpes.

V. vulpes does not presently occur around Crystal Ball Cave but V. velox and U. cinereoargenteus do (J. C. Bates 1983 personal communication, Hall 1981). The presence of the more northern V. vulpes but not the more southern U. cinereoargenteus in the cave assemblage represents a northward shift of the boundary between these two species. The ranges of V. vulpes and U. cinereoargenteus do overlap to a degree now, but in the western United States the overlap is not great, and where it does occur V. vulpes favors the higher elevations and U. cinereoargenteus the lower elevations (Hall 1981). Based on range maps in Hall (1981), the range of V. vulpes in the western United States is quite scattered, suggesting that it is relectual and that this species is diminishing in numbers there. U. cinereoargenteus has a distinct northern boundary across Utah and Nevada with no remnant populations, suggesting that this species has been making a northward invasion. The Crystal Ball Cave assemblage confirms that U. cinereoargenteus has been expanding its range at the expense of V. vulpes.