Av. 203 65 27 28.1 11.1 19.2 17.7 6.1 6.9 0.8 13.0 6.8
Min. 199 61 26 28.0 10.6 18.9 17.5 5.8 6.6 0.6 12.8 6.6
Max. 206 70 27 28.2 11.6 19.5 17.9 6.4 7.2 1.0 13.2 7.0
----------------------------------------------------------------------
=Thomomys bottae= (Eydoux and Gervais)
_Thomomys bottae_ is a southern species that, within the Great Basin,
reaches the most northern limits of its distribution in Utah. The
animals of this species inhabit the lower valleys, and with the
exception of the Oquirrh Mountains, inhabit also the mountains in that
part of the state west of the central mountain ranges. The specific
characters are: Sphenorbital fissure present; incisive foramina
posterior to infraorbital canal; anterior prism of P4 rounded;
interparietal relatively small; lambdoidal suture straight in region of
interparietal, in Utah specimens.
=Thomomys bottae aureiventris= Hall
_Thomomys perpallidus aureiventris_ Hall, Univ. California
Publ. Zooel., 32:444, July 8, 1930; Univ. California Publ.
Zooel., 37:3, April 10, 1931.
_Thomomys bottae aureiventris_ Goldman, Proc. Biol. Soc.
Washington, 48:156, October 31, 1935.
_Type._--Male, adult, skin and skull, No. 43980, Museum of Vertebrate
Zooelogy, University of California; Fehlman Ranch, 3 mi. N Kelton, 4,225
ft., Box Elder County, Utah; September 27, 1929; collected by Louise
Kellogg; original number 451.
_Range._--Northwestern Utah, and extreme western Utah as far south as
the southern end of the Deep Creek Mountains.
_Diagnosis._--Size medium (see measurements); claws on front feet
small. Color: Near Cinnamon on dorsal and ventral surfaces; inguinal
region, front and hind feet and distal third to half of tail white;
nose, cheeks and postauricular patches grayish black. Skull: Moderately
angular and ridged; zygomatic arches nearly parallel with sides of
skull; jugals vertical; marked thickening at union of jugal and
zygomatic process of maxilla; greatest zygomatic breadth at anterior
part of arches; interpterygoid space lyre-shaped; ventral margin of
jugal concave dorsally; nasals long and denticulate distally; parietal
ridges bowed in at two places, at coronal suture and at middle of
interparietal; paroccipital processes extremely well developed; dorsal
frontomaxillary suture usually straight.
_Comparisons._--From near topotypes of _Thomomys bottae centralis_,
_aureiventris_ differs as follows: Size larger; tail shorter; hind foot
longer; claws on front feet shorter. Color: Slightly darker on upper
parts, but with greater extension of white on ventral surface. Skull:
Zygomatic breadth greater; greatest width across zygomatic arches at
anterior rather than posterior region; zygomatic arches thicker at
union of jugals and zygomatic processes of maxillae; dorsal
frontomaxillary suture less convex medially; mastoid breadth greater;
extension of premaxillae posterior to nasals less; interpterygoid space
lyre-shaped rather than V-shaped.
From topotypes of _Thomomys bottae albicaudatus_, _aureiventris_ can
be distinguished by: Size larger; hind foot longer. Color: Markedly
lighter throughout, Cinnamon as opposed to near (13''''_n_) Black.
Skull: Larger in all but three measurements taken; extension of
premaxillae posterior to nasals less; alveolar length of upper molar
series shorter; zygomatic arches widest anteriorly rather than
posteriorly; thickening at union of jugal and zygomatic process of
maxilla markedly greater; interpterygoid space lyre-shaped as opposed
to V-shaped; lacrimal processes more globose at tips.
_Thomomys bottae aureiventris_ can be readily distinguished from _T. b.
bonnevillei_, _sevieri_, _wahwahensis_, and _convexus_ by larger size
in all measurements taken and darker coloration. The same differences
obtain in comparison with _T. b. tivius_ and _stansburyi_ except that
_aureiventris_ is much lighter colored. See comparisons under those
forms.
_Remarks._--_T. b. aureiventris_ has one of the most extensive ranges
of any race of _T. bottae_ occurring in Utah. The range extends from
the valleys of the northwest corner of the state south along the
extreme western margin of the state approximately to the southern end
of the Deep Creek Mountains. This ascribed range practically bounds the
northwest and western margins of the great salt desert in Box Elder and
Tooele counties. As far as known, this great waste area harbors no
members of the Geomyidae. Pocket gophers were available from four
localities in addition to the type locality. In these four localities
all of the animals were intergrades. The three specimens from Queen of
Sheba Canyon, Deep Creek Mountains, although smaller than
_aureiventris_ in every measurement taken, resemble it in color and
general configuration of the skull. The animals from Trout Creek and
Ibapah at the southern end of the range, although referred to
_aureiventris_, are intermediate between it and _centralis_. In color
and measurements they more closely resemble _centralis_, but the skulls
closely resemble those of _aureiventris_. The skulls show some slight
characteristics of _bonnevillei_, the form to the east, which indicate
an early relationship between the two. Specimens from the east side of
Tecoma Range, adjacent to Pilot Peak, although referred to
_aureiventris_ are intergrades between it and _centralis_. Although
this locality is nearer the type locality of _aureiventris_ than any of
the other record stations, the animals show the maximum departure from
topotypes in morphological features. In color they approach
_centralis_, and agree with it in one-half of the measured characters.
The general configuration of the skull and a majority of the critical
diagnostic characters, for example, jugal thickening, are more nearly
as in _aureiventris_. From the above remarks it is readily understood
that this subspecies is extremely variable.
_Specimens examined._--Total, 55, distributed as follows:
_Box Elder County_: Fehlman Ranch, 3 mi. N Kelton, 4,255
ft., 8 (7, M. V. Z.); Utah-Nevada Boundary, E Side Tecoma
Range, 4,300 ft., 12. _Tooele County_: Ibapah, 5,000 ft.,
21. _Juab County_: Queen of Sheba Canyon, W side Deep Creek
Mountains, 5,600 ft., 11.
=Thomomys bottae robustus= new subspecies
_Type._--Male, adult, skin and skull, No. 2726, Museum of Zooelogy,
University of Utah; Orr's Ranch, Skull Valley, 4,300 ft., Tooele
County, Utah; June 19, 1938; collected by S. D. Durrant; original
number 1583.
_Range._--Skull Valley, Tooele County, Utah.
_Diagnosis._--Size medium (see measurements); tail short; hind foot
short. Color: In a series of 24 animals, upper parts vary from Pale
Smoke Gray (4 specimens) through Cinnamon Buff (19 specimens) to Dark
Mouse Gray (1 specimen). The Cinnamon Buff color is considered to be
typical. Color grading to lighter on underparts; postauricular patches
small and grayish black; front and hind feet and distal part of tail
white. Skull: Small, flat and heavily ridged; nasals short; zygomatic
arches heavy and widely spreading, widest posteriorly at union of jugal
and squamosal; union of jugal and zygomatic process of maxilla
thickened, with a ventrally directed spinous process in sixty percent
of the specimens; occasionally there is a second process, also directed
ventrally at union of jugal and zygomatic process of squamosal;
zygomatic arches convex dorsally; deep dorsal depression present in
frontal bones in mature specimens; lacrimal processes prominent,
projecting well above the arch at the anteromedial angle of the orbit;
interpterygoid spaces V-shaped; tympanic bullae well inflated
ventrally; upper incisors short, and pale; when placed on a flat plane
the dorsal surface of the skull is nearly parallel to the substratum;
space enclosed within the zygomatic arches nearly quadrangular.
_Comparisons._--From topotypes of _Thomomys bottae aureiventris_,
_robustus_ can be distinguished as follows: Size smaller; tail and hind
foot shorter. Color: Lighter throughout. Skull: Smaller, more heavily
ridged and more nearly flat; nasals shorter; rostrum relatively wider
and shorter; zygomatic arches shorter and relatively more widely
spreading with greatest width posteriorly as opposed to anteriorly;
junction of jugal and zygomatic process of maxilla not as prominent;
_aureiventris_ shows no spinous process at this junction; lacrimal
processes larger and projecting farther dorsally; enclosed space within
zygomatic arches roughly quadrangular as opposed to triangular;
mastoidal part of tympanic bullae less exposed; sphenorbital fissure
smaller; interpterygoid space V-shaped rather than lyre-shaped; palatal
pits smaller and shallower; tympanic bullae smaller, but more inflated
ventrally; basioccipital averaging relatively wider; molars smaller;
upper incisors shorter, smaller and cadmium yellow as opposed to orange
yellow.
Comparisons of _robustus_ with topotypes of _Thomomys bottae
albicaudatus_ show the following: Size smaller. Color: Lighter
throughout; postauricular patches smaller and lighter. Skull: Smaller,
more compact and more nearly flat; rostrum shorter and more nearly
straight; lacrimal processes larger, projecting higher above the
anteromedial angle of the orbit; parietal ridges uniformly heavier;
mastoid width actually as well as relatively wider; zygomatic arches
heavier and relatively much wider (males 76.2 percent of basilar
length, females 73.8 percent as opposed to males 73.8 percent and
females 73.5 percent); union of jugal and zygomatic process of maxilla
uniformly more thickened; spinous process at jugal-maxillary suture
present; zygomatic arches much more concave on ventral surface; uniform
deep depression present in mature adults, between frontal processes of
premaxillae, and anterior interorbital region of frontals; extension of
premaxillae posterior to nasals less; sphenorbital fissure more
constricted; tympanic bullae more inflated ventrally, extending well
ventrad of basioccipital; palatal pits shallower and smaller; molars
smaller; upper incisors shorter, narrower and paler (see comparison of
_aureiventris_).
From near topotypes of _Thomomys bottae centralis_ from 1 mile east of
Garrison, Millard County, Utah, _robustus_ differs in: Size smaller;
tail and hind foot shorter. Color: Lighter, terminal bands of hair
cinnamon, but because more black in underfur the animals appear darker;
postauricular patches smaller and lighter. Skull: Shorter, more nearly
flat and much more heavily ridged; nasals shorter; rostrum shorter and
wider; lacrimal processes larger and projecting higher above
anteromedial angle of orbit; zygomatic arches heavier, shorter, more
angular and actually as well as relatively wider; jugals thicker; angle
between maxillary plate and rostrum less obtuse; spinous process at
jugal-maxillary suture present; extension of premaxillae posterior to
nasals less; parietal ridges much more pronounced; looked at from
above, space enclosed within zygomatic arches more quadrangular in
shape as opposed to roughly triangular; tympanic bullae more inflated
ventrally; molars smaller; upper incisors shorter, narrower and paler.
The characters that distinguish _robustus_ from topotypes of _Thomomys
bottae wahwahensis_ are: Size slightly smaller. Color: Darker
throughout. Skull: Rostrum longer and narrower; nasals longer;
zygomatic arches wider and longer; lacrimal processes larger and
projecting higher above anteromedial angle of the orbit; parietal
ridges more roughened; tympanic bullae much larger and more inflated
ventrally; supraoccipital higher; middorsal depression in frontals
present. For comparisons with _Thomomys bottae bonnevillei_ see account
of that form.
The remaining forms from the Bonneville Basin, namely, _Thomomys bottae
sevieri_, _convexus_, _tivius_ and _stansburyi_ are all easily
distinguished from _robustus_. Specimens of _sevieri_ are paler,
smaller in every measurement taken, and the skulls are weaker and less
angular. All specimens of _convexus_ are paler, the skulls are more
convex dorsally and narrower, with less ridging and angularity. Both
_tivius_ and _stansburyi_ are small dark forms, with weak, smooth,
small skulls as compared with _robustus_ which is light colored and has
compact, ridged and angular skulls.
_Remarks._--Twenty-three specimens were obtained at a small isolated
spring. Critical study of animals taken only a few miles to the east
prove them to be so different as to be referable to another subspecies,
_albicaudatus_. _T. b. robustus_ is an endemic form in this desert
valley. The variable color is noteworthy but difficult to explain in an
isolated population as small as this one. All five of the gray animals
are females of which four are lactating adults. The affinities of this
subspecies are with _albicaudatus_ to the east, but enough time has
elapsed since isolation to enable them to differentiate.
_Specimens examined._--Total, 23, from the type locality.
=Thomomys bottae minimus= Durrant
_Thomomys bottae minimus_ Durrant, Proc. Biol. Soc.
Washington, 52:161, October 11, 1939; Marshall, Journ.
Mamm., 21:154, May 14, 1940.
_Type._--Male, adult, skin and skull, No. 263942, U. S. National Museum
(Biological Surveys Collection); Stansbury Island, Great Salt Lake,
Tooele County, Utah; June 25, 1938; collected by William H. Marshall;
original number 141.
_Range._--Known only from the type locality.
_Diagnosis._--Size small (see measurements); tail relatively long.
Color: Upper parts Pinkish Buff, darker on head; underparts Pale
Pinkish Buff; front and hind feet white; nose, chin and postauricular
patches black. Skull: Long, slender and nearly devoid of ridges;
braincase moderately inflated; interparietal quadrangular; zygomatic
arches weak, widest in temporal region, but neither widely spreading
nor angular; nasals straight and truncate posteriorly; extension of
premaxillae posterior to nasals relatively great; tympanic bullae
moderately inflated; palatal pits deep; rostrum short but narrow;
interpterygoid space moderately lyre-shaped; upper incisors narrow;
molars light.
_Comparisons._--Compared with topotypes of _Thomomys bottae
albicaudatus_, _minimus_ differs as follows: Size markedly smaller;
claws on front feet shorter and weaker. Color: Markedly lighter
throughout, being Pinkish Buff as contrasted with near (13''''_n_)
Black. Skull: Smaller in every measurement taken; slender, smooth, weak
and nonangular as opposed to ridged, robust, wide and angular;
zygomatic arches much weaker and not so widely spreading posteriorly;
ascending processes of premaxillae much narrower; extension of
premaxillae posterior to nasals less; interpterygoid space moderately
lyre-shaped as opposed to V-shaped; dentition lighter.
Topotypes of _minimus_ differ from those of _Thomomys bottae
aureiventris_ as follows: Size markedly smaller. Color: Lighter
dorsally and no "gold color" on underparts. Skull: Markedly smaller in
every measurement taken; weak, smooth and slender as opposed to ridged,
angular and robust; zygomatic arches weak and widest posteriorly rather
than heavy and widest anteriorly; no great thickening at region of
union of jugal and zygomatic process of the maxilla; jugals more nearly
straight rather than concave laterally; interpterygoid space not so
markedly lyre-shaped; dentition lighter.
The races nearest geographically to _minimus_ are _Thomomys bottae
nesophilus_ and _T. b. stansburyi_. For comparisons see accounts of
those forms.
_Remarks._--This subspecies is the smallest of all the races of
_Thomomys bottae_ occurring in Utah. As far as known it is endemic to
Stansbury Island, and since the Pleistocene Lake Bonneville attained
its highest level has remained on that part of Stansbury Island that
was above this high level. (See comments under _nesophilus_.) The sandy
nature of the soil and the desert conditions of the area that has since
been exposed at lower levels apparently do not constitute a favorable
environment. Unlike _nesophilus_ from Antelope Island, this form does
not have its affinities with _albicaudatus_, the valley form of the
adjacent mainland, but does show affinities with _stansburyi_, the
nearest mountain form on the mainland. This is easily understood when
one realizes that Stansbury Island is only an isolated part of
Stansbury Mountain that projects northward as a peninsula into Great
Salt Lake. The history of Stansbury Island with reference to isolation
of _minimus_ parallels that of _nesophilus_ on Antelope Island. See
discussion under _nesophilus_.
_Specimens examined._--Total, 5, as follows: _Tooele
County_: Stansbury Island, Great Salt Lake, 5 (U. S. N. M.).
=Thomomys bottae nesophilus= Durrant
_Thomomys bottae nesophilus_ Durrant, Bull. Univ. Utah, 27
(No. 2):2, October, 1936; Marshall, Journ. Mamm., 21:156,
May 14, 1940.
_Type._--Male, adult, skin and skull, No. 1136, Museum of Zooelogy,
University of Utah; Antelope Island, Great Salt Lake, Davis County,
Utah; April 20, 1935; collected by S. D. Durrant; original number 761.
_Range._--Known only from the type locality.
_Diagnosis._--Size medium (see measurements); claws on front feet long.
Color: Upper parts Cinnamon Buff; lighter below; sides Pinkish Buff
interspersed with gray; pectoral and inguinal regions Cinnamon; nose
grayish black; postauricular patches black. Skull: Interparietal
wedge-shaped; tympanic bullae small; dorsal surface of lambdoidal
prominence 3 mm. wide rather than developed as a crest; jugals nearly
straight; zygomatic arches strongly rectangular.
_Comparisons._--Compared with topotypes of _Thomomys bottae
albicaudatus_, _nesophilus_ is of approximately the same size, but
differs as follows: Claws on front feet longer. Color: Lighter
throughout; tail white terminally, but much darker at base;
postauricular patches smaller. Skull: Interparietal wedge-shaped as
opposed to roughly quadrangular; lambdoidal eminence more of a crest
than a ridge; tympanic bullae smaller; jugals more nearly straight;
zygomatic arches more nearly rectangular.
From topotypes of _Thomomys bottae aureiventris_, _nesophilus_ differs
in: Size smaller; claws on front feet longer. Color: Darker throughout;
postauricular patches larger. Skull: Heavier, more massive; zygomatic
arches more robust and convex laterally rather than concave;
interparietal wedge-shaped rather than roughly quadrangular; braincase
more nearly flat; tympanic bullae markedly smaller; upper molariform
series longer; molariform teeth wider and heavier; interpterygoid space
V-shaped rather than lyre-shaped.
The race nearest geographically to _nesophilus_ is _T. b. minimus_ from
Stansbury Island, Great Salt Lake. It can easily be distinguished from
_minimus_ by the following features: Size much larger; claws on front
feet longer and thicker. Color: Darker throughout; postauricular
patches larger and with more admixture of buff colored hairs. Skull:
Larger in every measurement taken; wide and robust as opposed to narrow
and slender; zygomatic arches more widely spreading and angular;
braincase more nearly flat; tympanic bullae actually larger, but
relatively smaller; lambdoidal eminence flat-topped rather than a
crest; interparietal wedge-shaped as opposed to quadrangular; teeth
larger.
_Remarks._--The affinities of _nesophilus_ of Antelope Island are
unquestionably with _albicaudatus_ of the eastern and southern
mainland. At the time of this writing (1945), Antelope Island is not
truly an island, but only the tip of a broad peninsula projecting
westward into Great Salt Lake. Nevertheless, the area of occurrence of
_nesophilus_ is effectively isolated by the exposed, sandy lake bottom
that is unsuited to occupancy by pocket gophers. Fluctuations in the
level of the Great Salt Lake have broken and reestablished this
connection with the mainland many times. Each of the several other
kinds of mammals which are known from both the island and the mainland
show no differentiation on the island. These are kinds (see Marshall,
1940:156), which more freely cross the exposed, sandy lake bottom. I,
myself, have noted tracks of coyotes going to and from the island. The
pocket gopher, _nesophilus_, so far as known is the only mammal which
has developed a subspecies endemic to the island. The beach levels of
Pleistocene Lake Bonneville are well marked on both Antelope Island and
Stansbury Island, which is fifteen miles west of Antelope Island. On
the eastern side of Antelope Island the lower beach levels of this
prehistoric lake are farmed. Although sought for elsewhere on this
island, pocket gophers were found only in the farmed land. On Stansbury
Island there has been no farming, and the endemic pocket gophers,
_minimus_, although sought for elsewhere on that island were found only
above the highest beach levels of the ancient lake. Evidently these
pocket gophers still occupy only that part of Stansbury Island that
projected above water during the greatest height of Lake Bonneville.
Farming on Antelope Island may have developed a more favorable
environment for pocket gophers, thus causing them to move down to the
lower levels from that part of the island that was above water during
Pleistocene times.
_Specimens examined._--Total, 5, from the type locality.
=Thomomys bottae stansburyi= new subspecies
_Type._--Female, adult, skin and skull, No. 2045, Museum of Zooelogy,
University of Utah; South Willow Creek, Stansbury Mountains, 7,500 ft.,
Tooele County, Utah; July 2, 1937; collected by O. S. Walsh and S. D.
Durrant; original number 1257 of Durrant.
_Range._--Stansbury Mountains, Tooele County, Utah.
_Diagnosis._--Size small (see measurements). Color: Upper parts
Saccardo's Umber, darker on head; sides and underparts Pinkish Buff;
nose, chin and postauricular patches black; front and hind feet and
distal third to half of tail white. Skull: Small, slender, weak and
smooth; zygomatic arches light and not widely spreading; zygomatic
arches actually as well as relatively short; interparietal generally
quadrangular; nasals relatively long and slender; interpterygoid space
narrowly V-shaped; basioccipital fairly wide; tympanic bullae
moderately inflated ventrally; dentition light.
_Comparisons._--Topotypical specimens of _stansburyi_ can be readily
distinguished from those of _Thomomys bottae centralis_, _aureiventris_
and _albicaudatus_ by being smaller in every measurement taken,
particularly those of the skull; the skull is weaker and smoother. In
color _stansburyi_ is like _albicaudatus_ but is much darker throughout
than _aureiventris_ and _centralis_.
Comparisons of topotypes of _stansburyi_ with those of _Thomomys bottae
sevieri_ show them to be of approximately the same size, but to differ
as follows: Color: Darker throughout. Skull: Zygomatic arches shorter;
tympanic bullae less inflated ventrally; zygomatic breadth less;
mastoid breadth greater; width across alveolar processes of maxillae
greater; alveolar length of upper molar series greater; molariform
teeth larger.
Compared with topotypes of _Thomomys bottae minimus_, _stansburyi_ is
seen to be of larger size and darker color throughout, with a skull
that is larger in most every measurement taken, although of the same
slender, smooth, nonangular type.