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UNIVERSITY OF KANSAS PUBLICATIONS
MUSEUM OF NATURAL HISTORY

Volume 9, No. 21, pp. 539-548
January 14, 1960




Pleistocene Pocket Gophers
From San Josecito Cave,
Nuevo León, México

BY

ROBERT J. RUSSELL


UNIVERSITY OF KANSAS
LAWRENCE
1960


UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
Robert W. Wilson

Volume 9, No. 21, pp. 539-548
Published January 14, 1960


UNIVERSITY OF KANSAS
Lawrence, Kansas


PRINTED IN
THE STATE PRINTING PLANT
TOPEKA, KANSAS
1960

[Illustration]

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Pleistocene Pocket Gophers From San Josecito Cave, Nuevo León, México

BY

ROBERT J. RUSSELL


Cueva de San Josecito in the province of Aramberri, near the town on
Aramberri, Nuevo León, México, is at an elevation of approximately 7400
feet above sea level on the east-facing slope of the Sierra Madre
Occidental in a limestone scarp. The dominant vegetation about the cave
is the decidedly boreal forest association of pine and live oak.
Additional information concerning the cave is provided by Miller
(1943:143-144).

Animal remains recovered from San Josecito Cave are among the most
important Pleistocene finds in México, and include the most extensive
collection of Pleistocene geomyids. The vertebrate remains are probably
late Pleistocene in age; certainly they are post-Blancan, since the
genera _Equus_, _Preptoceras_, _Smilodon_, and _Aenocyon_ (all
Pleistocene genera) are present. According to Miller's (_loc. cit._:145)
extensive report on the avifauna, the bird remains from the cave are a
remarkable assemblage and beautifully preserved. Most of the mammalian
remains have been studied in detail, and the results of these studies
have been published in a number of papers each treating specific groups.
These reports provide valuable information concerning the distribution
of mammals in northeastern México in the late Pleistocene, a knowledge
of which is most important to an understanding of present patterns of
distribution and evolution of Mexican mammals.

Cushing's (1945:182-185) report on his study of the rodents and
lagomorphs includes a description of an extinct pygmy species of rabbit,
_Sylvilagus leonensis_. He records three kinds of pocket gophers from
San Josecito; Cushing was able to separate the genus Thomomys from two
unidentified geomyids (_loc. cit._:185). These prove to belong to the
genera _Cratogeomys_ and _Heterogeomys_; the materials are described
below. Cushing records also larger mammals, including the antilocaprid
(_Stockoceros conklingi_), saber-toothed cat (_Smilodon_), dire wolf
(_Aenocyon_), a large oviboid (_Preptoceras_), and deer (_loc.
cit._:182).

More recently Findley (1953:633-639) has written on the remains of the
family Soricidae taken from the cave, and Hooper (1952:59) has studied
the bones of the genus _Reithrodontomys_ and found them not different
from those of _R. megalotis_ that inhabits the region of the cave today.
Handley (1955:48) has described a new species of plecotine bat,
_Corynorhinus tetralophodon_, from the collection. Jones (1958:389-396)
published an account of the bats of San Josecito, and described a new
vampire bat, _Desmodus stocki_, from the cave. Jakway (1958:313-327) has
reported on the lagomorphs and rodents in detail, and compared this part
of the cave fauna with that of Rancho La Brea and Papago Spring Cave,
Arizona. Jakway (_lit. cit._:323-324) suggests that the fauna from San
Josecito is late Pleistocene, probably contemporaneous with the remains
from Papago Spring Cave and pre-Rancholabrean.

   I thank Professor E. Raymond Hall and Dr. Robert W. Wilson for
   their permission to examine this material and for critical comments
   and advice on the manuscript. The drawings were made by Miss Lucy
   Remple. The specimens are a part of the collection of fossil
   vertebrates formerly belonging to the California Institute of
   Technology, but now the property of the Los Angeles County Museum.
   The specimens had been lent by the late Professor Chester Stock to
   Professor Hall and Dr. Wilson for study and report. All
   measurements herein are in millimeters.


#Thomomys umbrinus# (Richardson)

Material referable to _Thomomys_ consists of a nearly complete cranium,
L.A.C.M. (C.I.T.) No. 3952, with nasals, maxillary teeth, and lower
parts of braincase missing and zygomata broken; four rami (unnumbered),
one of which is badly broken; and two isolated molariform teeth. The
skull has a sphenoidal fissure, a feature typical of the _umbrinus_
group of _Thomomys_. The fossil specimens closely approximate in size
the living subspecies _Thomomys umbrinus analogus_ Goldman. _Thomomys_
is not known from the vicinity of the cave at the present time and has
not been reported from southwestern Nuevo León, even though there has
been extensive collecting for pocket gophers there in recent years. To
my knowledge the nearest record of occurrence of modern _Thomomys_ is a
series of _Thomomys umbrinus analogus_ from 12 miles east of San Antonio
de las Alazanas at an elevation of 9000 feet in the state of Coahuila
(Baker, 1953:511), approximately 85 miles to the northwest. The fossil
gophers are not from the talus of the cave floor, which is evidently of
subrecent origin, but from the Pleistocene deposits below. Close
resemblance to the living subspecies _T. u. analogus_, however,
indicates that these remains are not so old as some of the other geomyid
fossils from the cave.


#Cratogeomys castanops# (Baird)

Seven rami pertain to the genus _Cratogeomys_. All except three,
L.A.C.M. (C.I.T.) Nos. 2974, 2978, and 3954, lack cheek teeth and the
posterior processes are missing on most of the mandibles. No. 2974 is
smaller than the other specimens, and probably is from a young
individual. No. 3954 may have been fossilized at an earlier date than
the other six jaws; however, it is comparable to them in size and
morphology. Also present in the deposits are three limb bones of
_Cratogeomys castanops_. One, a right humerus bearing L.A.C.M. (C.I.T.)
No. 2982, is slightly larger than that of the pocket gophers living in
the area now. Two tibias, L.A.C.M. (C.I.T.) Nos. 2983 and 2984, complete
the material referable to this species.

_Cratogeomys castanops planifrons_ (see Russell and Baker, 1955:607)
occurs in the immediate vicinity of San Josecito today. None of the rami
from the cave differs appreciably from those of the _subnubilus_ group
of _Cratogeomys castanops_, a group of small subspecies including
_planifrons_, _subnubilus_, _rubellus_ and _peridoneus_. All are small
in external measurements and skull and differ markedly in this respect
from the group of large subspecies (the _subsimus_ group) that occurs
farther northward in Coahuila and Nuevo León.


#Cratogeomys# sp.

A rostral part of a skull, L.A.C.M. (C.I.T.) No. 2927, is referable to
the genus _Cratogeomys_. This fragment consists of the anterior part of
the skull, including a portion of the frontals, the premaxillae, a small
part of the left maxilla, and the anterior parts of the palatines. The
nasals are missing, but both incisors are in place including most of the
roots. The single median sulcus on the anterior face of each incisor is
typical of the genus _Cratogeomys_. The rostrum is long (25.8), as great
in length as in the largest subspecies of the _subsimus_ group of
_Cratogeomys castanops_ (see previous account for explanation) and as
long as the rostrum of _Cratogeomys perotensis_ which is now known only
from Veracruz, México. The length of the rostrum was measured from the
most anterior median projection of the premaxillary to the most
posterior dorsal projection of the same bone. Actually, and especially
in relation to its length, the rostrum of the fossil is remarkably
narrow. The breadth of the rostrum measures 10.4, which is comparable to
that in the _subnubilus_ group of small subspecies, and less than that
(11.4 in the smaller adult females to 13.7 in the larger adult males) in
the _subsimus_ group of large subspecies. The breadth of rostrum in the
fossil is 40.3 per cent of the length of the rostrum. In living
_Cratogeomys castanops_ (both the large and small subspecies groups, and
including both females and males) the breadth of rostrum amounts to
between 44.0 and 51.4 per cent of its length. The rostrum in
_Cratogeomys perotensis_ (and in other species of the _merriami_ group)
is relatively much broader than in _Cratogeomys castanops_. Even though
the rostrum of the fossil is narrower than in Recent species of
_Cratogeomys_, the ventral border in the area of the palatine slits is
more heavily constructed than in any of the living species, and it is
nearly parallel-sided rather than tapered toward the midline anteriorly.
At the lateral edge of the enamel plate of the incisors there is a
distinct shelf, a characteristic of the _merriami_ group of species and
a feature not well developed in _Cratogeomys castanops_.

I hestitate to refer this fragment to any of the living species,
although I would judge it to represent a form closer to the species
_castanops_ than to the _merriami_ group (_C. perotensis_). The rostrum
may represent, and probably does, an undescribed and extinct species of
_Cratogeomys_, but in my opinion it should not be given formal taxonomic
status until more adequate material is available.

If the fossil is actually _Cratogeomys castanops_, and if the fragment
is from an earlier deposit in the cave than is the material here
assigned to _Cratogeomys castanops_, the fossil stock could be ancestral
to the group of small subspecies provided there had been a trend in
evolution toward smaller size. Another possibility is that a shift in
geographic range of the kinds of _Cratogeomys_ that lived in the
vicinity of the cave has occurred, and that the fossil represents an
evolutionary line with no close relationship to Recent species and now
is extinct. Additional material is needed before the history of these
species can be reconstructed with validity.


#Heterogeomys onerosus# new species

   _Holotype._--Los Angeles County Museum (C.I.T.) No. 2384, an
   incomplete left ramus, bearing incisor and p4; the alveolus of
   m1-m3 is present (Fig. 1a). Paratypes: Two isolated and unnumbered
   right upper incisors, one isolated premolar, and five additional
   rami, Nos. 2385, 2386, 2388, and two with no number.

   _Horizon and type locality._--Upper Pleistocene, Cueva de San
   Josecito, province of Aramberri, near the town of Aramberri, Nuevo
   León, México; California Institute of Technology, Vertebrate
   Paleontology Locality 192.

_Description of Holotype._--Differs from any known living species of
_Heterogeomys_, by the significantly heavier and deeper ramus (see Table
1 and Fig. 1). The holotype is compared with the largest adult male of
_Heterogeomys hispidus_ (_H. torridus_ is smaller than _hispidus_)
available to me in Table 1. Relative to the length of the ramus
(measured from the anterior mental foramen to the posterior margin of
the capsule that surrounds the root of the lower incisor), the depth of
the ramus anterior to the molariform tooth-row is 33.0 per cent in _H.
onerosus_ compared with 27.3 per cent in _H. hispidus_. If the fossil
ramus is that of a female (females are significantly smaller than males
in _Heterogeomys_) then the differences would be greater than recorded.

TABLE 1. DEPTH OF MANDIBULAR RAMUS

A: Least depth in front of premolar
   (See A to A' on Fig. 1c)
B: Depth of ramus opposite re-entrant angle of p4
   (B to B' on Fig. 1c)
C: Depth from a point in front of capsule for incisor
   (See C to C' on Fig. 1c)

=====================================+======+======+======
                                     |  A   |  B   |  C
-------------------------------------+------+------+------
_H. onerosus_ holotype               | 11.0 | 17.4 | 11.7
-------------------------------------+------+------+------
_H. h. hispidus_ [Male] ad., 23979 KU|  9.1 | 15.2 | 10.5
-------------------------------------+------+------+------

The angle between the anterior border of the coronoid process and the
dorsal border of the ramus of the mandible is more acute, and the
posteroventral margin of the ramus is more nearly straight, in
_onerosus_ than in _hispidus_. The molariform tooth-row in _onerosus_ is
only slightly longer (13.9 in contrast to 13.5) than in _hispidus_ and
_torridus_. The ventral border of the massenteric ridge is weakly
developed in _onerosus_ and hardly discernable whereas in the living
species of _Heterogeomys_ the massenteric ridge is strongly developed
posteriorly forming a noticeable prominence.

_Description of Paratypes._--The fossils are referable to the genus
_Heterogeomys_ on the basis of the short lateral angular processes of
the lower jaw and on the basis of the associated upper incisors, which
have a single distinct sulcus that lies toward the inner margin of each
tooth. The isolated lower premolar that is referred to the new species
is as large as that of the holotype and has the enamel pattern of
_Heterogeomys_.

[Illustration: Figs. 1a-1c. × 1-1/2

FIG. 1a. _Heterogeomys onerosus_, lateral view of left lower jaw of
holotype.

FIG. 1b. _Heterogeomys onerosus_, front view of right, upper incisor.

FIG. 1c. _Heterogeomys hispidus_, lateral view of left lower jaw, No.
23979, [Male] adult, from 3 km. E San Andrés Tuxtla, Veracruz.]

One jaw fragment, L.A.C.M. (C.I.T.) No. 2368, is smaller than the others
and probably is from a young individual. Two others L.A.C.M. (C.I.T.)
No. 2384 and one unnumbered, are smaller than the holotype, and possibly
are the remains of females; however, they have the same characteristic
shape as the holotype. Nevertheless, the two rami mentioned above are
significantly larger than in adult males of modern _Heterogeomys_ and
are especially larger than in females. Another jaw fragment, L.A.C.M.
(C.I.T.) No. 2385, is seemingly as large as, or perhaps larger than,
the holotype, although the posterior part of the ramus behind the
alveolus of m2 is missing. An additional unnumbered ramus is of somewhat
lighter construction than the holotype, but is important since it bears
not only the incisor and p4 but also the first two lower molars. The
only other material referable to _Heterogeomys onerosus_ is a
fragmentary and isolated lower molar tooth that has a single posterior
enamel blade, a feature characteristic of a number of Recent genera of
pocket gophers, and some limb bones which are slightly larger than
corresponding elements in Recent species of _Heterogeomys_.

_Remarks._--Pocket gophers do not inhabit caves; therefore gophers were
brought into the cavern probably by birds of prey, the remains of which
were common in the deposits (Miller, 1943:152-156), or conceivably by
carnivorous mammals. Since most of the raptorial predators that would
prey on pocket gophers do not have a wide hunting territory, it is
likely that the gophers were taken within a short distance of the cave.
The presence of the genus _Heterogeomys_ in the deposits strongly
suggests a tropical situation in the vicinity of the cave when these
gophers were taken, because the distribution of this genus today is
entirely within the Tropical Life-zone.

Since the presumably early time when tropical conditions, or more nearly
tropical conditions, prevailed at San Josecito Cave, climatic shifts
account for a humid boreal environment there and its associated fauna.
Findley (_lit. cit._:635-636) reports from San Josecito the remains of
the boreal shrew _Sorex cinereus_ that today occurs no nearer than 800
miles to the northward in the mountains of north-central New Mexico. As
he points out, that species requires hydric communities of cool
climates, and in the Wisconsin Glacial age such climates probably
prevailed in the high mountainous region where San Josecito is located.
Since the time when a more mesic boreal environment occurred at San
Josecito, climatic shifts have favored more xeric conditions as are
found in the vicinity of the cave today. The more arid environments
would support the occurrence of _Cratogeomys_ and _Thomomys_; however
the ecological affinities of the fragment here referred to _Cratogeomys_
sp. are unknown.

The more nearly tropical environment there could have occurred either
during a Wisconsin interglacial period or during the Sangamon
Interglacial age. _Heterogeomys onerosus_ perhaps lived near the cave
during an interglacial period; since then it became extinct or evolved
into the Recent species _Heterogeomys hispidus_. _Heterogeomys_ has not
previously been recorded from Pleistocene or earlier deposits.


LITERATURE CITED

BAKER, R. H.

  1953. The pocket gophers (genus Thomomys) of Coahuila, México.
        Univ. Kansas Publ., Mus. Nat. Hist., 5:499-514, 1 fig. in
        text, June 1.

CUSHING, J. E., JR.

  1945. Quaternary rodents and lagomorphs of San Josecito Cave, Nuevo
        León, México. Jour. Mamm., 26:182-185, July 19.

FINDLEY, J. S.

  1953. Pleistocene Soricidae from San Josecito Cave, Nuevo León,
        México. Univ. Kansas Publ., Mus. Nat. Hist., 5:633-639,
        December 1.

HANDLEY, C. O., JR.

  1955. _A new Pleistocene bat (_Corynorhinus_) from México._ Jour.
        Washington Acad. Sci., 45:48-49, March 14.

HOOPER, E. T.

  1952. A systematic review of the harvest mice (genus
        _Reithrodontomys_) of Latin America. Miscl. Publ. Mus. Zool.,
        Univ. Michigan, 77:1-255, 9 pls., 24 figs., 12 maps, January
        16.

JAKWAY, G. E.

  1958. Pleistocene Lagomorpha and Rodentia from the San Josecito
        Cave, Nuevo León, México. Trans. Kansas Acad. Sci.,
        61:313-327, November 21.

JONES, J. K., JR.

  1958. Pleistocene bats from San Josecito Cave, Nuevo León, México.
        Univ. Kansas Publ., Mus. Nat. Hist., 9:389-396, 4 figs.,
        December 19.

MILLER, L.

  1943. The Pleistocene birds of San Josecito Cavern, México. Univ.
        California Publ. Zool., 47:143-168, April 20.

RUSSELL, R. J., and BAKER, R. H.

  1955. Geographic variation in the pocket gopher, Cratogeomys
        cantanops, in Coahuila, México. Univ. Kansas Publ., Mus. Nat.
        Hist., 7:591-608, 1 fig., March 15.


_Transmitted October 28, 1959._


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