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Title: Pleistocene Soricidae from San Josecito Cave, Nuevo Leon, Mexico
Author: Findley, James S.
Language: English
As this book started as an ASCII text book there are no pictures available.
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Pleistocene Soricidae from San Josecito Cave,
Nuevo Leon, Mexico

BY

JAMES S. FINDLEY


University of Kansas Publications
Museum of Natural History

Volume 5, No. 36, pp. 633-639
December 1, 1953


University of Kansas
LAWRENCE
1953



UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, A. Byron Leonard,
Robert W. Wilson

Volume 5, No. 36, pp. 633-639
December 1, 1953


UNIVERSITY OF KANSAS
Lawrence, Kansas


PRINTED BY
FERD VOILAND, JR., STATE PRINTER
TOPEKA, KANSAS
1953

25-265



Pleistocene Soricidae from San Josecito Cave,
Nuevo Leon, Mexico

By

JAMES S. FINDLEY


Bones of a large number of vertebrates of Pleistocene age have been
removed from San Josecito Cave near Aramberri, Nuevo León, México.
These bones have been reported upon in part by Stock (1942) and Cushing
(1945). A part of this material, on loan to the University of Kansas
from the California Institute of Technology, contains 26 rami and one
rostrum of soricid insectivores. Nothing seems to be known of the
Pleistocene Soricidae of México. The workers cited do not mention them
and no shrews are listed by Maldonado-Koerdell (1948) in his catalog of
the Quaternary mammals of México. Comparison of these specimens with
pertinent Recent material from México, the United States, and Canada
leads me to the conclusion that they represent two genera and at least
three species. The material examined is described below.


Sorex cinereus Kerr

One right ramus, bearing all three molars but lacking the other teeth
and the tip of the coronoid process, needs close comparison only with
certain of the smaller North American species of _Sorex_. From _S.
merriami_ of southeastern Wyoming, it differs in having a shorter, much
shallower dentary, a shorter molar row, and a lower coronoid. In every
particular it is identical with _Sorex cinereus_. _Sorex cinereus_ from
northern British Columbia and the specimen from Nuevo León differ from
_Sorex saussurei_, _S. obscurus_, and _S. vagrans_ in the ratio of the
height of the coronoid to the length of the dentary. This ratio
averages 49.6% in _S. cinereus_ and 53.0% or more (up to 60.0%) in the
other species. _Microsorex hoyi_ differs from _S. cinereus_ and from
the specimen in question in deeper and shorter dentary, more robust
condyle, dentary less bowed dorsally, molars shorter in anteroposterior
diameter and higher in proportion to this dimension.

This record, as far as I can determine, constitutes a southward
extension of the known Pleistocene or Recent range of this species of
approximately 800 miles. The nearest known occurrence of _S. cinereus_
in Recent times is in the mountains of north-central New Mexico. The
species now has an extensive range in boreal North America and prefers
mesic and hydric communities from which it rarely wanders. I know of no
instance of the occurrence of the cinereous shrew in desert areas such
as there are between many of the mountain ranges of southern New
Mexico, Coahuila, and Nuevo León. Therefore, unless the habitat
preferences of the species have changed since Pleistocene times, this
find constitutes additional evidence that more humid conditions at one
time prevailed in the regions mentioned.


Sorex saussurei Merriam

Fragments of three other specimens of _Sorex_ occur in the collection.
One of these is a right ramus, C. I. T. No. 3943, and is complete
except for the canine. The other two bear no numbers and I have
designated them "A" and "B." "A" is a left ramus with the dentary
broken off anterior to the canine and bears p4 and the canine. "B" is a
right ramus bearing m2 and the roots of m3 and is broken off at the
middle of the alveolus of m1. Each specimen has certain peculiarities
but they resemble one another so closely that I regard all three as of
the same species. The teeth, where comparable, are of essentially the
same size and configuration. The horizontal rami of the dentaries are
the same. The fossils differ, however, in the configuration of the
coronoid process. In No. 3943 the coronoid is robust and inclined
anteriorly with respect to a line drawn perpendicular to the dentary.
The posterointernal ramal fossa (see Hibbard, 1953) is deeply excavated
with a distinct superior border approximately halfway between its
inferior border and the top of the coronoid. In addition to the
mandibular foramen there is a small foramen immediately posterior to it
opening into the posterointernal ramal fossa. I shall refer to this as
the post-mandibular foramen. The tip of the coronoid is broad, not
tapering, and quadrate, and its entire superior border is inclined
rather sharply medially. Specimen "B" differs from No. 3943 in that the
posterointernal ramal fossa extends nearly to the tip of the coronoid,
which is narrower toward the tip and somewhat tapered dorsally. The
post-mandibular foramen is large and the opening of the mandibular
canal is within the posterointernal ramal fossa. In addition the
coronoid does not incline anteriorly. Specimen "A" is intermediate
between No. 3943 and "B" in the characters mentioned and differs from
both in that the post-mandibular foramen is widely separated from the
mandibular foramen.

Comparison of the Pleistocene specimens with specimens of Recent
species of North American _Sorex_ reveals that the presence or absence
of the post-mandibular foramen is almost constant in any one species.
In possessing this foramen the fossils differ from most individuals of
the species: _Sorex cinereus_, _S. pacificus_, _S. milleri_, _S.
vagrans_, _S. obscurus_, _S. ornatus_, _S. fumeus_, _S. palustris_, _S.
bendirii_, and _S. veraepacis_. The fossils differ from all these
species in other characters as well; consequently detailed comparisons
with them need not be made here. Species which possess the
post-mandibular foramen include _Sorex saussurei_, _S. merriami_, _S.
trowbridgii_, _S. arcticus_, _S. tundrensis_, and _S. sclateri_. _Sorex
merriami_ differs in smaller size, smaller and weaker dentition,
relatively higher coronoid, and relatively deeper and shorter dentary.
_Sorex trowbridgii_ is similar to the fossils and to _S. saussurei_.
Differences between the jaws of _S. trowbridgii_ and _S. saussurei_
seem to me to be differences of size only. _Sorex sclateri_ is larger
than the fossils and m2 is longer in relation to m1, being almost the
same size as m1. In the fossils m2 is noticeably shorter than m1, owing
to close appression of the hypoconid and protoconid and in general to a
smaller talonid area. _Sorex arcticus_ differs in larger incisor and
p4. _Sorex tundrensis_ differs in relatively narrower molars. I have
compared the fossils also with the Pliocene and Pleistocene _Sorex
taylori_ Hibbard, and find that the fossils are larger and have larger
teeth and a much wider separation of the protoconid and metaconid. I
can find no significant way in which the fossils differ from _S.
saussurei_. This of course implies similarity to _S. trowbridgii_.
Since _S. saussurei_ is a widespread species in México today and since
it occurs in the vicinity of the San Josecito area the specimens under
discussion are referred to this species.


Cryptotis mexicana (Coues)

The San Josecito collection contains 22 rami of a species of
_Cryptotis_. Many are nearly complete although none possesses the
incisor. In addition there is a rostrum that on the right side bears
the last two unicuspids, P4, M1, and M2. I have compared these fossils
with specimens of the following species of _Cryptotis_: _C. mexicana_,
_C. magna_, _C. nelsoni_, _C. thomasi_, _C. alticola_, _C. parva_, _C.
orophila_, _C. pergracilis_, _C. guerrerensis_, _C. obscura_, _C.
mera_, _C. soricina_, _C. fossor_, _C. goodwini_, _C. griseoventris_,
_C. meridensis_, _C. mayensis_, and _C. micrura_. The four species
first mentioned and the fossils seem to fall into one group. The
remaining species fall into another group characterized by a smaller
occlusal area of the talonid on all three molar teeth with respect to
the trigonid, and especially by the smaller and weaker talonid of m3
which possesses only one bladelike cusp, the hypoconid. In the first
four species the talonids are larger than in the other species when
compared to the trigonids, and the talonid of m3 possesses a well
developed hypoconid and entoconid with a distinct basin between them.
The rami of San Josecito specimens closely resemble those of _C.
mexicana_ in both size and qualitative characters. The rostrum
mentioned above differs from those of _C. mexicana_ in that the
unicuspids are larger, especially the posteriormost one. _Cryptotis
thomasi_ and _C. magna_ are eliminated from consideration here on
geographical grounds. Little difference may be seen between the rami of
_C. mexicana mexicana_ from Veracruz and _C. nelsoni_. The fossils are
referred to the former species since it has a rather wide distribution
in México in contrast to _C. nelsoni_ which is restricted to Volcán de
Tuxtla, Veracruz. The northernmost Recent occurrence of _C. mexicana_
known to me is from Las Vigas, Veracruz. As far as I know the species
has not previously been recorded from the Pleistocene.

Stirton (1930:225), in summarizing the group characters of Recent
Soricidae, listed the bicuspid talonid of m3 as one of the characters
of the "_Blarina_ group," which includes _Neomys_, _Soriculus_,
_Notiosorex_, _Chimarrogale_, _Cryptotis_, and _Blarina_. That this
character does not obtain universally within the group is demonstrated
by the unicuspid structure of the talonid of m3 of the majority of the
species of Mexican _Cryptotis_.

     I am grateful to Drs. David E. Johnson and Henry W. Setzer
     of the United States National Museum, and to Dr. John
     Aldrich and Miss Viola S. Schantz of the United States Fish
     and Wildlife Service for permitting me to examine specimens
     in their care. Also I am obliged to Professor E. Raymond
     Hall for permission to study the specimens from San Josecito
     Cave. The late Professor Chester Stock intrusted the
     specimens to Professor Hall for study and description.



LITERATURE CITED


CUSHING, J. E., JR.

    1945. Quaternary rodents and lagomorphs of San Josecito Cave,
          Nuevo León, México. Jour. Mamm., 26:2, 182-186.

HIBBARD, C. W.

    1953. The insectivores of the Rexroad fauna, upper Pliocene of
          Kansas. Jour. Paleontology, 27:1, 21-32.

MALDONADO-KOERDELL, M.

    1948. Los vertebrados fosiles del Cuaternario en Mexico. Revista
          de la Soc. Mexicana de Hist. Nat., tomo 9, nos. 1-2.

STIRTON, R. A.

    1930. A new genus of Soricidae from the Barstow Miocene of
          California. Univ. California Publ., Bull. Dept. Geol. Sci.,
          19:217-228.

STOCK, C.

    1942. The cave of San Josecito, México, new discoveries of the
          vertebrate life of the ice age. California Inst. Tech.,
          Balch Grad. School Geol. Sci. Contr., no. 361, 5 pp.

_Museum of Natural History, University of Kansas, Lawrence, Kansas.
Transmitted July 20, 1953._

25-265





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