Evolution and Classification of the Pocket Gophers of the Subfamily GeomyinaeRussell, Robert J.
Science
Evolution and Classification of the Pocket Gophers of the Subfamily Geomyinae
Russell, Robert J.
Pocket gophers
The teeth
are small, and suggest that a smaller species of _Geomys_ may have
occurred along with the more common and larger _G. quinni_ during the
early Pleistocene (see discussion beyond of the Saunders _Geomys_).
_Geomys quinni_ was widespread and common throughout the central Great
Plains from the late Pliocene (Rexroad fauna) through the early
Pleistocene (Nebraskan and Aftonian deposits).
Hibbard (1956:179) referred the pocket gopher remains taken from the
Saunders local fauna in Meade County, Kansas, to _Geomys tobinensis_,
a small species having continuous enamel bands around the lower
premolar in younger specimens. The Saunders local fauna was deposited
in the late Aftonian and is younger than the Deer Park local fauna
discussed above. Paulson (1961:138) later pointed out that the
Saunders _Geomys_ is distinct from _Geomys tobinensis_; hence, the
small pocket gopher from the Saunders local fauna is probably an
unnamed species, perhaps more closely allied to _paenebursarius_
than to _quinni_. The small _Geomys_ reported from the Aftonian
Broadwater-Lisco local fauna of Nebraska (Schultz and Stout, 1948:563)
may also be the same as the Saunders pocket gopher, but the smaller
adult specimens occurring in the same bed with larger specimens
probably are females and the larger specimens males. In all living
Geomyini females have smaller skulls than males.
The Irvingtonian provincial age is currently regarded as Middle
Pleistocene and includes the late Kansan glaciation (that part
occurring after the glacial maximum) and the Yarmouthian interglacial
(see Hibbard _et al._, 1965:512-514). The Irvingtonian provincial
age, therefore, follows the late Blancan provincial age of the early
Pleistocene and is succeeded by the Rancholabrean provincial age of
the late Pleistocene. No specimen of an Irvingtonian _Geomys_ is
referable to any living species. Two Irvingtonian species have been
described. Hibbard (1944:735) named _Parageomys tobinensis_ [= _Geomys
tobinensis_] from the Tobin local fauna of Russell County, Kansas.
This species since has been reported from the Cudahy local fauna of
Meade County, Kansas (Paulson, 1961:137). Hibbard (1956:183) also
identified as _Geomys tobinensis_ the pocket gopher recovered from the
Saunders local fauna, a late Aftonian deposit of Meade County, Kansas,
and reduced the technical name _Parageomys_ from generic to subgeneric
rank. Paulson (_op. cit._:138) pointed out that the Saunders specimens
differ from _G. tobinensis_, and he, therefore, restricted the name
to the small _Geomys_ of the Cudahy and Tobin local faunas of
Irvingtonian provincial age. _G. tobinensis_ is markedly smaller than
the Blancan _G. quinni_. The Cudahy and Tobin local faunas are of
approximately the same age, and presently both are included in one
unit, the Cudahy fauna. The Cudahy fauna is considered to have been
deposited in late Kansan as it occurs in strata immediately below the
Pearlette ash.
Public-domain text, read in full here on John Shaqi.
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