52
southeasterly flowing stream in the early
Pleistocene to Illinoisan times (about where
the Little Blue River is now).
217
At that
time, the Loup River and the Big Blue River
appear to have been connected.
28, 149
The
location of the upper Niobrara River is not
as clear but there was a southeasterly
trending paleovalley in that area in the
Pliocene which may have connected to the
Loup system.
224, 225
Taken together, during
the Pleistocene, we have the Loup/Big Blue,
Platte, Republican and upper Niobrara
basins all trending southeasterly feeding into
the Ancestral Plains Stream which could
have been the route by which the Ringed
crayfish could migrate from the central
Ozarks to colonize these same drainages.
These drainages began to separate during the
post-Pleistocene formation of the Missouri
River. At that time a tributary began to form
(the current lower Platte River) which
migrated westward where it captured the
Loup tributaries, separating them from the
Big Blue as well as capturing the pre-
Pleistocene Platte River.
149
At the same
time, another tributary that was to become
the Niobrara River began eroding its way
westward, capturing several of the
southeast-trending drainages as well as the
upper Niobrara River.
215
CONSERVATION STATUS (NatureServe)
Global rank: G5
US Fish and Wildlife Service: N5
Committee on the Status of Endangered
Wildlife in Canada: Not present
State Designations: AR (SNR), CO (S2), KS
(S2S3), MO (S3?), NE (SNR), NY (SNA),
OK (S4), OR (SNA), WY (SNR)
Province Designations: Not found in Canada
CONSERVATION ISSUES
There are few concerns in Nebraska as it is a
widespread, native species.
