. Fig. 128. Superimposition of Coloradan limits of 28 species of Chihuahuan Faunal Element. cies, Plecotus townsendii, occurs well east- ward into the Ohio Valley. Three species (Sylvilagus audubonii, Dipodomys ordii, Reithrodontomys megalotis) have established contact between Great Plains and Great Basin segments through the Wyoming Basin and thus surround the Southern Rocky Mountains. Onychomys leucogaster is a possible fourth such species. However, the northern grass- hopper mouse is herein considered to repre- sent Great Basin and Campestrian faunal elements, inasmuch as the species ranges
. Fig. 128. Superimposition of Coloradan limits of 28 species of Chihuahuan Faunal Element. cies, Plecotus townsendii, occurs well east- ward into the Ohio Valley. Three species (Sylvilagus audubonii, Dipodomys ordii, Reithrodontomys megalotis) have established contact between Great Plains and Great Basin segments through the Wyoming Basin and thus surround the Southern Rocky Mountains. Onychomys leucogaster is a possible fourth such species. However, the northern grass- hopper mouse is herein considered to repre- sent Great Basin and Campestrian faunal elements, inasmuch as the species ranges little south of the Mexican boundary. Urocyon cinereoargenteus (not mapped) is included with the Chihuahuan element on the basis of its range in and near Colorado. Based on its continental distribution, the spe- cies probably would be considered a eury- chore. Although limits of Chihuahuan species occur generally over western United States, the area of greatest coincidence of limits obviously is in Colorado and immediately adjacent areas (Fig. 127G). It is of some interest to examine those Coloradan limits in more detail. A superimposition of Colo- radan limits of the 28 species of the Chihua- huan Faunal Element is shown in figure 128; the pattern is like that shown in figure 127G, but resolution is substantially greater. At most, a single member of the Chihua- huan element (Plecotus townsendii) crosses the Continental Divide in Colorado. A pre- ponderance of limits occurs in major valleys of the Western Slope. Some kinds range into the San Luis Valley. On the Eastern Slope, four recurrent pat- terns are indicated. Some species (Sylvilagus
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Keywords: ., bookcentury1900, bookcollectionbiodiversity, booksubjectmammals
