. Monographs of North American rodentia [microform]. Rodentia; Paleontology; Rongeurs; Paléontologie. â i:. I igfilS;!: -. -ilMl'; â ;â ., 822 MONOORArnS OF NOUTH AMERICAN EODENTIA. approaches Cynomys. While S. empetra deviates toward Otospermophilus, S. richardsoni strongly approaches Cynomys, as do 8. spilosoma and 8. obsoletus to Jctidomys, especially in the general contour of the skull. In IcHdomys, there is an approach, through S. mexicanus, toward Tamias, while S. Jrank- lini, in its full, broad, and rather long tail and prominent ears, and sonaewhat in the general shape of the skull an
. Monographs of North American rodentia [microform]. Rodentia; Paleontology; Rongeurs; Paléontologie. â i:. I igfilS;!: -. -ilMl'; â ;â ., 822 MONOORArnS OF NOUTH AMERICAN EODENTIA. approaches Cynomys. While S. empetra deviates toward Otospermophilus, S. richardsoni strongly approaches Cynomys, as do 8. spilosoma and 8. obsoletus to Jctidomys, especially in the general contour of the skull. In IcHdomys, there is an approach, through S. mexicanus, toward Tamias, while S. Jrank- lini, in its full, broad, and rather long tail and prominent ears, and sonaewhat in the general shape of the skull and rather small first upper premolar, rather inclines toward Otospermophiuu. As is evident from the foregoing remarks, the complex inosculations of Sciurus, Tamias, Cynomys, and the several divisions of Spermophilus, render it impossible to arrange them serially in a single line. The following dia- grammatic disposition to some extent expresses their mutual aflSnities, as well as their relationship to Arctomys. SCIURDS. \ OTOaPBRMOFHILUS. Tamias. Cynohtb. ICnDOMYS. Akctohts. The absence of any broad gaps among the many species composing the above-named groups leads to the inference of their comparatively recent diverg- ence from some common ancestral type, which may or may not have been something nearer Arctomys than Sciurus, or something quite diflferent from either. The extinct species of the Tertiary formations,* of which there are indications of a large number, none of which, unfortunately, are as yet well known, were mainly of large size, most of them exceeding the existing species of Cynomys, while some equalled and even exceeded the largest species ' For BU ocGoant of theM, boo the ooDolnding portion! of tbli Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Coues, Elliott, 1842-1899; Allen
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Keywords: ., bookcentury1800, bookdecade1870, bookpub, booksubjectpaleontology
