University of Kansas Publications Museum of Natural History Volume 5, No. 32, pp. 543-561, 12 figures in text December 1, 1953 University of Kansas LAWRENCE 1953 University of Kansas Publications, Museum of Natural History Editors: E. Raymond Hall, Chairman, A. Byron Leonard, and Robert W. Wilson Volume 5, No. 32, pp. 543-561, 12 figures in text December 1, 1953 University of Kansas Lawrence, Kansas printed by ferd voiland, jr., state printer topeka, kansas 1953 By JOHN A. WHITE Contents...

The supraspecific categories of the chipmunks, as in most other groups of squirrels, have been a source of controversy for many years. Before presenting new evidence and a review of older evidence bearing on the problem, it seems desirable to review briefly in chronological order, the taxonomic history of the genera and subgenera of the chipmunks....

Linnaeus (1758:64) described the eastern North American chipmunks under the name Sciurus striatus and based his description on that of Catesby (1743:75). The Asiatic chipmunk was first described, under the name Sciurus sibiricus , by Laxmann (1769:69). Schreber (1785, 4:790) separated the Asiatic and North American chipmunks into the Asiatic and American varieties. Gmelin (1788:50) followed Schreber and, employing trinomials, used the names Sciurus striatus asiaticus and S. s. americanus . Illig

Characters previously mentioned in the literature as having taxonomic worth for supraspecific categories of chipmunks were checked by me on specimens old enough to have worn permanent premolars. Some structural features not previously used were found to have taxonomic significance. The baculum in each of the supraspecific categories of sciurids of North America was examined; the bacula were processed by the method described by White (1951:125) to obviate “variation” caused by shriveling of the s

The following paragraphs treat the characters listed by Howell, Ellerman, and Bryant, and such additional characters as I have found useful in characterizing the genera and subgenera of chipmunks. Some of the findings, I think, illustrate how study of such mammalian structures as the baculum, malleus, and hyoid apparatus—structures that seem to be little influenced by the changing external environment—clarifies relationships, if these previously were estimated only from other parts of the anatom

Structure of the Malleus. —The malleus in chipmunks is composed of a head and neck, a manubrium which has a spatulate process at the end opposite the head, and a muscular process situated about halfway between the spatulate process and the head of the malleus. An articular facet begins on the manubrium near the neck and spirals halfway around the head of the malleus. A lamina extends from the anterior edge of the head and neck, tapers to a point and joins the tympanic bulla anteriorly where ther

Shape of the infraorbital foramen. —In the subgenus Eutamias and in the genus Tamias the infraorbital foramen is rounded, whereas in most species of the subgenus Neotamias the foramen is slitlike. In Eutamias townsendii , however, the infraorbital foramen is rounded as much as in the subgenus Eutamias and in the genus Tamias . Width of the postorbital process at base. —The postorbital process is broader at the base in the subgenus Eutamias and in the genus Tamias than in most species of the subg

The following alleged characters have been mentioned in the literature. Since the degree of expression of these features is so slight, or since there is marked variation within one or more natural groups of chipmunks, no reliance is here placed on these features. They are as follows: (1) Degree of the posterior projection of the palate; (2) relative size of the auditory bullae; (3) position, in relation to P4, of the notch in the posterior edge of the zygomatic plate; (4) size of m3 in relation

As shown in table 1 , there are ten characters by means of which Eutamias and Tamias can be separated consistently. The subgenus Eutamias occurs on the Asiatic side and the subgenus Neotamias occurs on the North American side of Bering Strait, yet the two subgenera agree in the ten features referred to. Although the subgenus Neotamias and the genus Tamias occur together in parts of the United States and Canada, they differ in the ten features, indicating that the subgenera Eutamias and Neotamias

It must be pointed out here that the subgenus Neotamias always differs from both the subgenus Eutamias and the genus Tamias in pointed versus rounded pinna of ear (see table 2 ) and in the supraorbital notch being slightly posterior to or even with, instead of distinctly anterior to, the posterior notch of the zygomatic plate. The relative position of these two notches, however, seems to be a matter of relative (heterogonic) growth. Further, the base of the postorbital process of the frontal usu

These differences of Neotamias are so slight in comparison with the similarities (ten features mentioned above) that Neotamias here is accorded only subgeneric rank under the genus Eutamias , instead of generic rank. Howell’s (1929) arrangement of the genera and subgenera of chipmunks is judged to be correct as indicated by the following arrangement that I propose....

Genus Eutamias Trouessart Eutamias Trouessart, E. L. Catal. Mamm. viv. et foss., Rodentia, in Bull. Soc. d’Etudes Sci. d’Angers, 10:86-87, 1880. Type Sciurus striatus asiaticus Gmelin. Eutamias , Merriam, C. H., Proc. Biol. Soc. Washington, 11:189-190, July 1, 1897. Eutamias , Howell, A. H., N. Amer. Fauna, 52:26, November 30, 1929. Tamias , Ellerman, J. R., The families and genera of living rodents. British Mus. (Nat. Hist.), 1:426, June 8, 1940. Tamias , Bryant, M. D., Amer. Midland Nat., 33:7

Chipmunks are small striped squirrels that inhabit the Holarctic Realm and that are found in similar niches in each of the three regions: Palearctic, western Nearctic, and eastern Nearctic. Ellerman (1940) and Bryant (1945) placed the chipmunks in three subgenera, corresponding to the regions mentioned above, under the one genus Tamias . Critical examination of new and old evidence reveals, nevertheless, that the subgenera Eutamias and Neotamias of the genus Eutamias are more closely related to

1. Eutamias and Tamias are distinct genera of chipmunks. 2. The subgenera Eutamias and Neotamias are valid, for, Eutamias sibiricus differs from all the species of the subgenus Neotamias to a greater degree than these species differ from one another. 3. The genera Eutamias and Tamias probably evolved from two distinct lines of sciurids; one line ( Eutamias ) is represented by the tribe Callosciurini, and the other ( Tamias ) by the tribe Marmotini....

Catesby, M. 1743. The natural history of Carolina, Florida, and the Bahama Islands, etc., 2:i-xliv, 1-20, 1-100. Ellerman, J. R. 1940. The families and genera of living rodents. British Mus. (Nat. Hist.), Vol. 1, pp. xxvi + 689, 189 figs., June 8. Ellerman, J. R. , and T. C. S. Morrison-Scott. 1951. Checklist of Palearctic and Indian mammals. British Mus. (Nat. Hist.), pp. 1-810, 1 map, November 30. Gmelin, J. F. 1788. Systema Naturae. 1:1-500. Howell, A. H. 1929. Revision of the American chipmu