2. A. Antiplantar view of right hind foot, × 9.
B. Terminal part of second toe of left hind foot, and its claw, in lateral view, × 9.
The five-lined pattern is characteristic of the hatchling, but gradual ontogenetic change results in its dulling, suppression, and eventual loss. In the hatchling the ground color of the head and body is black or dark brown, with five milky white longitudinal stripes extending the length of the head and body, and on the basal one-fourth of the tail. The five light lines are of approximately equal width, and are separated by dark interspaces 11⁄2 to 2 times as wide. The mid-dorsal stripe includes most of the two mid-dorsal scale rows. Posteriorly it extends onto the base of the tail, where it becomes increasingly suffused with the blue color of the tail, widens, and loses its identity. In the nuchal region, this dorsal stripe narrows and splits into left and right branches, which diverge anteriorly to form a lyrate pattern on the head. On either side of the dorsal stripe are the dark interspaces, nearly twice as wide as the stripe itself and tapering to a point posteriorly on the tail, likewise tapering anteriorly to a point immediately above and in front of the eye. Lateral to these dark areas are the dorsolateral stripes; they extend from the basal one-fourth of the tail anteriorly onto the head along the superciliary region, tapering to a point on the anterior superciliary. Below these stripes are the dark lateral areas which extend from the basal part of the tail anteriorly along the sides of body and neck region (including the upper half of the aperture of the ear), eye region, and loreal region. Below this dark area on each side is the lateral stripe. It extends along the sides just above the level of the limb insertions (broken or pinched to a fraction of its average width above the hind limb insertion), broken by the ear opening, and extending anteriorly to include all the supralabial scales (with the exception of their upper edges) and the rostral. Here the left and right lateral stripes may be said to join; however in the facial region these stripes are not well defined, partly because the dark areas that border their lower edges do not extend so far forward. This lowermost dark area is about equal in width to the lateral stripe. It extends from the posterior infralabials posteriorly, to include the fore- and hind-limbs, and onto the basal part of the tail. The ventral surface of the head and body is dull white or pearly gray.
Thus, there are 12 longitudinal bands of color on the body: the five narrow, subequal, pale lines separated by the six dark areas, of which the dorsal and dorsolateral are broad and of approximately equal width, while the ventrolateral is narrower; and lastly the broad, pale ventral area.
Fig. 3. A. Osteoderm of an old adult male, from near the midline of the back, × 25.
B. Another osteoderm from same male, from belly near midline, × 25.
C. Another osteoderm from side of same male, at a point approximately halfway between foreleg and hind leg, × 25.
D. Osteoderm of a juvenile obtained in April, from near midline of back, × 25.
E. Tongue from dorsal view, shown in its normal position in the lower jaw, × 21⁄2.
The tail in young individuals is bright blue. In Eumeces the tail characteristically has a color different from that of the body, and is usually more conspicuous; in many species it is blue, but in others it may be purple, greenish-blue, red, pink, or orange. Hatchlings have the most brightly colored tails, and as growth proceeds the colors gradually become duller. In E. fasciatus the bright colors of the tail are mostly or entirely lost in old adults, especially in males, and in individuals of either sex that have lost their original tails and regenerated new tails. Young which lose their tails and regenerate them at an early age have the regenerated portions colored almost as brightly as the originals at first.
The skin is tight fitting and relatively thick, stiffened by a bony armor. A small bony plate or osteoderm underlies each scale. Oliver (1951:127) has called attention to the pattern of ornamentation on the osteoderms, which becomes more complex with advancing age. He has suggested the possibility that age might be accurately determined on the basis of extent of osteodermal ornamentation. I have compared osteodermal ornamentation in marked individuals of known age, but have found it to be of limited applicability as a method of age determination; size and pattern are probably more satisfactory bases for estimating age, even though they do not permit definite aging of old adults and are not infallible for skinks short of adult size. In adult E. fasciatus the pattern of ornamentation is closely similar to that figured for E. laticeps by Oliver (op. cit.) and also resembles the pattern shown for an Old World skink, Mabuya multifasciata, as figured by Smith (1935: 2). The pattern differs somewhat in osteoderms on different parts of the body, and is most nearly symmetrical in those near the midline on either dorsal or ventral surface (Figure 3).
Relationships
Eumeces is a widespread genus occurring in the New World in southern Canada and southward into Costa Rica. The greatest number of forms is in Mexico. In the Old World numerous species occur in southeastern Asia and on adjacent islands, and other species occur westward across southern Asia, and across North Africa to Morocco, with a major break in the continuity of distribution in the Himalayan region. Taylor in his revision recognized 57 forms with fifty full species, belonging to 15 major groups within the genus. Since then only relatively minor changes in classification have been proposed. Several new species and subspecies have been named, and several species have been relegated to the status of subspecies.
Within the genus there are several groups that have representatives in both the New World and the Old World. Smith and Etheridge (1953:159) point out that the most primitive line of Eumeces is best represented in the Old World, where there are two groups and nine species, while in the New World this line has only three tropical relict forms. For this reason, Smith and Etheridge concur with Taylor (1936:67) in considering the genus to be of Old World origin; but the two main lines of the genus (the four-lined and five-lined stocks) are both regarded as being of New World origin. According to this idea, the Asiatic members of these two groups migrated from the New World. In the early Tertiary, warm temperate climates extended north to the Arctic Circle, and Eumeces, or at least some of its species, may have had a distribution straddling migration routes to both North America and Asia.
Of the 15 groups within the genus, the fasciatus group, with a dozen species, has more representatives than any other. The fasciatus group is characterized by having the tail bright blue with dorsal body pattern of five light lines on a darker ground color; mid-dorsal line bifurcating on head to form lyrate markings (this striped pattern and bright color of the tail becoming dull or obsolete in the adults); medial preanal scales overlapped by those lateral to them; two pairs of nuchals; no postfemoral pocket; four supraoculars; scales on sides of body in parallel rows. The characters that separate members of the fasciatus group from each other are minor. The width and position of the light lines differ somewhat among them. The mid-dorsal light line bifurcates either on the nuchals or on the parietals. The complex of scales in the temporal region differ in shape and relative size.
The following table, compiled mostly from information set forth by Taylor (1936:186–283), indicates some of the main differences and similarities between species in the chief characters upon which the classification is based.
The close resemblance between E. fasciatus and its Asiatic relatives is remarkable considering the great distance separating them and the long time that must have elapsed since their isolation began. Some of the Asiatic forms differ from each other almost as much as they differ from fasciatus. Of the Asiatic species, elegans, tamdaoensis, oshimensis, and marginatus differ from fasciatus in markedly larger size; elegans, marginatus, oshimensis, and stimsonii differ in lacking a postnasal; all but tamdaoensis tunganus and xanthi differ in having only a single