Physical characteristics

Perhaps the most conspicuous physical characteristic of blindsnakes is their small size. Although Typhlopidae includes a small number of "giant" species that may reach over 2 ft (61 cm) in total length (e.g., Ramphotyphlops proximus, R. un-guirostris, Rhinotyphlops acutus, R. schlegelii, Typhlops angolensis, T. lineolatus, and T. punctatus), most species are much smaller, and many reach a maximum adult length of less than 1 ft (31 cm). The smallest blindsnakes known are hatchling Ramphotyphlops braminus, which measure little more than 2 in (5 cm) in length, less than 0.04 in (1 mm) in width, and weigh only 0.005 oz (0.13 g). In contrast, the largest blindsnake, Rhinotyphlops schlegelii, reaches a maximum length of 3.1 ft (95 cm),

A blindsnake above ground after a heavy rain in the Solomon Islands. (Photo by Animals Animals ©W. Cheng. Reproduced by permission.)

a width of almost 1.2 in (3 cm), and a weight of nearly 1.1 lb (0.5 kg).

In general, typhlopids are somewhat stouter than other blindsnakes (Anomalepididae and Leptotyphlopidae). However, "aspect ratios" (total length divided by body width) vary widely within this family, ranging from 16 (in the stocky Brazilian species Typhlopspaucisquamus) to at least 130 (in the extremely slender Australian species Ramphotyphlops grypus). In most forms the body is relatively round in cross-section and is nearly uniform in width from the head to the base of the tail. In some larger species, however, the rear part of the body may become markedly distended in adults due to the deposition of fat throughout the posterior portions of the abdominal cavity.

The body scales of typhlopids are smooth, shiny, and strongly overlapping. As in Anomalepididae and Leptoty-phlopidae, these scales are more or less circular in shape (at least along their posterior margins) and uniform in size. The only enlarged scales are the anal shields (numbering between one and five) and the scales surrounding the head. The number of longitudinal scale rows encircling the body ranges from 16 to 44, and the number of transverse scale rows along the length of the body ranges from 169 to 709. The body scales are remarkably thick, providing these snakes with an effective line of defense against the bites and stings of the insects on which they feed. This thickening of the epidermis also has a profound effect on ecdysis (shedding of skin). The shed skins of typhlopids (especially those of larger species of Ramphotyphlops, Rhinotyphlops, and Typhlops) are much thicker than those of other snakes and often have a rubbery consistency. In addition, the skin is usually shed in a series of rings rather than in a single piece as in most other snakes.

Like other blindsnakes, typhlopids have small, ventrally placed mouths and highly reduced eyes that are covered by the enlarged scales surrounding the head. However, the general shape of the head is much more variable in Typhlopi-

dae than in Anomalepididae and Leptotyphlopidae. The snout may be bluntly rounded (Cyclotyphlops, most Typhlops, and many Ramphotyphlops), flattened and anteroventrally sloping (Xenotyphlops and some Rhinotyphlops), acutely conical (Acutotyphlops), hooked (e.g., Ramphotyphlops grypus), or trilobulate (Ramphotyphlops bituberculatus) in shape. In most species epidermal glands are visible along the edges of the anterior head scales. In addition, the head shields house numerous tactile organs, and in some taxa (e.g., Xenotyphlops and some Rhinotyphlops) flexible, papilla-like structures project externally from the anterior-most scales surrounding the snout.

The tail is relatively short in most typhlopids, and in many species of Rhinotyphlops and Typhlops, this structure accounts for less than 1% of the snake's total length. However, in some species of Acutotyphlops and Ramphotyphlops the tail is often somewhat longer (5% or more of total length), and in one species that appears to have strong arboreal tendencies (Ramphotyphlops cumingii), the tail may account for as much as 10% of the snake's total length. The tail terminates in a sharp, narrow apical spine in most species, but this feature is absent in some taxa (e.g., Xenotyphlops and the two Asian species of Rhinotyphlops), and in others it may become somewhat enlarged (e.g., Typhlops depressiceps and Acutotyphlops subocularis).

Coloration and patterning are highly variable within Ty-phlopidae. The majority of species are essentially unpat-terned, and most are relatively dark in color (some shade of black, gray, or brown). A wider array of colors and patterns are seen in the genera Rhinotyphlops and Typhlops. Although both of these genera include rather drab, unicolored forms, they also include species boldly patterned with speckles (e.g., R. schlegelii), blotches (e.g., T. congestus), or stripes (e.g., R. unitaeniatus). In such taxa, bright colors (blue, orange, yellow, white) are often incorporated into these elaborate patterns. In most blindsnakes the ventral scales are somewhat lighter in color than the dorsal scales, and in some species (e.g., T. retic-ulatus) this difference is especially striking. Finally, a small number of typhlopids appear to lack pigmentation entirely (e.g., Xenotyphlops grandidieri).

The most distinctive internal anatomical features of ty-phlopids relate to their jaw apparatus. In contrast to other snakes, the lower jaw in Typhlopidae is rigid and toothless. The only teeth in the skull are located on the maxillae, which are suspended from the rest of the skull almost entirely by muscles and ligaments. Also peculiar is the orientation of the maxillae, which are positioned horizontally in the mouth. As a result, the transversely oriented maxillary tooth rows point directly posteriorly toward the throat. As in Leptotyphlopi-dae, the hyoid (tongue skeleton) is Y-shaped and positioned far behind the head. The pelvic apparatus is highly reduced. In most species only the rod-like ischia become ossified, and the pubes and ilia (when present) are generally fused and remain cartilaginous. Femora are absent. In addition to these skeletal characteristics, several unique soft anatomical features have also been documented in Typhlopidae. Perhaps the most noteworthy among these is the solid distal portion of the hemipenis in males of the genus Ramphotyphlops, a feature that is unique among squamates.

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