Leptotyphlops howelli sp. nov.

Howell’s worm snake

Leptotyphlops macrops — Broadley & Wallach, 1996: 162 (part); McDiarmid et al., 1999: 35 (part); Spawls et al., 2002: 303 (part).

Holotype. NMZB 10455, a male from Mchungu Forest Reserve, Rufiji District, Piwani Region, Tanzania (07°44'S, 39°17'E, elevation 15 m), collected by K.M. Howell (field no. 7041), 5 September 1990. In camp in woodland on surface after rain.

Paratype. NMK /O. 2077, a male from Yala River, Nyanza Province, Kenya.

Diagnosis. A member of the Leptotyphlops macrops complex, distinguished by its low total middorsal scale count (229–237) from L. pembae (247–269) and L. macrops (272–322). It also differs from both these taxa in numerous visceral characters.

Etymology. Named for the collector K.M. Howell, in recognition of his major contributions to Tanzanian herpetology.

Description. The head shield arrangement does not differ from that of Leptotyphlops macrops. Head slightly wider than neck, with a moderate bulge over the eye in dorsal view.

Snout rounded in lateral view, with a shallow concavity to preoral portion of rostral; rostral broad (0.48– 0.50 head width, mean = 0.49), subrectangular, truncated at the level of the centre of the eye posteriorly; supranasal subequal in width to the ocular. Behind rostral, lip bordered by infranasal (nostril nearer to rostral than supralabial along nasal suture), moderate anterior supralabial twice as high as long and equal in width along lip to that of infranasal, broad ocular, and tall posterior supralabial that reaches the level of the centre of the eye dorsally; eye large and distinct, bulging beyond dorsal head profile, with a clearly defined iris; supraoculars smaller than frontal and postfrontal; interparietal slightly wider than frontal and postfrontal; parietals oblique, in contact with supralabials; occipitals fused and enlarged. Temporal single. Prominent tubercles on rostral, nasals and oculars. No mental, five infralabials, third largest. Paratype variations in parentheses below.

Total dorsals 237 (229); 14 scale rows round body; 10 scale rows round middle of tail; subcaudals 32 (30).

Total length 158 mm (140 mm); tail 18 mm (15 mm), slightly tapering, then ending abruptly in a sharp point; midbody diameter 2.6 mm (2.1 mm).

Total length/diameter 61 (67); total length/tail length 8.8 (9.3).

Dorsum and venter uniformly black, except for a small white patch on the chin.

Habitat. Coastal forest /savanna mosaic (holotype) or gallery forest (paratype).

Distribution. When the holotype was recorded from the Rufiji Delta, 15 m, it was suggested that it might represent a southern subspecies of Leptotyphlops macrops (Broadley & Wallach, 1996). However, the discovery of a second specimen from the Lake Victoria Basin, 1000 km to the northwest, suggests that these are relict populations of the basal species of this complex at the periphery of the range of the derived L. macrops (Plate 5). The insular L. pembae seems to occupy an intermediate position.