Atractaspis branchi, Roedel, Mark-Oliver, Kucharzewski, Christoph, Mahlow, Kristin, Chirio, Laurent, S. G. Pauwels, Olivier, Carlino, Piero, Sambolah, Gordon & Glos, Julian, 2019

Roedel, Mark-Oliver, Kucharzewski, Christoph, Mahlow, Kristin, Chirio, Laurent, S. G. Pauwels, Olivier, Carlino, Piero, Sambolah, Gordon & Glos, Julian, 2019, A new stiletto snake (Lamprophiidae, Atractaspidinae, Atractaspis) from Liberia and Guinea, West Africa, Zoosystematics and Evolution 95 (1), pp. 107-123 : 107-112

Atractaspis branchi sp. n. Figures 1, 2, 3, 4; Tables 1, 2, 3

Holotype.

ZMB 88529 (field and tissue number RG97; 16S GenBank MK501382), female, Liberia, Lofa region, Foya Forest, 08°01'16.2"N, 010°25'31.4"W, 317 m a.s.l., near a small rocky creek in primary lowland rainforest, 6 April 2018, coll. M.-O. Rödel, G. Sambolah & J. Glos.

Paratype.

MSNS Rept 280 (field number 9294X, skull broken; 16S GenBank MK501383), female, Guinea, Nzérékoré Region, Koyakoélé, 07°44'54"N, 009°11'28"W, 393 m a.s.l., 26 December 2011, coll. L. Chirio.

Additional material.

IRSNB not yet accessioned (field number 9314X), Guinea, Nzérékoré Region, Belefanin, 07°55'28"N, 009°01'33"W, 486 m a.s.l., coll. L. Chirio (voucher, only head and anterior part of body; snake still in Africa and thus not available to us).

Diagnosis.

External morphology, skull anatomy and molecular data (see below) clearly supports the position within the genus Atractaspis . The new species can be only mistaken morphologically with species from Laurent’s (1950) section ‘D’, his reticulata -group. In particular it differs from all other species of the genus, except A. reticulata and A. corpulenta (including the West African A. c. leucura), by the fusion of the 2nd infralabial with the inframaxillary. From A. corpulenta it differs by a much higher ventral count (276-288 vs 178-208), lower number of dorsal scale rows at midbody (19 vs 23-29), divided anal plate and subcaudals, and the absence of a white colored tail tip (present in A. c. leucura); from A. reticulata it can be distinguished by a lower ventral count (276-288 vs 304-370), and 19 (the paratype has mostly 19 scale rows, but 20 at midbody) dorsal scales rows at midbody (19 scale rows present in the A. reticulata holotype, other vouchers having 21-23 rows) (Table 1). The new species further differs from A. corpulenta by a more slender body and from A. reticulata by a longer tail compared to body length.

Holotype description.

Subadult female; slender snake with moderately robust body and short and rounded head; no constriction between head and body; snout-vent length 267 mm; tail length 17 mm (ratio snout-vent length / tail length = 15.7); head length 7.7 mm (tip of snout to angle of jaws) / 7.1 mm (tip of snout to end of parietal suture); head width 5.7 mm (at widest point) / 3.6 mm (distance between the outer margins of supraocular at the level of mid eye); nostrils directed laterally; dorsally measured distance between nostrils 2.9 mm; small eyes directed dorsolaterally; eye diameter 1.0 mm (horizontal) / 0.8 mm (vertical), pupil roundish; distance from lower border of eye to mouth 2.0 mm; distance between anterior edge of eye to posterior edge of nostril 1.9 mm; 5 supralabials, the 4th being the largest, the 3rd and 4th in contact with eye; 5 infralabials, the 1st and 3rd touching the inframaxillary, the 2nd fused with the inframaxillary, the 3rd being the largest; the 1st pair of infralabials in contact behind mental; rostral visible from above, rounded in lateral and dorsal views; nasal divided, touching 1st to 3rd supralabial and preocular, nostril nearly completely situated in the anterior part of nasal; loreal absent; 1 small preocular, not in contact with frontal, touching 3rd supralabial; 1 postocular distinctly larger than preocular, touching temporal and 4th supralabial; 1 small supraocular (length 1.6 mm); 1 very large anterior temporal (length 2.7 mm) followed by 2 posterior temporals; beside the temporals only 3 further scales touching the posterior borders of parietals; 1 pair of distinctive inframaxillaries touched by 3 gular scales; mental groove present; top of head covered by 9 scales; suture of internasals 0.7 mm long; suture of prefrontals 0.8 mm long; frontal slightly longer than wide (3.1 mm vs 2.8 mm); suture of parietals 1.8 mm long; dorsal scales smooth, rhombic shaped, decreasing gradually in size dorsally, apical pits absent, but all dorsal scales with a single little pore near the center of the scale; 3 preventrals, 276 rounded ventral scales; anal plate divided; subcaudals divided, 25/25+1; ratio ventrals / subcaudals: 11.0; dorsal scale rows straight.

Dorsal scale row reduction:

Supracaudal scale row reduction:

Color in life: dorsal scales of uniform, shiny, purple-brown with light grey margins, venter marginally lighter, broad tongue fleshy (Fig. 1). Color in preservation: dorsally uniform dark grey with a purplish hue; all scales with lighter margins, venter lighter; mental, first pair of infralabials and lower margin of the rostral pale.

Paratype description.

Adult female, skull broken; slender snake with moderately robust body and short and rounded head; no constriction between head and body; snout-vent length 689 mm; tail length 32 mm (ratio snout-vent length / tail length = 21.5); head length 7.7 mm (tip of snout to angle of jaws) / 11.7 mm (tip of snout to end of parietal suture); head width 10.3 mm (at widest point) / 6.2 mm (distance between the outer margins of supraocular at the level of mid eye); nostrils directed laterally; dorsally measured distance between nostrils 4.7 mm; small eyes directed dorsolaterally; eye diameter 1.5 mm (horizontal) / 1.0 mm (vertical), pupil roundish; distance from lower border of eye to mouth 3.6 mm; dis tance between anterior edge of eye to posterior edge of nostril 3.6 mm; 5 supralabials, the 4th being the largest, the 3rd and 4th in contact with eye; 5 infralabials, the 1st and 3rd touching the inframaxillary, the 2nd fused with the inframaxillary, the 3rd being the largest; the 1st pair of infralabials in contact behind mental; rostral visible from above, rounded in lateral and dorsal views; nasal divided, touching 1st to 3rd supralabial and preocular on the right side (left side preocular is fused with the prefrontal), nostril nearly completely situated in the anterior part of nasal; loreal absent; 1 small preocular on the right side (left side missing), not in contact with frontal, touching 3rd supralabial; 1 postocular little larger than preocular, touching temporal and 4th supralabial; 1 small supraocular (length 2.6 mm); 1 very large anterior temporal (length 5.2 mm) followed by 2 posterior temporals; beside the temporals only 3 further scales touching the posterior borders of parietals; 1 pair of distinctive inframaxillaries touched by 3 gular scales; mental groove present; top of head covered by 9 scales; suture of internasals 1.4 mm long; suture of prefrontals 1.6 mm long; frontal slightly longer than wide (4.9 mm vs 4.8 mm); suture of parietals 2.8 mm long; dorsal scales smooth, rhombic shaped, decreasing gradually in size dorsally, apical pits absent, but all dorsal scales with a single little pore near the center of the scale; 5 preventrals, 288 rounded ventral scales; anal plate divided; subcaudals divided, 19/19+1; ratio ventrals/subcaudals: 15.6; dorsal scale rows oblique.

Dorsal scale row reduction:

Supracaudal scale row reduction:

Color: Dorsal and ventral scales of freshly dead individual a dark grey with lighter grey to almost white margins; dorsal scales with slight rainbow shimmer (Fig. 2).

Additional material.

The only available data, collected in the field, of this specimen (Fig. 2; only head and anterior body left), were sublinguals fused on each side with the 2nd infralabials; 4/4 infralabials (including the ones fused with the sublinguals); 2 preventrals +> 56 ventrals).

Skull anatomy.

The skull anatomy of most Atractaspis species is unknown, as is the phylogenetic relationships of our new species. We here compare ct-scans and measurements of the holotype and paratype of Atractaspis branchi sp. n. to the morphologically most similar Atractaspis species, A. reticulata (NRM 1796, holotype of A. r. reticulata; and ZMB 28500), and two other Atractaspis species, A. boulengeri matschiensis (ZMB 11040) and A. aterrima (ZMB 8016). In general, skull shape was very similar (Figs 3-5; Table 3). However, the short and stout skull of the new species can be distinguished from the representatives of the three other species by shorter frontals compared to skull length with only a shallow inclusion of the nasals (ratio length of frontals to skull length: 0.25‒0.26 vs 0.28‒0.31) and a higher number of palatine teeth (3 vs 0 or 2). Furthermore A. branchi sp. n. differs from A. boulengeri matschiensis and A. aterrima by the extension of the nasals anteriorly, being longer than level of premaxilla (vs nasals shorter than level of premaxilla), and from A. boulengeri matschiensis by a transverse anterior border of the premaxilla in dorsal view (vs a convex anterior border). However, we examined only one or two ( A. branchi and A. reticulata ) individuals of each taxon, and intraspecific variability so far has not been investigated in any Atractaspis species, but it might be expected. For instance, the measurements and scans of the two types of A. branchi sp. n. indicate that smaller specimens may have shorter fangs and larger eyes (Table 2).

Broadley (1990: fig. 121) figured an A. bibronii Smith, 1849 that possesses one fang (no replacement teeth) on each maxilla, but small teeth on palatine (4) and dental (3) bones. Cundall and Irish (2008: fig. 2.87D) figured functional and replacement fangs and two palatine teeth.

Molecular data.

The 16S sequences of the two type specimens of Atractaspis branchi sp. n. were almost identical (1% difference, 509 bp used for comparisons). Uncorrected pairwise comparisons to the respective part of 16S sequences of other Atractaspis revealed the following differences (first number refers to comparison with A. branchi holotype, the second to the paratype): Atractaspis boulengeri (4-3%, 499 bp, 485 bp), A. corpulenta (7-6%, 501 bp, 487 bp), A. irregularis (8-7%, 509 bp, 505 bp), A. micropholis (5%, 502 bp, 488 bp), and A. reticulata heterochilus (7-6%, 521 bp, 505 bp).

Natural history.

We found the holotype at night. It was slowly moving along the steep slope of the bank of a small rocky creek in primary lowland evergreen rainforest (Fig. 6). When handled, the snake first tried to hide its head below body loops; the head was bend down at an almost right angle and with fangs partly visible outside of the mouth. In this head position, the snake repeatedly tried to strike. Either it tried to move slowly away from the human observers or it abruptly coiled and uncoiled, often jumping distances equaling almost its entire body length, similar to wolf snakes of the genus Lycophidion ( Rödel et al. 1995; Greene 1997). The two snakes from south-eastern Guinea were collected in plantations of banana, manioc and coffee, which were planted under the few remaining high trees of the former forest. No other data on biology and ecology of the new species are known.

Distribution.

So far the new species is known from the type locality and two additional sites in south-eastern Guinea. These latter two sites are about 27 km apart (Fig. 7).

Etymology.

We name this new snake to honor our recently deceased friend and colleague, William Roy “Bill” Branch, for his outstanding contributions to African herpetology. MOR and OSGP are particularly pleased to name the species in memory of Bill. We remember our outstanding field trips with him, unforgettable discussions with a large portion of special humor, and his friendship. The dedication of this species of stiletto snake to Bill is particularly appropriate. After Bill turned from cancer research to herpetology (see "William R. Branch" in Li Vigni 2013), the subject of his first herpetological research, on the serotaxonomy and hemipeneal morphology of stiletto snakes, was presented in two contributions at a symposium of herpetology and ichthyology in Kruger National Park in 1975 ( Branch 1975a, b). As the vernacular name, we suggest Branch’s Stiletto Snake.