Thursday, March 7, 2019

[Herpetology • 2019] Atractaspis branchi • A New Stiletto Snake (Lamprophiidae, Atractaspidinae) from Liberia and Guinea, West Africa

Atractaspis branchi 
Rödel, Kucharzewski, Mahlow, Chirio, Pauwels, Carlino, Sambolah & Glos, 2019

Branch’s Stiletto Snake  ||  DOI: 10.3897/zse.95.31488

We describe a new stiletto snakeAtractaspis, from western Liberia and southeastern Guinea. The new species shares with morphologically similar western African Atractaspis species, A. reticulata and A. corpulenta, the fusion of the 2nd infralabial with the inframaxillary. From A. corpulenta the new species differs by a more slender body (276–288 ventrals and 19 or 20 dorsal scale rows versus 178–208 ventrals with 23–29 dorsal scale rows), a divided anal plate and divided subcaudal scales (both non-divided in A. corpulenta). The new species differs from most A. reticulata by having 19 or 20 dorsal scale rows at midbody (versus 21–23, rarely 19), and a lower ventral count (276–288 versus 304–370). The new species thus has a relatively longer tail: snout-vent-length / tail-length in the female holotype (15.7) and paratype (21.5) versus a mean of 23.6 in seven female A. reticulata. The new Atractaspis likely is endemic to the western part of the Upper Guinea forest zone and thus adds to the uniqueness of this diverse and threatened biogeographic region.

Key Words: Biodiversity hotspot, biogeography, rainforest, Reptilia, Squamata, species delimitation, Upper Guinea forest

Figure 1. Life coloration of the Atractaspis branchi sp. n. holotype (ZMB 88529). 

Figure 3. Holotype of Atractaspis branchi sp. n. (ZMB 88529) 1 head scalation in dorsal (a), lateral (b), and ventral (c) views 2 ct-scan of skull in dorsal (a), lateral (b), and ventral (c) views; lower jaw virtually removed; green: pterygoid, yellow: palatine, orange: vomer. Scale bar: 1 mm.

Atractaspis branchi sp. n.

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.

Figure 6. Type locality of Atractaspis branchi sp. n. in north-western Liberia. The holotype specimen was found at night. It was moving along the steep slope on the left bank of the small creek.

 Figure 7. Localities of Atractaspis branchi sp. n. and A. reticulata ssp.
Records are based on museum specimens, literature and database (GBIF) records; large closed symbols represent the type localities of the different taxa, stars: A. branchi sp. n., circles: A. reticulata records without reference to subspecies; triangles: A. r. reticulata; quadrats: A. r. heterochilus; diamonds: A. r. brieni; country borders indicted as white lines; background of map: major biomes based on Olson et al. (2001).

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.

 Mark-Oliver Rödel, Christoph Kucharzewski, Kristin Mahlow, Laurent Chirio, Olivier Pauwels, Piero Carlino, Gordon Sambolah and Julian Glos. 2019. A New Stiletto Snake (Lamprophiidae, Atractaspidinae, Atractaspis) from Liberia and Guinea, West Africa. Zoosystematics and Evolution. 95(1): 107-123.  DOI: 10.3897/zse.95.31488