Prosymna angolensis Boulenger, 1915

Conradie, Werner, Keates, Chad, Baptista, Ninda L. & Lobon-Rovira, Javier, 2022, Taxonomical review of Prosymna angolensis Boulenger, 1915 (Elapoidea, Prosymnidae) with the description of two new species, ZooKeys 1121, pp. 97-143 : 97

Prosymna angolensis Boulenger, 1915

Figs 4 , 7 , 8 , 9 , 10 Common names: Angolan Shovel-snout snake (English); Cobra-de-focinho-de-pá-de-Angola (Portuguese).

Chresonymy.1

Prosymna frontalis : Bocage 1873: 218, 1882: 288, 1895: 98; Boulenger 1894: 248, 1896: 641.

Prosymna ambigua : Monard 1931: 104, 1937: 123; Mertens 1937: 13.

Prosymna ambigua ambigua : Mertens 1938: 439; Loveridge 1958: 151.

Prosymna angolensis : Boulenger 1915: 208; Chabanaud 1916: 439; Monard 1937: 114, 122; Bogert 1940: 59; Mertens 1955: 94, 1971: 86; Hellmich 1957: 66; Loveridge 1958: 149; FitzSimons 1962: 161, 1966: 53, 1970: 104; Isemonger 1968: 129; Broadley 1980: 512, 1990: 227, 1995: 48; Auerbach 1987: 178; Branch 1998: 84, 2018: 64; Broadley et al. 2003: 187 (in part); Marais 2004: 236; Broadley and Blaylock 2013: 219; Herrmann and Branch 2013: 8; Wallach et al. 2014: 568; Baptista et al. 2019: 118; Chippaux and Jackson 2019: 283, Ceríaco et al. 2021a: 16 (in part).

When Boulenger (1915) described P. angolensis , he did not designate a precise type locality nor a type specimen for that matter. Later, Loveridge (1958) proposed designating Huíla as the type locality, but it was Broadley (1980) that finally restricted the type locality to Caconda by designating a lectotype of the material he examined on his visit to Museu Bocage, Lisbon (MBL), Portugal in 1968. The reasons for this change in the proposed type locality, were that the Huíla specimen was unaccounted for, as well as the Caconda material was in the best overall condition to represent the species. He initially designated MBL 1606b as the lectotype, but with the destruction of the MBL collection, he designated one of the remaining Caconda specimens in Naturhistorischen Museums in Wien (NMW 19275b) as the replacement neotype (see Gemel et al. 2019).

Material examined.

Neotype (Fig. 10 ). NHMW 19275:2, collected from Caconda (approx. -13.73537, 15.06720, 1662 m a.s.l.), Huíla Province, Angola . Neotype designated by Donald Broadley (1980). Additional material. MBL 1609, Angola (no precise locality) , Angola ; MBL 1605a, Bibala , Angola ; MBL 1605b, Bibala , Angola ; CHL 0521, Bicuar NP, Angola ; NMW 19275 :1, Caconda , Angola ; NMW 19275 :2, Caconda , Angola ; MBL 1606a, Caconda , Angola ; MBL 1606b (original lectotype), Caconda , Angola ; MBL 1606c, Caconda , Angola ; MBL 1608, Caconda, Angola; USBN 20035, Luanda, Angola ; CAS 84181 , Luanda, 3 mile S of airport, Angola ; MBL 1607, Maconjo = Maconge , Angola ; MCZ 32468 , Missao do Dondi Bela Vista , Angola ; MBL 1604, interior of Mossamedes , Angola ; UM 20178, Goeverega, Botswana; UM 21271, 15 km WSW of Katima Mulilo , Namibia ; SMF 46614 , Karakuwisa, Kavango, Namibia ; TM 55043, Katima Mulilo , Namibia ; UM 24204, Katima Mulilo , Namibia ; SAM ZR16574, Namutoni , Namibia ; NMZB 9532, NE of Waterberg , Namibia ; NMZB 13953, Inyokene, Nyamandhlovo , Zimbabwe ; NMZB 13787, Malinbdi Siding, Hwange , Zimbabwe ; NMZB 13788, Malinbdi Siding, Hwange , Zimbabwe .

General description.

See Table 2 for summarised meristic data. Dorsal scales smooth, arranged in 17-15-15 (rarely 19-15-15) rows at midbody, scale row reduction takes place between ventral scales 16-20 (males) and 14-49 (females); one (sometimes two or three on supracaudal scales) apical pits; 126-163 (126-155 males, 134-163 females) smooth ventral scales; 16-28 (22-28 males, 16-25 females) paired subcaudal scales; rostral is acutely angular horizontally; internasal is single and bandlike; 1 preocular; 1 (rarely 0 or 2) postocular; temporals mostly 1+2 (rarely 2+2, 2+3); mostly 6 supralabials, with 3rd and 4th entering the orbit (rarely 5 (2, 3) or 7 (3, 4)); 7 infralabials, with first 3 in contact with the chin shield (rarely 8 (3)), cloacal scale entire.

Skull osteology and teeth (Figs 7 - 9). Based on the examination of a single female specimen (SAM ZR16574, Namutoni, Namibia), P. angolensis presents a compact and rigid skull, which is common among Prosymna species. It has an unfused braincase and nasal bones. Parietals are fused and the fronto-lateral portion presents a sharp edge that forms the edge of the orbital rim. Postorbital bone is absent. Premaxilla has a reduced ascending nasal process with a small groove between the ascending process and frontal portion of the bone. Premaxilla lies between the ventral laminae of nasals with a high profile of the anterior portion which curves shapely to finish on a convex profile. Maxilla and premaxilla are in contact. Nasal bones are reduced and display a wing-shape with a narrower anterior portion. Septomaxilla is a well-developed bone, in broad contact with the premaxilla, frontal, vomer, prefrontal and frontal bones. Vomer well developed with perforated dorsolateral portion of the bone. Maxilla reduced anteriorly with an elongated pick-shaped palatine process, with seven or eight laterally reduced curved tooth loci, followed by four enlarged and lancet-shaped tooth loci. Palatine with three reduced teeth and an enlarged dorsal and curved vomerine process that reinforces the internal portion of the orbit. Pterygoid is a thin elongated bone. Supratemporal is an enlarged bone in broad contact with the quadrate and participates in the lateral movement of the lower jaw. The lower jaw consists of compound, splenial, coronoid, and dentary bones. Coronoid and splenial bones are reduced, almost vestigial. Dentary with eight or nine small sharp tooth loci, with first third clear of any teeth.

Colouration in life (Fig. 4 ). The head is yellowish-brown with variable darker black markings that can be absent. Most commonly there is an anterior black band across the frontal, followed by a pair of black blotches around the orbits, supraoculars and parietals. A distinct black nuchal spot or collar is often present. The dorsal colouration varies from having mostly small paired black longitudinal vertebral spots (similar to P. sundevalli ) to a speckled pattern (similar to P. lineata ) on a pale yellowish-brown to grey ground colour. Ventrum and outermost two or three dorsal scale rows yellowish white.

Hemipenis . Short hemipenis with a length that reaches the 9-10th ventral scales ( Broadley 1980).

Size. Males vary from 160-248 (208.7 ± 29.8) mm SVL and 22-30 (26.5 ± 2.7) mm TL, with the largest male measuring 248+28 = 276 mm (NMZB 9532, NE of Waterberg, Namibia). Females vary from 127-305 (224.7 ± 51.1) mm SVL and 12-27 (19.9 ± 3.7) mm TL, with the largest female measuring 305+22 = 327 mm (SMF 32541, Cubal, Angola). Bocage (1895) mentioned an unsexed individual (probably a female) that measured 331+29 = 360 mm, but this specimen was unaccounted for in MBL.

Natural history.

This is a semi-fossorial species that feeds exclusively on reptile eggs, using its blade-like rear maxillary teeth to puncture the eggs, similar to other Prosymna species.

Distribution and habitat.

Currently the species is known to occur in three main geographic clusters: west-central Angola, north-central Namibia and isolated records from the Zambezi Region in north-eastern Namibia, northern Botswana and north-western Zimbabwe (Fig. 2 ). However, it is possible that this distribution might be more continuous, given this is a rarely observed species that mostly emerges to the surface only after good rains ( Heinicke et al. 2020). The records from Luanda (USBN 20035 and CAS 84181) and northern Angola (IICT/R 14-1957) require verification. This species is associated with savanna with an annual rainfall of 500-1200 mm ( Broadley 1980). In southwestern Angola it has been found in miombo woodland in sandy soils ( Baptista et al. 2019). In the eastern Zambezi Region and northern Botswana, the species is associated with drier savanna in deep Kalahari sands ( Broadley 1980).

Localities.

Angola: Bela-Vista ( Missão do Dondi), -12.36667, 16.20000 ( Hellmich 1957: 66); interior of Benguela ( Bocage 1895: 98); Bibala, -14.76667, 13.36667 ( Bocage 1873: 218); Bicuar National Park, Woodland trapline 1, -15.09441, 14.83831 ( Baptista et al. 2019: 118); Caconda, -13.73537, 15.06720 ( Bocage 1895: 151); Cubal, -13.03333, 14.73333 ( Mertens 1938: 439); Ebanga, -12.73333, 14.73333 ( Monard 1937: 123); Huíla, -15.08333, 13.55000 ( Bocage 1895: 98); Luanda and 'Luanda, 3 mi S of airport’, -8.83333, 13.26667 ( Broadley 1980: 515); Maconjo, -15.016667, 13.2000 ( Bocage 1895: 98); interior of Mossamedes ( Bocage 1873: 218); Quibula, -12.28333, 14.68333 ( Bocage 1895: 98); Posto do Milando (-8.81667, 17.56667) ( Ceríaco et al. 2021a: 16). Quindumbo, -12.46667, 14.93333 ( Bocage 1895: 98); Quissange, -12.43333, 14.05000 ( Bocage 1895: 98); Tundavala, -14.82018, 13.404217 (Justin Nicolau photo). Botswana: Joverega (Geoverega), - 19.13333, 24.25 ( Broadley 1980: 515). Namibia: Grootfontein, -19.55012, 18.10965 (Francois Theart photo); Karakuwisa, -18.933333, 19.733333 ( Mertens 1955: 94); Katima Mulilo, -17.5, 24.266667 ( Broadley 1980: 515); Namutoni, -18.807624, 16.940288 ( FitzSimons 1962: 161); 15 km WSW of Katima Mulilo, -17.61448, 24.20593 2 ( Broadley 1980: 515); Otjozondjupa Region, -19.08800, 18.83300 (http://www.the-eis.com/atlas/?q=details/snake-record&occurrence_id=654386). Zimbabwe: Malindi Siding, Hwange, -18.74885, 27.01852 ( Broadley 1995: 48); Inyokene, Nyamandlovu, -19.93333, 28.06667 ( Broadley 1995: 48).

Figures

Figure 2. a Maximum likelihood (IQTREE) concatenated phylogeny with BI BEAST and BI MrBayes support overlain. Each of the species groups are demarcated by coloured vertical bars at the right margin b maximum likelihood (IQTREE) phylogenies (16 S and cyt-b) with gene-specific single-locus species delimitation analyses results overlain. The bars to the right of the phylogeny represent the putative taxa assignments for each analysis and the values beneath the bars denote the total number of putative taxa for each analysis.

Figure 4. Variation in dorsal colouration of nominotypical Prosymna angolensis A Tundavala, Huila Province, Angola (Photo: Justin R. Nicolau) B Grootfontein, Namibia (Photo: Francois Theart) C Bicuar National Park (CHL 0521), Huila Province, Angola (Photo: Ninda L. Baptista).

Figure 7. A Lateral B ventral C medial D dorsal views of skulls of Prosymna angolensis subgroup. Red arrows depict variation characters between the P. lisima sp. nov., P. angolensis, P. confusa sp. nov., P. cf. frontalis, and P. janii.

Figure 8. A Frontal and B posterior views of skulls, and C lateral, dorsal, medial and ventral view of jaw of Prosymna angolensis subgroup. Red arrows depict variation in characters between the P. lisima sp. nov., P. angolensis, P. confusa sp. nov., P. cf. frontalis, and P. janii.

Figure 9. A Dorsal, frontal and ventral view of premaxillae B medial, posterior and dorsal views of palatine; and C lateral, dorsal, and ventral view of maxilla in P. lisima sp. nov., P. angolensis, P. confusa sp. nov., P. cf. frontalis and P. janii (from left to right).

Figure 10. Neotype of Prosymna angolensis (NMW 19275: 2) from Caconda, Huila Province, Angola (Photos: Alice Schumacher, Natural History Museum Vienna).