Prosymna confusa, Conradie & Keates & Baptista & Lobón-Rovira, 2022

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 confusa sp. nov.

Figs 6 , 7 , 8 , 9 , 13 Common names: Plain Shovel-snout Snake (English); Cobra-de-focinho-de-pá-lisa (Portuguese).

Chresonymy.

Prosymna angolensis : Bogert 1940: 59; Monard 1937: 123 (in part); Broadley 1980: 152 (in part).

Prosymna ambigua : Branch 2018: 64, fig. 24; Pietersen et al. 2021: 96, fig.

Monard (1937) was the first to document a uniformly grey specimen from Ebanga. This was followed by Bogert (1940) who documented a specimen from Capelongo (AMNH R50504) that also exhibited a uniform pale brown dorsum with small white spots (similar to P. meleagris pattern). This uniform dorsum colouration is in agreement with the new specimen collected from coastal Angola ( Branch 2018) and this colouration is very distinct from the other two species, yellowish grey with paired small black dorsum spots in P. angolensis and bright yellow with fused black blotches in P. lisima sp. nov.

Material examined.

Holotype (female). PEM R24013 , collected from 20 km west of Lola on the road northwest to Camacuio, on the edge of Bentiaba River (-14.27583, 13.45806, 791 m a.s.l.), Namibe Province, Angola by William R. Branch, Pedro Vaz Pinto and João S. de Almeida on 2 November 2015.

Additional material tentatively assigned to the new species.

AMNH 50504, Capelongo, approx. -14.46645, 16.29241, Huíla Province, Angola ( Bogert 1940: 59); Ebanga, approx. -12.73333, 14.73333, Benguela Province, Angola ( Monard 1937: 123) .

Diagnosis.

The new species differs from other Prosymna species in the following characters: rostral sharply depressed and angular (vs. rounded in P. visseri ); presence of a single band-like internasal (vs. paired internasals in P. somalica , P. bivittata , P. sundevalli , P. lineata ); dorsal scales smooth (keeled in P. janii ); midbody scale rows 15-17 (vs. 19-21 in P. pitmani ); six supralabials, with 3rd and 4th entering orbit (vs. five supralabials, with 2nd and 3rd entering orbit in P. meleagris and P. greigerti ); single apical pits on dorsal scales (vs. paired apical pits in P. ruspolii ); lower number of ventral scales in both sexes (116-129 vs. 153-199 in P. frontalis ); dorsum uniform dark grey (vs. scarlet head and dark body in P. ornatissima ). It further differs from its closest congeners in the Prosymna angolensis group: one postocular (vs. two in P. lisima sp. nov.), dorsum uniform grey (vs. dorsum with large mostly fused black blotches in P. lisima sp. nov. and mostly smaller paired longitudinal rows of grey to black spots in P. angolensis ), postorbital bone absence (vs. present in P. lisima sp. nov.), presence of two well-develop palatine teeth (vs. four to five in P. lisima sp. nov. and three reduced teeth in P. angolensis ), fused braincase (vs. unfused in P. angolensis and P. lisima sp. nov.) and two frontal foramina (vs. three to four in P. angolensis and P. lisima sp. nov.).

Etymology.

When the late Bill Branch collected the holotype, he was unsure of its identification and referred to it as an unusual specimen that could not be assigned to any known species from Angola. He later referred to it as P. ambigua ( Branch 2018), presumably based on its uniform grey colouration. The name confusa is a reflection of the confusion this specimen has caused and of the general confusion in the P. angolensis group.

Description of holotype

(Fig. 13 ). Adult female measuring 240 mm SVL+29 mm TL = 269 mm total length. The body is cylindrical and elongated, tapering gradually to a very short tail, 10.8% total length, tail tip with prominent spike. Dorsal scales smooth, with single apical pits, in 17-15-15 scale rows, scale row reduction from 17 to 16 take place at ventral number 29 with the fusion of 3rd and 4th dorsal scale row on right side and from 16 to 15 at ventral 32 with the fusion of 3rd and 4th dorsal scale row on left side; 151 ventral scales; cloaca entire; 26 subcaudal scales. Head in dorsal view (Fig. 13B ): head narrow and rounded, barely wider than ‘neck’; rostral clearly visible from above, much broader than long (2.84 × 1.47 mm); a single narrow internasal, which is much longer than wide (2.40 × 0.57 mm) and in broad contact with the rostral anteriorly, posteriorly in broad contact with prefrontal and laterally with nasals; single band-like prefrontal which is longer than wide (3.71 × 1.25 mm), in contact laterally with loreal and posteriorly with the frontal and supraocular scales; frontal pentangular, almost as long as wide (2.97 × 3.14 mm), nearly equal in length to the distance to snout (2.91 mm), more than double than prefrontal width (3.14 vs. 1.25 mm), and three quarters the length of the parietals (3.14 vs. 2.43 mm), in contact laterally with narrow supraoculars, and posteriorly with two very large parietals; paired parietals longer than wide (2.28 × 2.43 mm), in contact posteriorly with each other and laterally with temporals. Head in ventral view (Fig. 13C ): rostral clearly visible from below, protruding well past jawline; mental small, triangular; infralabials eight on right side and nine on left side, first three in contact with single paired chin shields, 1st infralabials in contact with each other; additional three rows of smaller gular scales present before the start of ventral scales. Head in lateral view (Fig. 13D ): snout sharply pointed, longer than the horizontal diameter of eye (ED/SL = 0.45); rostral large with acutely horizontal angular edge, excavated below; nostril is oval shaped, piercing divided nasal, and directed backwards; nasal scale longer than wide, with anterior part in full contact with rostral, posterior lower corner in contact with 1st supralabial, upper section in contact with internasal scale and prefrontal and posteriorly with loreal and prefrontal; nasal suture present and intersecting loreal; single small loreal as long as wide (0.84 × 0.84 mm), in contact below with 1st and 2nd supralabial, above with prefrontal, anteriorly with nasal and posteriorly with single preocular; single preocular on both sides in contact anteriorly with loreal and above with supraocular and prefrontal, posteriorly with loreal; eye large 16.50% HL, vertical diameter (1.53 mm), two thirds as deep as distance between eye and lip (0.42); pupil round; one postoculars, in contact with 4th upperlabial, 1st temporal scale, supraocular, and parietal; temporals 1+2; narrow elongated supraocular in contact anteriorly with preocular and prefrontal, posteriorly with the postocular and above with frontal; five supralabials on both sides with 3rd and 4th in contact with eye on right and 2nd, 3rd and 4th on left, 5th and 6th supralabial the largest.

Colouration. In life (Fig. 6 ). Dorsum uniform grey with the anterior edges of scales with a white spot, outermost two to three scale rows white, with only the first outermost scale row of tail white. Nape with a faint collar that is three scale rows wide. The prefrontal and internasal black compared to the rest of the head being grey. Eye black. Ventrum white. In preservative (Fig. 13 ). Same as in life, but the grey faded and became brown. Ventrum beige.

Additional material variation. See Table 2 for summarised meristic data. Only data of three females were available, but the assignment of historical material to P. confusa sp. nov. still requires confirmation. Dorsal scales smooth and in 17-17-15 rows at midbody; 143-155 smooth ventral scales; 17-26 paired subcaudal scales; one preoculars; one postoculars; temporals 1+2; five or six supralabials, with 3rd and 4th entering the orbit; seven infralabials, with first three in contact with the 1st chin shield, cloacal scale entire. Largest female: 240+29 mm (holotype PEM R24013). The colouration is similar to the holotype, except that in the Capelongo specimen (AMNH R50504) the white spots are much more conspicuous (Fig. 14 ). The specimen from Ebanga is unaccounted for ( Broadley 1980), but Monard (1937) described the colouration as uniform grey above.

Skull osteology and teeth (Figs 7 - 9 ). The holotype presents a compact and rigid skull common among Prosymna species with fused braincase, fused parietal, and unfused frontal and nasal bones. Postorbital bone is absent. Parietal with a fronto-lateral sharp edge that participates virtually as posterior edge of the orbital rim. Premaxilla has a well-developed and robust ascending nasal process that lies between the ventral laminae of the nasals with low profile of the anterior portion which gradually slope to a narrow tip and two elongated maxillary process in contact with the maxilla. Nasal bones are medium large bones in contact with frontal and premaxilla. Septomaxilla is a well-developed bone, in broad contact with premaxilla, frontal, vomer, prefrontal and frontal bone. The vomer is well developed with performed dorsolateral portion of the bone. Maxillary is reduced anteriorly with an elongated pick-shaped palatine process with six to seven laterally reduced curved tooth loci, followed by four to five enlarged lancet-shaped tooth loci. Palatine with two well developed teeth and an enlarged dorsal and curved vomerine process. Pterygoid is a thin elongated bone. Supratemporal is in broad contact with the quadrate and participates in the lateral movement of the lower jaw. The lower jaw is comprised of compound, splenial, coronoid, and dentary bones. Coronoid and splenial bones are reduced, almost vestigial. Dentary bone with six tooth loci.

Hemipenis . Unknown. Bogert (1940) suggested it to be similar to P. ambigua . However, Prosymna ambigua is unique in having a very long ‘telescopic’ hemipenis that is longer than the tail, which is not present in the Prosymna sundevalli group ( Broadley 1980). The latter group, to which P. confusa sp. nov. belongs, is characterised by its short hemipenes (8-10th ventral scales long vs. longer than tail in P. ambigua ), low number of flounces (5-6 vs. more than 50 in P. ambigua ) and straight retractor muscle (telescopic in P. ambigua ). Prosymna frontalis shares a similar hemipenile structure with P. ambigua .

Natural history notes.

The holotype was found actively moving around near a large rock outcrop during the day.

Distribution and habitat.

This species is endemic to southwestern Angola (Fig. 2 ), and appears to be associated with Colophospermum mopane woodlands, dry savannas, and semi-desert shrublands ( Barbosa 1970). The new specimen was found in sandy plains with scattered low granite outcrops, with varying degrees of short grass cover and scattered bushes. Vegetation included Colophospermum mopane , Ficus sp., Senegalia (= Acacia ) mellifera, Commiphora sp., Boscia foetida , and Salvadora persica . The two additional historical specimens from Ebanga and Capelongo that are tentatively assigned to this species occurred in similar dry habitat.

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 6. Live P. confusa sp. nov. (PEM R 24013) from 20 km west of Lola on the road northwest to Camacuio and on the edge of Bentiaba River, Namibe Province, Angola (Photo: Bill Branch).

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 13. Holotype of Prosymna confusa sp. nov. (PEM R 24013) from 20 km west of Lola on the road northwest to Camacuio and on the edge of Bentiaba River, Namibe Province, Angola A dorsal and ventral full body B dorsal head C ventral head D lateral head.

Figure 14. A specimen (AMNH 50504) form Capelongo, approx. - 14.46645, 16.29241; Huila Province, Angola, assignable to the new species, P. confusa sp. nov. (Photos: Lauren Vonnahme, American Museum of Natural History).