Psammophis cornusafricae, Šmíd & Fernández & Elmi & Mazuch, 2023

Smid, Jiri, Fernandez, Sergio Matilla, Elmi, Hassan Sh Abdirahman & Mazuch, Tomas, 2023, Diversity of Sand Snakes (Psammophiidae, Psammophis) in the Horn of Africa, with the description of a new species from Somalia, Zoosystematics and Evolution 99 (2), pp. 345-361 : 345

Psammophis cornusafricae sp. nov.

Psammophis English name: African Horn Sand Snake Somali name: Subxaanyo [pronounced Subhanyo]; a term in the Somali language that refers to all Psammophis species that occur in the region. All Subxaanyo are believed to be harmless and friendly by the locals and are an important part of their folklore

Chresonymy.

Psammophis biseriatus in Calabresi (1927; in part), Scortecci (1939a), Scortecci (1939b), Lanza (1983; in part), Regnoli et al. (2003; in part);

Psammophis biseriatus tanganicus in Loveridge (1940; in part), Lanza (1990; in part);

Psammophis tanganicus Largen and Ramussen (1993; in part), Brandstätter (1996; in part), Largen and Spawls (2010; in part), Wallach et al. (2014; in part), Boundy (2020; in part);

Psammophis sp. in Vidal et al. (2008), Trape et al. (2019), Keates (2021).

Type material.

Holotype: MVZ:Herp:242772 (sample code TP28431; Fig. 6 ), subadult, sex unknown; Somalia, Bari Region, Heela Spring, 11 km NW (by road) of Baargaal (11.371°N, 51.0412°E), elevation 77 m above sea level; collected by T. J. Papenfuss on June 29, 2003.

Paratype: MVZ:Herp:242773, adult, sex unknown; same collection data as holotype.

Other material.

NMP-P6 V 76373 (sample JIR510; Fig. 7 ; MorphoBank accessions: M851260-M851339), subadult female (sex confirmed by genetics); Somaliland , 8.5 km S of Yuffleh (10.3°N, 47.182778°E), elevation 1758 m above sea level; collected by T. Mazuch on September 5, 2017 .

Diagnosis.

A Psammophis species sister to P. tanganicus , with the following combination of morphological characters: 11 infralabials; 9 supralabials, three of which are in contact with the eye; nostril pierced between two equal sized nasals; 15 anterior dorsals; 14-15 midbody dorsals; 11 posterior dorsals; 146-158 ventrals; 95-100 subcaudals. Body brown, grey or beige with only a faintly visible pale vertebral stripe but with well pronounced dorsolateral orange stripes on each side of the body. Tail with only a slight trace of or completely lacking any dark vertebral stripe; the posterior half of the tail uniformly pale yellow. Venter white to yellowish with a conspicuous stipple of irregular dark smears. Head dorsally with a symmetrical pattern of brown markings outlined by black margins which contrast with the grey or beige background coloration. Labials white with dark margins forming a black lip. Dark brown temporal stripe outlined by black blotches and stretching from the eye to the posterior end of the head.

Description of the holotype

(Fig. 6 ). SVL 42.6 mm, TL 20.3 mm (the very tip of the tail is missing; the original tail was hence probably a few millimeters longer), total length 62.9 mm.

Head flattened dorsoventrally, separated from the body by a distinct neck; nostril pierced between two nasals, major sector-shaped ( ‘pac-man’ -like shape); eyes large, with a round pupil; rostral roughly heptagonal, with a distinct groove at the base for flicking the tongue out; rostral visible from above and followed dorsally by one pair of internasals, one pair of prefrontals, a long and narrow frontal with nearly equally as long supraoculars to its side; preoculars in narrow contact with the frontal and wedged between the prefrontals and supraoculars; large pair of parietals contacted laterally by large anterior temporals, posterior temporals and enlarged postparietals. The temporal formula of the anterior temporal + posterior temporal scales is 1+3. Laterally, rostral followed by two consecutive nasals, an elongated loreal and a large preocular that forms the anterior margin of the eye. Two postoculars at the posterior eye margin, the upper of which being contacted by the parietal and the lower by the anterior temporal. Nine supralabials, of which the 4th, 5th and 6th are in contact with the eye; 11 infralabials, five of which are in contact with the anterior pair of chin shields. Two pairs of chin shields. Four (right side) and five (left side) gulars in a longitudinal row between chin shields and preventrals. Anterior dorsals 15, midbody dorsals 14, posterior dorsals 11; 158 ventrals; 85 subcaudals.

Coloration in preservation: body brownish beige, dorsum darker than the flanks, with dark sets of three to five dorsolateral scales separated by two to three paler scale rows. The frontal and supraoculars with dark pigment patches at their anterior sides, posterior margins pale. Parietals with dark oblong blotches by the medial line and at the anterior margin of the scales. Internasals and prefrontals dark to the sides and paler medially, which forms a narrow white-yellowish stripe at the nose tip. Supralabials white with contrasting dark brown upper and lower margins. The white of the supralabials continues onto the sides of the neck. Throat with extensive dark spots arranged in longitudinal stripes - one on each side of the mouth on the lower side of the infralabials up to the 6th infralabial, one at the mid-line running through the chin shields and gulars further on the belly.

Comparisons.

Psammophis cornusafricae sp. nov. can be differentiated from other congeners that occur in the Horn of Africa as follows: from its sister species P. tanganicus (character in brackets) by having 3-5 gulars in a longitudinal row between chin shields and preventrals (versus 2-3), posterior tip of the frontal moderately pointed (versus rounded), by lacking a clear orange or brownish dorsal stripe along the body and tail (versus orange vertebral stripe present), tail lacking a stripe, or having only a weakly developed dark vertebral stripe (versus tail with a clear dark vertebral stripe), having a clearly demarcated narrow temporal stripe on the head (versus broad stripe without clear demarcation), dark markings on the head dorsum paired and not fused (versus dark marking on the back of the head fused into a ‘W’ shape); from P. biseriatus (character in brackets) by having three supralabials in contact with the eye (versus two), usually one large anterior temporal (versus two), gular region strongly pigmented with dark longitudinal stripes (versus weakly pigmented with small dark spots), head ornately patterned above (versus uniformly colored), tail with absent or only a weakly developed dark vertebral stripe (versus tail with a clear dark vertebral stripe). Further morphological comparisons between P. cornusafricae sp. nov., P. tanganicus , and P. biseriatus are summarized in Table 2 .

From the other Horn species P. cornusafricae sp. nov. differs by having a lower number of midbody dorsals (14-15 versus 17 or 19 in P. aegyptius , P. lineatus , P. mossambicus , P. orientalis , P. punctulatus , P. rukwae , P. schokari , P. sudanensis a P. cf. sudanensis , P. trivirgatus ), or a higher number of midbody dorsals (11 in P. angolensis , 13 in P. pulcher ).

Variation.

The studied specimens of P. cornusafricae sp. nov. show some degree of morphological variation (Table 2 ). Namely, the number of infralabials varies between 10-11 and the number of supralabials between 8-9. The 3rd-5th supralabials are in contact with the eye in specimen NMP-P6V 76373 (the one with 8 supralabials); in the other two specimens it is the 4th-6th supralabials that touch the eye. Specimen NMP-P6V 76373 has three postoculars at the posterior eye margin and two anterior temporals (versus two postoculars and one anterior temporal in the other two specimens). Specimens MVZ:Herp:242773 and NMP-P6V 76373 (unilaterally) have two posterior temporals (versus three in the holotype). There are 14 midbody dorsals in the holotype, while the other two specimens have 15. The number of ventrals and subcaudals varies between 146-158 and 85-100, respectively. The two specimens examined genetically are closely related (Fig. 4 ). They are 99.35% identical in the cyt b sequence (different in 7 out of 1087 bp), 98.63% identical in the ND4 (different in 9 out of 662 bp), and 99.75% identical in the c-mos (different in 1 out of 400 bp).

Etymology.

The species epithet indicates the geographic origin of the species and translates as "The Sand Snake of the Africa’s Horn". It is a noun in the genitive case that is derived from the Latin words for horn (cornu-us) and Africa (Africa-ae).

Distribution.

Our knowledge on the distribution of P. cornusafricae sp. nov. is very limited because it has so far been confirmed only from two localities. They are both located in Somalia; the type locality is at the very tip of the Horn of Africa (Puntland), the locality of specimen NMP-P6V 76373 lies in central Somaliland, some 440 km west-southwest from the type locality (Fig. 8 ). Puntland and the eastern part of Somaliland are the driest parts of the Horn of Africa. They receive less than 200 mm of precipitation annually ( Muchiri 2007), and are covered by sparse vegetation (ESA CCI Team 2017) and geologically formed by the so-called Karkar and Taleh formations that include limestones, dolomites, and gypsum ( Schreiber 1993; Quiroga et al. 2022). We assume P. cornusafricae sp. nov. to roughly match the extent of the Karkar and Taleh formations and adjoin the range of P. tanganicus from the east. This distribution pattern with central Somaliland being a contact zone of closely related taxa has already been confirmed for other taxa, e.g. Tomopterna ( Pyxicephalidae ), Hemidactylus ( Gekkonidae ), Heliobolus , Latastia , Pseuderemias ( Lacertidae ), Uromastyx , Xenagama ( Agamidae ), Echis ( Viperidae ) ( Arillo et al. 1965; Lanza 1990; Zimkus and Larson 2011; Wagner et al. 2013; Tamar et al. 2018; Spawls and Branch 2020; Šmíd et al. 2020; Spawls et al. 2023).

Figures

Figure 4. Maximum Likelihood phylogeny of the genus Psammophis based on a concatenated alignment of the cyt b, ND 4 and c-mos genes (2,149 bp in total). The clade containing P. biseriatus, P. tanganicus and P. cornusafricae sp. nov. is highlighted in pink. Codes of samples newly sequenced for this study are in red. Locality details and original references of all samples are given in Suppl. material 1. Branch support is given in the order SH-aLRT / UFBoot / Standard bootstrap / MrBayes posterior probability.

Figure 6. Holotype of Psammophis cornusafricae sp. nov. (MVZ: Herp: 242772).

Figure 7. Psammophis cornusafricae sp. nov. in life (specimen NMP-P 6 V 76373, sample JIR 510), with a close-up of the head in the upper left corner, and the habitat at the locality where the specimen was found (8.5 km S of Yuffleh, Somaliland) at the bottom.

Figure 8. Distribution of P. biseriatus, P. tanganicus and P. cornusafricae sp. nov. in the Horn of Africa. Localities sampled for the genetic analysis are shown along with sample codes. The background layer shows shaded relief and water bodies and drainages and was made with Natural Earth (www. naturalearthdata. com). The species range maps were derived from Roll et al. (2017, 2021), Spawls et al. (2023), and the findings presented in this study.