Xenocalamus mechowii Peters, 1881

Conradie, Werner, Baptista, Ninda L., Verburgt, Luke, Keates, Chad, Harvey, James, Júlio, Timóteo & Neef, Götz, 2021, Contributions to the herpetofauna of the Angolan Okavango-Cuando-Zambezi river drainages. Part 1: Serpentes (snakes), Amphibian & Reptile Conservation (e 292) 15 (2), pp. 244-278 : 262

Xenocalamus mechowii Peters, 1881

Elongate Quill-snouted Snake ( Fig. 22, Map 20) Material: PEM R23463, Quembo River source, Moxico Province, -13.13586° 19.04709°, ~ 1,440 m asl; PEM R23533, alive on road, West of Menongue, Cuando Cubango Province, -14.67794° 17.23322°, 1,368 m asl; PEM R27385, grasslands west of Luo River, Moxico Province, -13.72468° 21.69403°, 1,009 m asl. Description: Dorsal scales smooth and in 17 rows at midbody; 228–254 smooth ventrals; 27–28 paired subcaudals; 2 postoculars; 1 temporal; 6 supralabials, the 3 rd and 4 th entering the orbit; 5 infralabials, the first two in contact with the anterior chin shield; cloacal scale divided. Largest male: 438 + 40 mm (PEM R23533). Habitat and natural history notes: PEM R23463 had the remains of a Zygaspis nigra in its stomach. Comment: Broadley (1971) assigned material from western Zambia to a hybrid form between the two subspecies, X. m. mechowii and X. m. inornatus, due to scale counts overlapping with the two recognized subspecies. Our northernmost specimen has scalation within the range of X. m. inornatus (PEM R23463 and PEM R27385: 247 and 254 ventrals and 27 and 28 subcaudals), while our southern sample is in range of X. m. mechowi (PEM R23533: 228 ventrals and 28 subcaudals) and thus could also be allocated to these transitional populations. Recently, Portillo et al. (2018) used the material mentioned above and found no genetic differences between the two samples, but that study did not include material from the northern populations of the nominal form (i.e., outside of the purported hybrid zone). These inconsistencies in morphology coupled with low genetic divergence cast doubt on the validity of these two subspecies. Further investigation is needed to assess the validity of the taxa in question, but here we treat them by their binomial name.