Xerocrassa (Xerocrassa) lacertara (Bourguignat, 1863)

Ezzine, Issaad Kawther, Pfarrer, Beat, Dimassi, Najet, Said, Khaled & Neubert, Eike, 2017, At home at least: the taxonomic position of some north African Xerocrassa species (Pulmonata, Geomitridae), ZooKeys 712, pp. 1-27 : 6-9

Xerocrassa (Xerocrassa) lacertara (Bourguignat, 1863) Figs 2, 7

1863 Helix lacertarum Bourguignat Malacologie de l’Algérie, I: 209 [Plaines entre Djelfa et El-Aghouat (de la Péraudière)].

1863 Helix lacertarum var. minor Bourguignat Malacologie de l’Algérie, I: 209 [collines d’Ogla-Zemera, à 10 lieues nord-ouest de Bou-Saâda ( Marès)].

1898 Helix lacertarum , Pallary, Comptes rendu de l’association française pour l’avancement des Sciences [Saint-Etienne], 26 (2) [1897]: 557.

Type specimens.

lacertarum : Syntypes MHNG-MOLL 114001/5; minor : syntype MHNG-MOLL 114006/1.

Additional specimens.

"Djebel Sahari près de Djelfa (34.6743°N 3.2552°E) MHNG-MOLL 114003/10; "entre le rocher du Sel et Mesram" (34.8375°N 3.0921°E) MHNG-MOLL 114004/8; "entre Aïn Ouessera et Bou Ghezoul" (35.5819°N 2.8992°E) MHNG-MOLL 114005/11; “Aïn-Seba, près de Bousaada" (35.2118°N 4.1763°E) MHNG-MOLL 114007/1. - Localities mentioned in the synonymy of X. latastei , but not represented in Bourguignat’s collection: "Ouled Naïl près de Biskraoù” (34.8370°N 5.75104°E); “à Aïn-Gussera” (= Ain Oussera 35.4495°N 2.9045°E); “à Bou Ghezoul sur les hauts plateaux" (= Boughezoul 35.6992°N 2.8482°E); "entre Boghar et Laghouat" (34.7554°N 3.1747°E) "et entre cette ville et Djelfa" (34.2577°N 3.0998°E). - unclear: MHNG-MOLL 114002/1, Saïda (pr. Oran); MHNG-MOLL 114008/1 Sebdou (pr. Oran).

Description.

Shell small, globular, basic colour creamy-whitish; protoconch very small, brownish, consisting of two whorls; teleoconch with many axial riblets, surface submalleate; whorls well rounded, with a moderately deep suture; last whorl with a single brown band at the periphery, often dissolved to a string of brown stripes; dark spots may occur usually irregularly spread all over the teleoconch, sometimes arranged in axial stripes; aperture semioval, with a small white lip; peristome small, sharp; umbilicus narrow, nearly completely obscured by a reflection of the columellar callus.

Measurements (syntype). D: 11.8 mm; H: 10.1 mm; PD: 6.7 mm; PH: 5.63 mm; W: 5.75.

Distribution

(Fig. 2): Xerocrassa lacertara is hitherto only known from the collection of Bourguignat, and seems to live restricted to the arid areas in eastern Algeria.

Remark.

Deduced from its shell morphology, this species is close to X. latastei . Both species share the globular shell form, the glossy shell surface, the ribbing mode, and the colouration pattern. In the absence of preserved specimens, we used these criteria to classify this species within the genus Xerocrassa . It differs from X. latastei in size (smaller in X. lacertara ), in the umbilicus, which is more strongly covered in X. lacertara than in X. latastei , in the more pronounced ribbing pattern of the teleoconch whorls, and the missing granulation of the upper teleoconch (in X. latastei ), which is malleate in X. lacertara .

When describing X. latastei , Bourguignat mentioned some of the localities, where he recorded X. lacertara 34 years before. This proves that he had no clear concept of these two species. Looking to the distribution patterns, both species are separated by a large area (ca. 300 km as the crow flies) without any record of the one or the other species. This is not simply an artefact due to undersampling, because the southern part of the province of Constantine is relatively well represented in his collection. For this reason and the pronounced differences in shell morphology we keep these two taxa as separate species until preserved animals from Algeria can be studied.

There are two records for this species from western Algeria south of Oran in MHNG, but their presences in the area needs reconfirmation in order to avoid any mis-labelling in the museum. Pallary (1898) records the species from "sur les berges de l’O. Souag (= O. el Hammam), à 12 kilomètres S.-O. d’Aïn Fekan". These specimens were not seen by the authors, and thus their identity remains uncertain.