Caecum knysnaense Vannozzi & Pizzini & Raines 2015, sp. n.
Creators: name: Vannozzi, Angelo
name: Pizzini, Mauro
name: Raines, Bret
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Littorinimorpha
Caecidae
Caecum
Caecum knysnaense

description: Caecum knysnaense sp. n.
Figs 5A–E, 7, 22I, 23I, 24B, 25P
Etymology: Derived from the type locality.
Description: Tube subcylindrical, with a slight dextral torsion, evenly arched. Tube smooth, glossy, colourless, semitransparent. Aperture with a barely visible swelling, strongly oblique toward the ventral side, preceded by a white band. Surface with only fine oblique growth lines. Septum smooth, dome­shaped, protruding, with an ear­like mucro directed halfway between the dorsal and the right side. Macula large, with a frosted appearance, formed by two oblong bands fused in the middle. Juveniles rather similar to the adults, showing a narrower and more arched shape of the tube. Periostracum light brown. Operculum flat with a raised internal nucleus and internally thickened edge. Outer side showing a spiral of about three whorls. Larval stage unknown.
Length: 1.2–1.9 mm.
Type locality: SOUTH AFRICA: Western Cape: Knysna, Gericke Point, Sedgefield.
Holotype (Figs 5A–C, 22I, 23I): SOUTH AFRICA: Western Cape: lv, Knysna, Gericke Point, Sedgefield (NMSA S7625 /T3362), length 1.6 mm, min. diam. (posterior end) 0.31 mm, diam. in the middle of the tube 0.36 mm, max. diam. (apertural end) 0.37 mm.
Paratypes: SOUTH AFRICA: Western Cape: 1 lv and 6 sh, same data as holotype (NMSA W9673 /T3364); 2 lv and 6 sh (1 juv), Walker’s Point, W of Knysna, leg. J.P. Marais iii.1991 (NMSA W9672 /T3363).
Doubtful: SOUTH AFRICA: Western Cape: 1 sh (broken), Walker’s Bay, W of Knysna, iii.1991 (JPM).
Comparative material examined: C. macrum van der Linden & Moolenbeek, 2000, SENEGAL: 2 sh, Charbonnier, petite épave, - 34 m, fond sable coquiller légerement vaseux, leg. J. Pelorce (MP); 1 sh, Somone, - 7 m, sable sur rochers plats avec curvettes sable, leg. J. Pelorce (MP).
Distribution: Known with certainty only from Knysna (Fig. 7).
Remarks:This species clearly resembles Caecum austrafricanum sp. n. However, there are some consistent differences that set specimens of this species apart from the hundreds of C. austrafricanum specimens found in the same sites. In fact, C. knysnaense sp. n. is smaller and shows an aperture which is more oblique by ca. 10° and lacks a clear swelling. Additionally, the septum of C. knysnaense is convex while in C. austrafricanum it is typically flat or S­shaped.Also the mucro and the general aspect of the tube are different. Caecum knysnaense also strongly resembles C. macrum van der Linden & Moolenbeek, 2000 (Fig. 25R), from which it can be distinguished by the different shape of the mucro and by the more oblique aperture. Also the macula is different, being shorter and heartshaped in C. macrum (Fig. 24B, H).
description: Published as part of Vannozzi, Angelo, Pizzini, Mauro & Raines, Bret, 2015, Revision of South African Caecidae (Mollusca: Gastropoda), pp. 99 in African Invertebrates 56 (1) on pages 107-108, DOI: 10.5733/afin.056.0109, http://zenodo.org/record/7661863