Caecum knysnaense, Vannozzi & Pizzini & Raines, 2015

Vannozzi, Angelo, Pizzini, Mauro & Raines, Bret, 2015, Revision of South African Caecidae (Mollusca: Gastropoda), African Invertebrates 56 (1), pp. 99-99 : 107-108

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 ).

Figures

Fig.5.Caecum knysnaense sp. n., SouthAfrica:(A–C) holotype, Knysna,Gericke Point,Sedgefield (NMSA S7625/T3362) — (A) right side, (B) ventral side, (C) microsculpture; (D, E) paratype, operculum, Walker’s Point, W of Knysna (NMSA W9672/T3363) — (D) inner side, (E) outer side. Scale bar = 1 mm (A, B); 200 µm (D, E); 50 µm (C).

Fig. 7. Distribution map of Caecum knysnaense sp. n. („), C. austrafricanum sp. n. (S) and C. intortum sp. n. (T). White symbol indicates the type locality.

Fig. 22. Detail of the septum of South and western African Caecum species (right side): (A–C) C. subquadratum Carpenter, 1859 — (A) Walker’s Point, W of Knysna (NMSA S3729), (B) Walker’s Point, W of Knysna (JPM), (C) juv, Langebaan Lagoon, Saldanha Bay (JPM); (D, E) C. morgan sp. n., Cape Morgan Lighthouse — (D) holotype (NMSA B7132/T3377), (E) paratype (NMSA W9676/ T3378); (F–H) C. austrafricanum sp. n., Algoa Bay — (F) holotype (NMSA W9655/T3349), (G) paratype (JPM),(H) paratype (juv) (JPM); (I) C. knysnaense sp.n., holotype, Knysna, Gericke Point, Sedgefield (NMSA S7625/T3362); (J) C. intortum sp. n., holotype, Walker’s Point, W of Knysna (NMSA W9668/T3358); (K) C. inhacaense Albano & Pizzini, 2011, Aliwal Shoal, off Umkomaas area (JPM); (L, M) C. incisum sp. n. — (L) holotype, Walker’s Point, W of Knysna (NMSA S3728/ T3355), (M) paratype, Knysna,Gericke Point, Sedgefield (NMSA W9661/T3357);(N, O) C.maraisi sp.n.—(N) holotype, Knysna, GerickePoint,Sedgefield (NMSA W9765/T3376),(O) paratype (juv), Fish R. mouth (between Port Alfred and East London) (JPM 2117); (P, Q) C. leilae sp. n. — (P) holotype, Mzamba (NMSA D3032/T3374), (Q) paratype, Umtamvuna R. mouth (NMSA V3999/ T3884); (R) C. cf. glabrum (Montagu, 1803), Knysna, Gericke Point, Sedgefield (NMSA W9658); (S, T) C. glabrum (Montagu, 1803) — (S) Porto Mindelo, Ilha de São Vicente, Cape Verde (MP), (T) St. Malo, France (MP). Scale bar = 100 µm.

Fig. 23. Detail of the septum of South and western African Caecum species (ventral side): (A–C) C. subquadratum Carpenter, 1859 — (A) Walker’s Point, W of Knysna (NMSA S3729), (B) Walker’s Point, W of Knysna (JPM), (C) juv, Langebaan Lagoon, Saldanha Bay (JPM); (D, E) C. morgan sp. n., Cape Morgan Lighthouse — (D) holotype (NMSA B7132/T3377), (E) paratype (NMSA W9676/ T3378); (F–H) C. austrafricanum sp. n., Algoa Bay — (F) holotype (NMSA W9655/T3349), (G) paratype (JPM); (H)paratype (juv) (JPM); (I) C. knysnaense sp.n., holotype, Knysna, Gericke Point, Sedgefield (NMSA S7625/T3362); (J) C. intortum sp. n., holotype, Walker’s Point, W of Knysna (NMSA W9668/T3358); (K) C. inhacaense Albano & Pizzini, 2011, Aliwal Shoal, off Umkomaas area (JPM); (L, M) C. incisum sp. n. — (L) holotype, Walker’s Point, W of Knysna (NMSA S3728/ T3355), (M) paratype, Knysna, Gericke Point, Sedgefield (NMSA W9661/T3357);(N, O) C. maraisi sp.n.— (N) holotype, Knysna, Gericke Point,Sedgefield (NMSA W9765/T3376), (O) paratype (juv), Fish R. mouth (between Port Alfred and East London) (JPM 2117); (P, Q) C. leilae sp. n. — (P) holotype, Mzamba (NMSA D3032/T3374), (Q) paratype, Umtamvuna R. mouth (NMSA V3999/ T3884); (R) C. cf. glabrum (Montagu, 1803), Knysna, Gericke Point, Sedgefield (NMSA W9658); (S, T) C. glabrum (Montagu, 1803) — (S) Porto Mindelo, Ilha de São Vicente, Cape Verde (MP), (T) St. Malo, France (MP). Scale bar = 100 µm.

Fig. 24. Ventral side of South and western African Caecum species: (A) C. austrafricanum sp. n., paratype, Walker’s Point, W of Knysna (NMSA W9656/T3351); (B) C. knysnaense sp. n., paratype, Knysna, Gericke Point,Sedgefield (NMSA W9673/T3364);(C, D) C. intortum sp.n.— (C)paratype,Walker’s Point, W of Knysna (NMSA W9669/T3360), (D) the same specimen slightly rotated, detail of the macula; (E, F) C. leilae sp. n. — (E) paratype, Mzamba, near Natal border (JPM 2119), (F) the same specimen, detail of the macula; (G) C. inhacaense Albano & Pizzini, 2011, Mzamba, near Natal border (JPM 2119); (H) C. macrum van der Linden & Moolenbeek, 2000, Charbonnier, Senegal (MP); (I) C. crassum de Folin, 1870, Banc d’Arguin, Mauritania (MP). Scale bar = 1 mm (A–C, E, G–I); 300 µm (D, F).

Fig. 25. South and western African Caecum and Parastrophia species: (A) P. avaricosa sp. n., holotype, Mzamba (NMSA E1665/T3354); (B, C) P.ornata sp. n., Mzamba,near Natal border — (B) holotype (NMSA W9677/T3379), (C) paratype (JPM 2119); (D) C. sepimentum de Folin, 1868, Kosi Bay (NMSA S2010); (E) C. cf. oahuense Pilsbry, 1921, Aliwal Shoal, off Umkomaas area (JPM); (F) Caecum cf. gulosum Hedley, 1899, Kosi Bay (NMSA S2869); (G, H) C. succineum de Folin, 1880 — (G) between Bhanga Nek andKosi Bay (NMSAS1586), (H)Aliwal Shoal, off Scottburgh (NMSA W9684); (I) C. cf. glabrum (Montagu, 1803), Knysna, Gericke Point, Sedgefield (NMSA W9658); (J) C. glabrum (Montagu, 1803), Rabat, Morocco (MP); (K) C.lindae sp. n., holotype, Cape Morgan Lighthouse (NMSA W9682/T3924); (L, M) C. cf. musorstomi Pizzini, Raines & Vannozzi, 2013, Landers reef (JPM); (N, O) C.austrafricanum sp.n., paratypes,Walker’s Point,W of Knysna (NMSA W9656/T3351);(P) C.knysnaense sp.n., paratype,Knysna,Gericke Point,Sedgefield (NMSAW9673/ T3364); (Q) C. intortum sp. n., paratype, Walker’s Point, W of Knysna (NMSA W9669/T3360); (R) C. macrum van der Linden & Moolenbeek, 2000, Charbonnier, Senegal (MP); (S, T) C. crassum de Folin, 1870, Gabon (MP): (S) adult; (T) juvenile. Scale bar = 1 mm.