Caecum incisum, 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 : 109-111

publication ID	https://doi.org/ 10.5733/afin.056.0109
publication LSID	lsid:zoobank.org:pub:2A9621F0-009E-4A25-A093-DD322B9EC120
DOI	https://doi.org/10.5281/zenodo.7662092
persistent identifier	https://treatment.plazi.org/id/FFCC3C66-8B53-4D69-A338-DAF7E91E0223
taxon LSID	lsid:zoobank.org:act:FFCC3C66-8B53-4D69-A338-DAF7E91E0223
treatment provided by	Felipe
scientific name	Caecum incisum
status	sp. nov.

Treatment

Caecum incisum View in CoL sp. n.

Figs 8A–F View Fig , 11 View Fig , 22L, M View Fig , 23L, M View Fig , 26C, D View Fig

Etymology: From the Latin adjective incisus (incised) due to the presence of collabral incisions that are observed throughout the tube.

Description: Tube cylindrical, evenly arched, smooth without sculpture. Both tube and septum are semitransparent, colourless and glossy.Aperture simple, without any swelling or varix, even and not oblique. Microsculpture comprised of collabral incisions which define flat rings. These incisions, spaced by about 2–3 µm apart and rather regular in young specimens, tend to become irregular in adults.This feature causes the appearance of the shells, glossy and shining in the former, to become milky and opaque in the latter. Septum smooth, dome-shaped, with an ear-like mucro rotated toward the right by about 45°.The septum shows some more or less parallel grooves arranged like waves coming from the tip of the mucro. In terms of both curvature of the tube and shape of the aperture juveniles are quite similar to the adults, and are distinguished by the smaller diameter and the more regular microsculpture. Periostracum colourless, dull. Larval stage and operculum unknown.

Length: 1.6–1.8 mm.

Type locality: SOUTH AFRICA: Western Cape: Knysna, Gericke Point, Sedgefield.

Holotype ( Figs 8A–C View Fig , 22L View Fig , 23L View Fig ): SOUTH AFRICA: Western Cape: sh, Walker’s Point, W of Knysna , leg. J.P. Marais iii.1991 ( NMSA S3728 View Materials / T3355 ), length 1.69 mm, min. diam. (posterior end) 0.29 mm, diam. in the middle of the tube 0.33 mm, max. diam. (apertural end) 0.36 mm.

Paratypes: SOUTH AFRICA: Western Cape: 4 sh, same data as holotype ( NMSA W9660 View Materials / T3356 ); 8 sh, Knysna, Gericke Point, Sedgefield ( NMSA W9661 View Materials / T3357 ) ; KwaZulu-Natal: 1 sh, Aliwal Shoal , - 9–18 m, dived D. Herbert 21.xii.1986 ( NMSA D5269 View Materials / T3881 ); 1 sh (juv), Aliwal Shoal , off Umkomaas area , - 27 m, SCUBA, i.1988 ( JPM) .

Additional material examined: SOUTH AFRICA: Eastern Cape: 2 sh (1 broken), Mzamba, near Natal border, vii.1976 ( JPM 2119 ) ; KwaZulu-Natal: 1 sh (lost), Aliwal Shoal (off Umkomaas), - 27 m, silt from between rocks ( NMSA E1670 View Materials ) ; 1 lv, Landers Reef, off Scottburgh Area , - 45 m, SCUBA, iv.1988 ( JPM) .

Comparative material examined: C. sinuatum de Folin, 1879 , BORNEO, syntype (MNHN-IM-2000-27585); C. inhacaense Albano & Pizzini, 2011 , MOZAMBIQUE: Inhaca I., holotype ( MZB 15000 ) .

Distribution: Southern and eastern coasts of South Africa from Knysna to Aliwal Shoal ( Fig. 11 View Fig ).

Remarks: The microsculpture exhibited by C. incisum is unique among South African Caecum species. This kind of microsculpture is shown by C. sinuatum de Folin, 1867 described from Borneo. However, de Folin’s species is quite different from C. incisum , showing a very slender and slightly arched tube, a different shape of the septum and a strong constriction before the aperture. Caecum incisum occurs sympatrically with C. austrafricanum sp. n., C. intortum sp. n. and C. inhacaense , from which it can be distinguished by the even curvature of the tube, the lack of apertural swelling, the presence of incised growth lines defining flat rings throughout the tube, the lack of the macula and the different shape of the mucro.