Caecum temporale, Walter & Renda, 2024

Walter, Angelo Vannozzi & Renda, Walter, 2024, Sampling the depth: New data on the Caecidae (Mollusca, Gastropoda) from northeastern Papua New Guinea, Zoosystema 46 (14), pp. 327-347 : 342

Caecum temporale n. sp.

( Fig. 7 A-C)

urn:lsid:zoobank.org:act:AE3D8F94-B452-4EFC-8CE7-6F3D1FEA47D3

Caecum cf. campanulatum Raines & Pizzini, 2005 . — Pizzini et al. 2013: 21, fig. 11B.

TYPE MATERIAL. — Holotype. Fiji • lv (length 1.26 mm, Fig. 7A, B ); S Viti Levu , MUSORSTOM 10 Stn DW1381; 18°18’S, 177°54’E; 275-430 m depth; 18.VIII.1998; MNHN-IM-2012-37957 .

TYPE LOCALITY. — Pacific Ocean, Fiji, S Viti Levu, 18°18’S, 177°54’E, 275-430 m depth.

OTHER MATERIAL EXAMINED. — Papua New Guinea • 1 sh; New Ireland; KAVIENG 2014 Stn DW4464; 2°43’S, 150°36’E; 140- 214 m depth; 3.IX.2014; MNHN-IM-2000-38950 .

DISTRIBUTION. — Known from northeastern PNG and Fiji ( Pizzini et al. 2013).

ETYMOLOGY. — From Latin temporalis (temporary) due to the presence of obvious remains of the temporary septum in all examined specimens.

DESCRIPTION

Shell small for the genus, colourless, semitransparent. Protoconch unknown.Teleoconch tubular, arched, almost smooth. Early teleoconch unknown.Adult shell subcylindrical, smooth, tapering toward the apex. Sculpture of distinct but not prominent irregular rings throughout the tube. Microsculpture of only irregular growth lines. Aperture preceded by a minute but clear swelling, ending with a reflected lip. Septum dome-shaped without mucro, on the cutting plane. Remains of the temporary septum visible. Operculum circular, thin, flat. Soft parts unknown. Holotype: length 1.27 mm, max diam 0.27 mm, min diam 0.20 mm.

REMARKS

This very small elusive species is known from a couple of specimens only but could not be classified according to any known species. It was known from a single specimen, tentatively classified as C. campanulatum Raines & Pizzini, 2005 , endemic to Easter Island ( Pizzini et al. 2013). The finding of a further specimen from PNG convinced us about the identity of this species. However, the specimen from Fiji, already in the MNHN collection, was preferred as holotype due to the better condition.

Caecum temporale n. sp. is distinctive due to the persistence of the temporary septum, which disguises its actual shape and makes the septum show an irregular appearance.

The new species can be compared with Caecum succineum and C. bathus Pizzini, Raines & Vannozzi, 2013 , both of them showing a substantially smooth tube and a simple, low dome-shaped septum. The former differs due to the presence of few coarse rings preceding the aperture and the regular annular microsculpture ( Pizzini et al. 2013: fig. 12C). The latter has a similar general aspect but shows a longitudinal worm-like microsculpture.

Caecum temporale n. sp. can also be compared with C. lozoueti n. sp. due to the general aspect and the simple dome-shaped septum without mucro. However, C. temporale n. sp. shows a slight but well-defined swelling before the aperture and lacks both the longitudinal striation and the worm-like microsculpture observed in C. lozoueti n. sp.

Figures

FIG. 7. — Caecum Fleming, 1813 new species: A-C, Caecum temporale n. sp.: A, B, holotype MNHN-IM-2012-37957; C, specimen from Stn DW4464 MNHN- IM-2000-38950; D-I, Caecum lozoueti n. sp.: D, E, specimen from Stn CP3957 MNHN-IM-2022-2398; F-I, holotype MNHN-IM-2012-37972. Scale bars: A, B, D-G, 1 mm; C, 0.5 mm, details not to scale. Image courtesy of D. Geiger (A), M. Hennion (B, G) and A. Le Goff (F, H, I).