Parashiela obesula, Amati & Giulio & Oliverio, 2023

Amati, Bruno, Giulio, Andrea Di & Oliverio, Marco, 2023, Shallow-water Rissoidae of the genera Alvania Risso 1826 Haurakia Iredale 1915 Parashiela Laseron 1956 Simulamerelina Ponder 1985 and Subestea Cotton 1944 Gastropoda Caenogastropoda Rissooidea from French Polynesia with the description of a new deep-water genus, Zoosystema 45 (25), pp. 803-892 : 845-846

publication ID

https://doi.org/ 10.5252/zoosystema2023v45a25

publication LSID

lsid:zoobank.org:pub:054D312B-C54B-459D-8A47-AC9CB681D7D4

DOI

https://doi.org/10.5281/zenodo.10455623

persistent identifier

https://treatment.plazi.org/id/8E9BA374-355A-4140-AA62-97657B1A62F5

taxon LSID

lsid:zoobank.org:act:8E9BA374-355A-4140-AA62-97657B1A62F5

treatment provided by

Plazi

scientific name

Parashiela obesula
status

sp. nov.

Parashiela obesula n. sp.

( Figs 29 View FIG ; 51C View FIG ; 53K View FIG ; Tables 4 View TABLE ; 5; 6)

urn:lsid:zoobank.org:act:8E9BA374-355A-4140-AA62-97657B1A62F5

TYPE MATERIAL. — Holotype. Australes • dd (height 1.32 mm, width 0.88 mm, Figs 29 View FIG ; 53K View FIG ); S of Rurutu , BENTHAUS Stn DW2010; 22°31’58”S, 151°20’59”W; 520-950 m; 24.XI.2002; MNHN-IM-2000-38714 . GoogleMaps

Paratypes. Australes • 2 dd; same locality data as holotype; MNHN- IM-2000-38715 . GoogleMaps

TYPE LOCALITY. — Australes: S of Rurutu; BENTHAUS Stn DW2010; 22°31’58”S, 151°20’59”W; 520- 950 m.

DISTRIBUTION AND SYMPATRY. — The species is at present known in the South Pacific Ocean from the Australes (Rurutu) ( Fig. 51C View FIG ), where it is sympatric with P. ambulata Laseron, 1956 and P. expansilabrum n. sp. ( Table 5 View TABLE ).

ETYMOLOGY. — From the Latin obesus, -a, -um meaning plump or fat, referring to the plump outline (- ula is a diminutive suffix).

DIAGNOSIS. — Parashiela small for the genus, height 1.07-1.32 mm. Protoconch multispiral. Teleoconch with numerous, thin axial ribs, entering the umbilical fissure; convex whorls with no angles, macro spiral sculpture of only a thin suprasutural cordlets on the first whorl, vanishing on the second whorl. Microsculpture of dense spiral threads, some more marked. Peristome duplicated, with moderately thickened varix crossed by evident growth striae.

DESCRIPTION OF HOLOTYPE

Shell ( Figs 29 View FIG A-D; 53K)

Small for the genus, height 1.32 mm, width 0.88 mm, height/ width ratio 1.50, rather robust, ovate-conical.

Protoconch ( Fig. 29E, F View FIG )

Multispiral,dome-shaped, of1.35 whorls, height 0.200mm, nucleus diameter 0.063 mm, first half whorl diameter 0.137 mm, maximum diameter 0.250 mm; protoconch I devoid of sculpture, protoconch II with only a thin spiral cordlet on lower third and microtubercles on the abapical area ( Fig. 29F View FIG ). Protoconch I-II boundary weak, sinuous. Protoconch-teleoconch boundary marked, with a sinusigera notch.

Teleoconch

Of 3.15 convex whorls, with a weak cordlet on the first whorl, fading and eventually disappearing on the second whorl. Axial sculpture on the last whorl of 37 thin, flexuose, slightly prosocline ribs, reaching the base and entering the umbilical fissure. Interspaces twice as wide as axial ribs, sculptured by numerous spiral threads, some thicker and more marked ( Fig. 29G View FIG ). Very narrow umbilical fissure. Aperture ovate-piriform height 0.58 mm, height/aperture height ratio 2.28; peristome continuous, duplicated; outer lip prosocline, slightly sinuous, smooth internally, externally expanded and very thickened, with numerous growth striae; columellar lip slightly angled medially.

Colour

Whitish colouration.

Operculum and soft parts

Unknown.

VARIABILITY

Only three specimens examined, all adults: no significant variation detected (see Table 5 View TABLE and Appendix 11).

REMARKS

See under P. rimatara n. sp. and P. rotundata n. sp. for detailed comparisons.

Kingdom

Animalia

Phylum

Mollusca

Class

Gastropoda

SubClass

Caenogastropoda

Order

Littorinimorpha

SuperFamily

Rissooidea

Family

Rissoidae

Genus

Parashiela

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