Rhombipoma rowleyana, Mclean, 2012

Mclean, James Hamilton, 2012, New species and genera of colloniids from Indo-Pacific coral reefs, with the definition of a new subfamily Liotipomatinae n. subfam. (Turbinoidea, Colloniidae), Zoosystema 34 (2), pp. 343-376 : 370-372

Rhombipoma rowleyana n. sp.

( Fig. 15 A-C)

TYPE MATERIAL. — Holotype: stn 86-250, Rowley Shoals, N end Mermaid Reef , off northern Western Australia, 17°03’S, 119°36’E, 18-20 m, 20.VIII.1986, Twila Bratcher, in shell grit sample, 1 damaged shell with first whorl eroded and with agglutinated sand filling aperture and exposed final quarter whorl, in which base of shell is missing, H 1.5, D 3.2 mm ( AMS C.212474, ex LACM).

TYPE LOCALITY. —Rowley Shoals, N end Mermaid Reef, off northern Western Australia.

DISTRIBUTION. — Known only from the holotype.

ETYMOLOGY. — After the type locality, Rowley Shoals.

DESCRIPTION

Shell ( Fig. 15 A-C)

Of about three whorls, profile very low, whorls rounded. Axial ribs 22 in basal view, plus seven more closely spaced axials of lesser strength in advance of final lip. Spiral sculpture of two broad peripheral cords arising at final stage and extending over varix of final lip; spiral sculpture lacking on upper part of whorl; spiral sculpture on base of broad, low subtending cord; last half whorl rapidly expanding in diameter. Final lip comprised of about eight closely spaced axials of similar strength to those that precede the lip; final lip filling about ⅓ of final quarter whorl; base of final lip broken in holotype, but tip of tongue intact, club-like, extending forward of aperture. H 1.5, D 3.2 mm (holotype).

Operculum

Unknown.

REMARKS

Rhombipoma rowleyana n. gen., n. sp. is comparable to L. laddi n. sp. ( Fig. 14 D-F) in its extremely low profile, and even more rounded final whorl, but differs in lacking the prominent spiral cords that produce the clathrate sculpture of that species. The full morphology of the umbilical area is not clear because the base of the shell is broken, but if this species is sexually dimorphic, it is unlikely that the holotype is a female shell because there seems not to be an umbilical cavity bordered by a raised rib. It is likely that the extreme lenticular profile precludes sexual dimorphism in this species.

Figures

FIG. 15.— A-C, Rhombipoma rowleyana n. gen, n. sp. holotype (AMS C.212474,ex LACM stn 86-250),N end of Mermaid Reef, Rowley Shoals,off northern Western Australia,18-20 m,H 1.5,D 3.2 mm (base of shell broken and filled with agglutinated sand);D-F, Paraliotipoma sirenkoi n. gen., n. sp. holotype (ZISP 61624/1), Sea Horse Shoal, South China Sea, 10-320 m, H. 2.7, D 4.2 mm. Scale bars: 1 mm.

FIG. 14. — A-C, Depressipoma kwajaleina n. gen., n. sp.holotype (LACM 3213),Kwajalein Atoll,Marshall Islands,20 m,H 1.7,D 3.2 mm; D-F, Depressipoma laddi n. gen., n. sp. holotype (USNM 648301), Elugelab Islet, Eniwetok Atoll, Marshall Islands, H 1.4, D 3.3 mm. Scale bars: 1 mm.