Depressipoma laddi, 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

Depressipoma laddi n. sp.

( Fig. 14 D-F)

“ Liotina (Austroliotia) cf. L. botanica (Hedley) ” – Ladd 1966: 46, pl. 7, figs 9-11.

TYPE MATERIAL. — Holotype: U.S. Geological Survey , 1946-1952, Eniwetok Atoll, Marshall Islands, Elugelab Islet, sub-Recent from shallow drill hole, 11°40’N, 162°13’E, specimen slightly beach-worn at time of deposition, H 1.4, D 3.3 mm ( USNM 648301 ).

TYPE LOCALITY. — Eniwetok Atoll, Marshall Islands.

DISTRIBUTION. — Known only from holotype.

ETYMOLOGY. — Named after the late Dr. Harry S. Ladd, Department of Paleobiology, USNM, who first illustrated this species.

DESCRIPTION

Shell ( Fig. 14 D-F)

Of 2.7 whorls; profile very low for genus; whorls with weak peripheral angulation high on whorl; whorls rounded and inflated above and below angulation. Axial sculpture of 27weak,narrow ribs, weakly spinose and projecting in early whorls, but losing all spination in final whorl.Spiral sculpture of narrow ribs, forming square cancellations and pits;upper half of whorl with four weak cords, lower with three cords; emergent cord not strongly defined.Umbilical slope broad, with raised, narrow extensions of axial sculpture; umbilicus fully occluded by callus,partially obstructed by massive extension of inner lip, forming tongue that slightly projects forward but not extending near coiling axis. Final lip massive,extending for∕₄of final quarter whorl, with successively decreasing layers of deposition, with indentations conforming to spiral sculpture.Aperture slightly oblique, plane of aperture aligned with coiling axis. H 1.4, D 3.3 mm (holotype).

Operculum

Unknown. REMARKS

This species is unlike the other species of Depressipoma n. gen. and all species of Liotipoma in having axial ribs that are not strongly projecting at the periphery, in either apical or basal view, except in the early stages. The sculpture of the base is more clathrate than that of other species.

This species is unlikely to be sexually dimorphic because its low profile would not allow room for a brooding cavity in the umbilicus.

Figures

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.