Leptozyga costata, Yoo, 1994

Yoo, E. K., 1994, Early Carboniferous Gastropoda from the Tamworth Belt, New South Wales, Australia, Records of the Australian Museum 46 (1), pp. 63-120 : 85

Leptozyga costata n.sp.

PI. 16 figs 8-9

Description. Shell minute, high spired, cyrtoconoid with 7 whorls, anomphalous. Protoconch of 3 whorls, the first 11,4 whorls are smooth, and the remaining one and three quarter whorls have deeply sinuated strong collabral costae; the transition from protoconch to teleoconch abrupt, although transition within the protoconch gradual. Teleoconch of 4 whorls, whorl profile gently arched, suture moderately deep, first whorl of teleoconch ornamented by growth line only, remainder bearing collabral costae. Aperture subcircular in shape, columellar lip thin, nearly straight somewhat reflexed; parietal inductura lacking; outer lip thin, nearly straight, orthoc1ine; base somewhat extended.

Dimensions. Holotype ( F78481 ): H 1.6 mm, W 0.4 mm, PA28 °, NW 9 .

Types. Holotype ( F78481 ).

Type locality. Behind 'Kyndalyn' homestead, 10 km south-west of Somerton, NSW (Locality 24).

Stratigraphic position. In base of oolitic limestone in the Kyndalyn Mudstone Member of the Merlewood Formation.

Geographic distribution. Type locality only.

Geological age. Middle or late Visean.

Etymology. Derived from the Latin costatus meaning a rib; referring to collabral ribs on shell.

Remarks. This is an extremely rare species. Although a single specimen is available, the excellent preservation of the specimen warrants the naming of the specimen. Leptozyga costata n.sp. resembles Palaeozygopleura obesa n.sp. and Hemizyga decussata Yoo in being a cyrtoconoid with collabral cords, but differs in being minute and in having deep sinuous ornament on the protoconch.