Straparollus brevis, 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 : 73-74

Straparollus brevis n.sp.

PI. 3 figs 6-8

Description. Shell very small, low-spired trochiform, widely phaneromphous. Protoconch of 5 or 6 smooth whorls with a sharp demarcation between the protoconch and teleoconch. Teleoconch of 2Yz smooth and rounded whorls; whorl profile well arched between sutures; with broadly rounded revolving shoulder on its upper surface and slight flattening above; suture moderately deep; ornamentation of fine growth lines; base and umbilical surface strongly rounded. Aperture almost circular; parietal inductura thin; columellar lip thin, arcuate; outer lip with shallow sinus close to the upper suture, swinging forward below sinus and then rounding backward to cross the lower face and the base with a slight backward obliquity, becoming vertical on the umbilical face.

Types. Holotype ( F78363 ) and 2 figured paratypes ( F78364 ). There are 20 unfigured additional specimens ( F78365 ) from the type locality.

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

Stratigraphic position. From 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 word brevis meaning short; referring to the low spire of the shell.

Remarks. This is smaller in size than any other species referred to subgenus Straparollus . This species has a larger pleural angle (145-150°) than in S. davidi Dun & Benson (120-130°) and the type species Straparollus dionysii Montfort (pleural angle about 80°) from Belgium. Another European species Straparollus levigatus (Leveille) and Straparollus planorbiformis de Koninck are rather flatly coiled.