Knightites (Retispira) triangularis, 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 : 72

Knightites (Retispira) triangularis n.sp.

PI. 2 figs 1-3

Description. Shell small, isostrophic with fan-like form, narrowly phaneromphalous; umbilicus partly obscured in lateral view by a flap-like extension from the parietal inductura. Protoconch concealed, seemingly minute planispiral. Teleoconch with whorls involute and with maximum diameter of whorl less than height of spire; ornament dominated by coarse spiral costae modified by weak transverse lirae with pustules formed at their intersection; spiral costae, about 18-20 in the last whorl, with 1 or 2 weaker spiral costae between the coarse costae; transverse lirae less prominent, but regularly spaced; side of selenizone raised, ornamented by 8 to 9 closely spaced spiral lirae and curved lunulae; shell consisting of 2 layers, the inner layer retaining the same ornamentation as the outer layer, but weaker. Aperture broad, crescentic, only slightly flared at the side; slit short; parietal inductura moderately thickened, approximately one quarter of a volution.

Types. Holotype ( F78351 ) and 1 figured paratype ( F78352 ).

Type locality. About 250 m west of Babbinboon Lane, in Swains Gully, 15 km south-west of Somerton, NSW (Locality 25).

Stratigraphic position. In bioclastic limestone 130 m above the base of the Namoi Formation.

Geographic distribution. Swains Gully.

Geological age. Middle Tournaisian.

Etymology. Referring to the triangular shape in the apertural view.

Remarks. This species resembles Knightites (Retispira) culleni Campbell & Engel and Knightites (R.) multilirata n.sp. in having reticulate shell ornamentation, but differs from the former by having a triangular shell shape and coarser ornamentation, and from the latter in having a narrow umbilicus and raised selenizone. Knightites (Retispira) triangularis n.sp. is characterised by coarse wave-like spiral costae with raised wide selenizone whereas K. (R.) multiliratahas net-like ornament with flat selenizone.