PTYGMATIDINAE Pchelintsev, 1960

Kollmann, Heinz A., 2014, The extinct Nerineoidea and Acteonelloidea (Heterobranchia, Gastropoda): a palaeobiological approach, Geodiversitas 36 (3), pp. 349-383 : 356

publication ID	https://doi.org/ 10.5252/g2014n3a2
DOI	https://doi.org/10.5281/zenodo.4822752
persistent identifier	https://treatment.plazi.org/id/6A7F87DF-FF80-FF8A-E5B5-FCF455FCFE2D
treatment provided by	Felipe
scientific name	PTYGMATIDINAE Pchelintsev, 1960
status

Treatment

Subfamily PTYGMATIDINAE Pchelintsev, 1960 ( Fig. 3A, B, I View FIG )

Ptygmatidinae Pchelintsev, 1960: 51 .

Bactroptyxisidae Pchelintsev, 1965: 96 .

TYPE GENUS. — Ptygmatis Sharpe, 1850 ( 1850: 104) .

TYPE SPECIES. — Pt. bruntruntana Thurmann, 1832 ( 1832: 17) .

SUBFAMILY CHARACTERS . — Broad umbilicate to anomphalous. Whorls flat to moderately concave, rhombic in cross section.Two columellar plaits extending to detached columellar inductura. Parietal and palatal plait thin in the last whorl. External end of plaits inflated, truncated or bifurcate in earlier whorls, incisions between columellar plaits deep and bent.

REMARKS

The internal plaits are delicate in the final whorl but may become increasingly complex by the deposition of additional shell material in earlier whorls ( Fig. 3F, I View FIG ). According to Wieczorek (1998) all transitions are visible, even on the species level. Hudlestone (1889) records Ptygmatidinae taxa from the Inferior Oolite (Middle Jurassic) ranging in outline between slender and moderately broad. The increase of the apical angle accompanies a broadening of the columella cavity. The transitions are fluent and there is no reason to distinguish the Bactroptyxisidae Pchelintsev, 1965 upon species with solid columellas.