Atlanta oligogyra Tesch, 1906a
Overview
This is a large dextrally shelled, pelagic snail, 0.3 cm in diameter with large eyes and a single swimming fin. There are 3.5 whorls. The shell is strongly flattened and has a keel and a pink hue. The spire is small and smooth. The spire of the operculum is relatively small. It is a carnivore predating on relatively large zooplankton. This species occurs in the warm water of the Indian Ocean (Atlanta oligogyra).
Taxonomic Description [after Richter, 1986]
Shell small, with a slight pink hue, the keel base and the aperture rim are somewhat darker. Up to 3.5 whorls. The shell surface is smooth but smooth radial waves can be present at the body whorl. The spire is lower than in Atlanta lesueuri. The suture is shallow. The keel is high and less steep towards the aperture than in Atlanta lesueuri, it penetrates 1/3 whorl distance in between the whorls. Umbilicus narrow. The eyes (type A) are average sized, the transverse slit without pigment (as found in Atlanta lesueuri) is not formed. The operculum (type B) is transparent. The radula is long (up to 1340 µm) and robust but relatively small with more than 110 transverse rows, the increase in width is 18%. There is no sexual dimorphism in the radula. The median tooth is narrower than in Atlanta lesueuri.
Shell diameter 2.8 mm.
Juveniles
The juveniles have a small, dextrally coiled shell. A special description is not available.
Reproduction
In this species the sexes are separate.
Ecology
This species is a carnivore and epipelagic.
Distribution
This species occurs in the Indian and Pacific Oceans, see the Atlanta oligogyra map.
Types
Atlanta oligogyra Tesch, 1906: 54, pl. 8, figs. 14-18.
Lectotype: ZMAN (alcohol collection), Paralectotypes: ZMAN 56 specimens (alcohol collection).
Type locality: Indonesian Sea, Coll. Siboga stat 37, 66, 96, 106, 136, 138, 144, 165, 169, 172, 203, 205, 224, 225, 282.