Atlanta plana Richter, 1972b
Overview
This is a medium sized, dextrally shelled, pelagic snail, 0.4 cm in diameter with large eyes and a single swimming fin. The shell is large, strongly flattened and keeled. The faintly violet spire is small. The operculum has a spiral line of radial dents (Atlanta plana 1, Atlanta plana 3). It is a carnivore predating on relatively large zooplankton. This species occurs in the Indian Ocean.
Taxonomic Description [after Richter, 1987]
The shell is large and strongly flattened. The spire is small(Atlanta plana protoc 2). The suture is deep and clearly visible. A very faint spiral sculpture is seen on the two inner most whorls of the spire. The spire is faint violet, the keel base is darker. The last whorl is very flat. The aperture is inflated. There is no decalcification in the spire (Atlanta plana 2, Atlanta plana). The operculum (type B) is slender oval, oligogyre with a small nucleus with a spiral line of radial dentation (Atlanta plana operculum, Atlanta plana operculum1). The eyes (type A) have a cylindrical pigment mantle and a triangular dorsal window. The radula is large, narrow-triangular with large teeth; the median tooth is broad rectangular with a strong cusp and lateral wings; lateral teeth are unicuspoid with a remarkable high basal plate; additional teeth in one pair are of different size and short. There is no sexual dimorphism.
Shell diameter 4 mm.
Juveniles
The juveniles have a small, dextrally coiled shell. The Atlanta plana protoconch I is smooth, the protoconch II shows 3 clear spiral lines. The Atlanta plana veliger also has lines on the underside of the whorl and the sides of the whorls are rounded. The protoconch I is clearly elevated above the protoconch II. In Atlanta plana juv. specimens the groove of the keel is already seen on the third whorl.
Reproduction
In this species the sexes are separate.
Ecology
This species is a carnivore and epipelagic.
Distribution
This species occurs in the Indian Ocean, a map is not given as the records are not well documented, see the Atlanta plana map.
Types
Atlanta plana Richter, 1972: 90, figs. 4, 6, 8.
Holotype: SMFM 223055. Paratype: SMFM 223056.
Type locality: Indian Ocean. Coll.: CMEE.