Atlanta brunnea

Atlanta brunnea is a small species (shell diameter to 2.0 mm) that is darkly pigmented (brown to reddish-and golden-brown).[5] The keel is tall and colorless, and inserts between the last and penultimate shell whorls in animals larger than 1.5 mm.[5] The spire is tall and conical, consisting of 4 whorls and possessing a complex pattern of spiral sculpture that ends on the protoconch and is replaced by spiral rows of small punctae on the teleoconch.[5] Coloration ranges from brown to amber and reddish brown.[5]

lateral view of the protoconch of Atlanta brunnea

Juveniles of this species are easily recognised by their shape and ornament.[1] The protoconch is rather high conical and has 3½ - 3¾ whorls, slowly increasing in diameter.[1] On the first whorl, in front of the nucleus, an ornament is seen of some nine or ten irregular spirals.[1] Two stronger spirals from the second whorl on delimit a subsutural zone and the base of the shell.[1] On these spirals the whorl profile is slightly angular.[1] The whole surface of the protoconch is furthermore covered with numerous finer spirals in an irregular zigzag shape, also on the base and within the umbilicus.[1] The boundary with the teleoconch is made distinct by the sudden disappearance of these spirals.[1] From that point on the whorl diameter increases rapidly, by which the shape of the shell becomes lenticular.[1] Somewhat more than one teleoconch whorl is present in the largest specimens.[1] The periphery of the body whorl is angular and bears a distinct flange-like keel.[1] The protoconch is visible in an apertural view.[1]

Eyes aretype a, operculum is type a, and radula type I.[5]

Description overview:

• The maximum recorded shell length is 1.7 mm.[6] / Maximal shell diameter is 2.0 mm.[5]
• Keel tall and colorless, and inserts between last and penultimate whorls in shells > 1.5 mm diameter[5]
• Spire tall and conical, with ornate, complex sculpture[5]
• Coloration brown to amber and reddish-brown[5]
• Eyes type a; operculum type a; radula type I[5]

Atlanta brunnea has an almost worldwide tropical and subtropical distribution pattern.[1]

It is limited to the upper 100 m of the water column in Hawaiian waters.[5] Comparison of day and night vertical distribution of abundances suggested that a portion of the population from 50–100 m migrated into the upper 50 m at night.[5]

This article incorporates CC-BY-3.0 text from references.[1][5]