{{Short description|Species of gastropod}} {{Use dmy dates|date=November 2020}} {{Speciesbox | fossil_range = Pliocene-Recent<ref name="Janssen 2007"/> | image = Atlanta cf echinogyra.png | image_caption = Apical view of the shell of ''Atlanta'' cf. ''echinogyra'' from the Pliocene of Philippines. Notice the flange-like keel. | genus = Atlanta | species = echinogyra | authority = Richter, 1972<ref>{{in lang|de}} Richter G. (1972). "Zur Kenntnis der Gattung ''Atlanta'' (Heteropoda: Atlantidae)". ''Archiv für Molluskenkunde'' '''102''': 85–91.</ref> | synonyms_ref = | synonyms = }}

'''''Atlanta echinogyra''''' is a species of sea snail, a holoplanktonic marine gastropod mollusk in the family Atlantidae.<ref name="WoRMS">{{WRMS species|430420|''Atlanta echinogyra'' Richter, 1972|||WoRMS (2009). Atlanta echinogyra Richter, 1972. Accessed through: World Register of Marine Species at <nowiki>http://www.marinespecies.org/aphia.php?p=taxdetails&id=430420</nowiki> on 14 August 2010}}</ref>

==Description== ''Atlanta echinogyra'' was described in 1972 by Dr. Gotthard Richter (from Senckenberg Museum, Frankfurt am Main, Germany) based on specimens collected during the Meteor Expedition to the northern Indian Ocean.<ref name="Seapy 2010"/> Richter named the species after the unique structure of the opercular gyre, with its raised spiral row of spines.<ref name="Seapy 2010"/>

''Atlanta echinogyra'' is a small species (to 2.5&nbsp;mm shell diameter).<ref name="Seapy 2010"/> The shell is colorless, although the tissues underlying the shell spire give it a red-violet to red-brown color.<ref name="Seapy 2010"/> The spire is low conical and consists of 3-3.25 whorls.<ref name="Janssen 2007"/><ref name="Seapy 2010"/> The spire whorls have incised sutures and bear low spiral ridges on the second through most of the fourth whorls.<ref name="Seapy 2010"/> The outer edge of the third and fourth whorls have a raised ridge (seen best in the larval shell).<ref name="Seapy 2010"/> The fourth whorl (first teleoconch whorl) increases rapidly in width and bears a flange-like keel.<ref name="Janssen 2007"/> The keel is moderately elevated with a slightly truncate leading edge.<ref name="Seapy 2010"/> The keel does not insert between the last two shell whorls.<ref name="Seapy 2010"/> The keel base is either clear or brown.<ref name="Seapy 2010"/> The early whorls are covered with a distinct and relatively coarse ornament consisting of four spirals.<ref name="Janssen 2007"/> This ornament is also visible on the base of the shell, where it is present in the umbilicus, on the last part of the protoconch.<ref name="Janssen 2007"/>

Eyes are type a.<ref name="Seapy 2010"/> Operculum is type c, with a gyre that bears a raised spiral row of strong, distally-tapering spines (hence the specific epithet, "echinogyra").<ref name="Seapy 2010"/> Radula is type I, with unlimited numbers of tooth rows and lacking sexual dimorphism.<ref name="Seapy 2010"/>

Description overview: * Shell small, with a maximal diameter of 2.5&nbsp;mm elevated spiral row of outwardly-directed spines that taper distally<ref name="Seapy 2010"/> * Shell colorless<ref name="Seapy 2010"/> * Spire region of shell red-violet to red-brown due to underlying tissues<ref name="Seapy 2010"/> * Spire of 3-3/4 whorls, with low conical shape and deep sutures<ref name="Seapy 2010"/> * Low spiral ridges present on the second through most of the fourth spire whorls<ref name="Seapy 2010"/> * Outer edge of third and fourth whorls with a raised ridge<ref name="Seapy 2010"/> * Keel moderately elevated, with a slightly truncate leading edge<ref name="Seapy 2010"/> * Keel does not insert between last two whorls<ref name="Seapy 2010"/> * Keel base clear (North Pacific Ocean) or dark to yellow-brown (northern Indian Ocean)<ref name="Seapy 2010"/> * Eyes type a<ref name="Seapy 2010"/> * Operculum type c; gyre bears a raised spiral row of distally-tapering spines<ref name="Seapy 2010"/> * Radula type I<ref name="Seapy 2010"/>

==Distribution== Geographic distribution of ''Atlanta echinogyra'' is Indo-Pacific.<ref name="Seapy 2010"/>

In the plankton samples from the Meteor Expedition studied by Richter (1974), ''Atlanta echinogyra'' was the fourth most abundant species of heteropod (accounting for 9.1% of the total).<ref name="Seapy 2010"/> By contrast, the species was uncommon off northeastern Australia (ranking ninth, accounting for 1.5% of the total number of heteropods collected) in a study by Seapy et al. (2003).<ref name="Seapy 2010"/> In Hawaiian waters ''Atlanta echinogyra'' was variable in its presence and numbers among different collections, ranking eleventh out of thirteen species of atlantids (Seapy, 1990a); from five different sampling periods between 1984 and 1986, it was not collected twice, was represented by a single individual once, and by 27 and 19 individuals in two collections.<ref name="Seapy 2010"/> In eastern Australian waters, Newman (1990) recorded ''Atlanta echinogyra'' as rare in northern and central Great Barrier Reef waters.<ref name="Seapy 2010"/> Thus, it would appear that in the Pacific and Indian Oceans, ''Atlanta echinogyra'' is only abundant in the northern Indian Ocean.<ref name="Seapy 2010"/>

===Fossil distribution=== ''Atlanta'' cf. ''echinogyra'' is known from the Pliocene of Anda, Pangasinan, Luzon, Philippines.<ref name="Janssen 2007"/>

==Ecology== Vertical distribution limited to the upper 100 m in Hawaiian waters.<ref name="Seapy 2010"/>

==References== This article incorporates CC-BY-3.0 text from references.<ref name="Janssen 2007">{{Cite journal| author=Janssen A. W.| title=Holoplanktonic Mollusca (Gastropoda: Pterotracheoidea, Janthinoidea, Thecosomata and Gymnosomata) from the Pliocene of Pangasinan (Luzon, Philippines)| journal=Scripta Geologica| year=2007| volume=135| url=http://www.scriptageologica.nl/07/nr135/a02| access-date=19 August 2010| archive-url=https://web.archive.org/web/20110724165136/http://www.scriptageologica.nl/07/nr135/a02| archive-date=24 July 2011| url-status=dead}}</ref><ref name="Seapy 2010">Seapy R. R. (2010). ''Atlanta echinogyra'' Richter 1972. Version 28 March 2010 (under construction). http://tolweb.org/Atlanta_echinogyra/28756/2010.03.28 in The Tree of Life Web Project.</ref> {{Reflist}}

{{Commons category}} {{Taxonbar|from=Q4816188}}

Category:Atlantidae Category:Gastropods described in 1972