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Goniasma gzheliensis
Taxonomy
Goniasma gzheliensis was named by Mazaev (2011). Its type specimen is PM RAS 4471/6-17, a shell, and it is a 3D body fossil. Its type locality is Locality 006. Section near the Gzhel station, Bed 8, which is in a Pavlovoposadian carbonate limestone in the Turabievo Formation of the Russian Federation.
Synonymy list
| Year | Name and author |
|---|---|
| 2011 | Goniasma gzheliensis Mazaev p. 1566 figs. pl. 1 f. 5-7 |
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
†Goniasma gzheliensis Mazaev 2011
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| A. V. Mazaev 2011 | The shell is small, turreted, turriform, composed of at least ten carinate whorls. The suture is very thin, hardly discernible. The protoconch is orthostrophic, composed of one or two rounded whorls. Juvenile whorls are composed of at least four whorls, carinate in profile, ornamented with four spiral lirae separated by equal spaces; the sutural lira is well developed, the carina marks the second main lira. The first main lira is at the middle of the upper whorl face between the sutural lira and carina. In adult whorls, the carina marks the first main lira, whereas the sutural lira gradually weakens to become obsolete on the last whorls. The upper whorl face between the suture and carina in the first adult whorl is nearly the same as the spaces between the first and second and second and third main lirae; then, it gradually widens and, in the last whorls, the ratio of the upper whorl face width to the lower whorl face width varies from 0.83 to 0.93. The whorl face above and below the carina is nearly straight or slightly concave in the profile. The lower whorl face is ornamented with four main spiral lirae; the first lira (as mentioned above) marks the carina, while the suture is developed immediately on or under the fourth lira. The spaces between the lirae are almost equal, and only in the last whorls they are paired. The spaces within both pairs of lirae are equal, and at least twothirds of the size of the spaces between the pairs. Whorl base is ornamented with one basal spiral lira. In the first adult whorls, this lira is thinner than the others, positioned considerably closer to the fourth main lirae, whereas, in the last whorls, the thickness of the lira increases and matches that of the main spiral lirae; the space between it and the fourth main spiral lirae is equal to that between any pair. The selenizone in adult whorls is located immediately under the carina and bounded by the first and second main spiral lirae, and its surface is smooth and concave. Sometimes, its surface possesses a very thin auxiliary spiral lira. The aperture is pentagonal in cross section, the columella is moderately long, arcuate at the base. The outer lip margin and slit are not preserved. Growth lines are indiscernible. |