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Trepospira discoidalis
Taxonomy
Trepospira discoidalis was named by Newell (1935). It is a 3D body fossil. Its type locality is near Tyro, which is in a Missourian marine shale in the Stanton Formation of Kansas.
Synonymy list
| Year | Name and author |
|---|---|
| 1935 | Trepospira discoidalis Newell pp. 350 - 351 figs. pl. 35 f. 8-11 |
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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.
†Trepospira discoidalis Newell 1935
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| N. D. Newell 1935 | Mature examples of this species are large, commonly attaining a diameter of 40 to 45 mm. At a diameter of 45 mm. the somewhat gerontic holotype has about 61 volutions. It is seldom that the apical volutions can be counted in mature specimens and the above number is an estimate obtained with the aid of juvenile paratypes. The shell is mod-erately depressed and the apical angle is large, ranging between about 96 and 113 degrees, commonly with an angle of about 105 degrees. Next to the spiral seam there is a row of small, subhemis-pherical nodes, with acute, transverse crests. There are 25 to 40 of these in the sixth volution. The slit-band is super-marginal and is bounded outwardly by the sharp periphery and inwardly by a small but distinct lira. In large sized specimens the slit-band ranges in width between 2 and 2.5 mm. It joins the up-per surface of the whorls at a decidedly obtuse angle. The upper surface of the outer volutions is slightly convex next to the slit-band flattening inward and thence becoming gently concave over the inner two-thirds of the upper surface. The lower surface of the whorls has a low and regular convexity and the cur-vature does not increase perceptibly at the margins. The umbilicus is closed by a callus which is centrally depressed in such a manner as to resemble a spiral trough. The growth lines indicate a deeply re-entrant slit in the aperture but the depth of the slit cannot clearly be determined. Except for the growth lines and nodes referred to above the shell surface is smooth. |