Species Pleuroacanthites polycyclus WÄHNER
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Description

Pleuracanthites polycyclus, after the distinct nodule stage and a few bulging ribs, is almost smooth on the following coils. Only very shallow ribs or ripples can be observed on the shell. The cross-section of the coils is thicker than high in the juvenile stage (on the innermost coils); however, this ratio quickly reverses. The turns increase only slightly in width, the cross-section becomes highly oval from a dm of 2cm at the latest. The flanks are always rounded. A flattening as in Ps. naumanni or Euphyllites waehneri is not achieved.
Shown here is a very large, complete specimen in which the living chamber is almost 1.5 turns long. The mouth is obviously preserved.
WÄHNER points out the great similarity to Psiloceras, to which this species could also be placed if the inner coils were not preserved. These are typically much wider than high for Pleuracantithes.

* Description according to WÄHNER 1894 & LANGE 1952, supplemented

Compare

Pleuracanthites polycyclus is characterised by the almost complete absence of ribbing. From Ps. naumanni glabrum LANGE, Ps. calliphyllum NEUMAYR and other smooth forms, which are sculpless, Pl. polycyclus differs by the large navel width and the thus many visible convolutions. Occurrence: together with or just above Ps. naumanni.

Dimension

Dimensions with D= 70mm:
Nw % v. D: ca. 59%
Wh % v. D: ca. 22%
Wb % v. D: ca. 20%

Literature
  • 1884 Aegoceras calliphyllum Neum. mut. polycyclus n. f. – WÄHNER S. 37, Taf. 15.2-3
  • 1894 Pleuracanthites (Psiloceras) polycyclus Wähner. – WÄHNER S. 253, Taf. 57.1-4
  • 1952 Pleuracanthites polycyclus Wähner – LANGE S. 95, Taf. 11.5
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