Species Metamorphites marmorei KMENT
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Description

The winding cross-section of juvenile forms is highly oval, with evenly rounded flanks, steep to overhanging umbilical wall and a narrowly rounded umbilical margin.
The inner two thirds of the flank are ribbed up to a diameter of about 23 mm. This ribbing then disappears and in its place the inner third of the flank is
a distinct spiral furrow is formed. This makes the narrowly rounded umbilical margin stand out morphologically and gives M. marmorei its characteristic appearance.
While the greatest width of the coiling in juvenile stages is approximately at the middle of the flank, it is closer to the navel in specimens with a spiral furrow. After that, the width of the coil decreases evenly - the external side consists of a relatively narrow curve.
The inner coils have weak, proradiate ribs on the inner two-thirds up to a diameter of about 23 mm. They start strongly inclined forward near the umbilical margin, but then bend backwards, reach their greatest height and extinguish. The outer third remains smooth. On the innermost coils (dm = approx. 6 mm) the proradiate ribs or ridges take up the whole flank.
The adult stages rarely show shell features apart from the spiral furrow. Very weak sigmoidal ribs or accretion stripes may be present.

Compare

Larger specimens are very easy to identify by the spiral furrow. Smaller ones show a typical Discamphiceras sculpture and can be easily distinguished from other Discamphicerates by the small navel width.
The strongly branched lobe line makes Phylloceras relatives out of the question.

Dimension

Dimensions for D= 40mm (according to Kment):
Nw % v. D: ca. 15%
Wh % v. D: ca. 52%
Wb % v. D: ca. 26%

Abmessungen bei D= 140mm (nach Kment):
Nw % v. D: ca. 12%
Wh % v. D: ca. 52%
Wb % v. D: ca. 21%

Literature
  • 2000 Metamorphites marmorei gen.n. et sp. n. – Kment S. 200, Taf. 3.6
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