| Species | Psiloceras tenerum NEUMAYR |
| Author | NEUMAYR |
| Group | Psiloceraten |
| Horizon | costosum-horizon |
| Zone | calliphyllum-zone |
| Stage | Lower Hettangian |
Description
The smooth, first turn is followed by a strong nodule stage that lasts for about one handle. This is followed by first weak, then increasingly strong ribs, which are slightly retroradiate and have the greatest height on the middle of the flank (the indicated coil thickness is measured between the ribs). The ribs become rapidly weaker near the external side and bend strongly forward. The external side is predominantly smooth. Rarely are the ribs observed translating externally.
The turn cross-section is uniformly oval, only on the last turn does the external side appear particularly tightly rounded, almost keel-like. On complete specimens, a trumpet-like mouth seam is preserved on the stone core, the shell is thickened at the point, so that nothing is noticeable with shell.
On the last turn there are quite consistently 22 ribs.
* Description according to Lange (1952), supplemented
Compare
The formation of the trumpet-like mouth must be viewed critically and is by no means a species-typical feature. Rather, it must be assumed that Psiloceras tenerum is a microcone (cf. description of the microcone of Ps. calliphyllum and Ps. strongolum in Hillebrandt & Kment, 2015). A revision is urgently needed because certainly some microconchs of other species (e.g. Ps. strongolum) have been described as Ps. tenerum. Lange (1952), for example, introduced a separate subgenus "Teneroceras" with 4 different species, but all of them are probably only variants or microconchs of other species. For the sake of simplicity, this topic will not be discussed further here.
Characteristic for Ps. tenerum are the small size and the pre-bent ribs, if the specimens come from the right finding horizon:
Psiloceras tenerum occurs together with Psiloceras costosum above the calliphyllum and below the naumanni/ johnstoni horizon.
Dimension
Dimensions with D= 26mm
Nw % v. D: ca. 44%
Wh % v. D: ca. 31%
Wb % v. D: ca. 18%
Literature
- 1879 Aegoceras tenerum – Neumayr, S. 31, Taf. 3, 4, 5
- 1886 Aegoceras tenerum Neum.– Wähner, S. 144, S. 196
- 1952 Psiloceras (Teneroceras) tenerum NEUMAYR – Lange, S. 98, Taf. 12.1-5
