Acutimitoceras prorsum
Sugerowana cytacja: Dzik,J. 2015. Acutimitoceras prorsum (Schmidt, 1925) . Ikonoteka (http://ikonoteka.paleo.pan.pl/xwiki/bin/viewrev/Species/Acutimitoceras+prorsum+)
 Acutimitoceras prorsum (Schmidt, 1925) from the Protognathodus kockeli horizon at Kowala in the Holy Cross Mountains. Diagnoza As mentioned above, the bedding plane of a tuffite 1.2 m above the top of the Wocklumerla limestone in the Kowala trench is covered with numerous specimens of ammonoids probably conspecific with, or at least closely related to, Rhenish Acutimitoceras prorsum. When compared with the type population from Stockum in the Rhenish Massif (Kom 1994; see also House 1992), the Kowala specimens seem to differ slightly in having a less prominent ventral sinus of the aperture and more regular distribution of growth lines. However, this may be partially a result of differences in preservation. More importantly, the Kowala assemblage seems to be monospecific as more than a hundred fragmentarily preserved specimens seem to represent the same conch morphology. The same species occurs also in the laminated limestone 1.5 m above but there it is very rare. Some other coiled mollusc conchs have been found there but these seem to be pelagic? bellerophontid monoplacophorans. Conch aperture with radially running lateral margins and gentle ventral sinus; rounded conch venter with no signs of angulation. Porównanie The species does not fit the diagnostic character of the genus in respect to the conch form but the shape of aperture resembles that in the type species and this supports its ancestral position within the lineage. All specimens from Kowala are flattened and fragmentary but some show the original geometry leaving little doubt that this is a generalized prionoceratid with an oval whorl cross section. The distinct growth lines are not so apparent in the German material but this may be due to exfoliation of the conch surface. Autekologia Występowanie geograficzne Kowala. Zasięg czasowy P. kockeli horizon. Materiały muzealne ZPAL: Numerous crushed and fragmentary specimens covering slabs of tuffite. Literatura Dzik, J. 1997. Emergence and succession of Carboniferous conodont and ammonoid communities in the Polish part of the Variscan sea. Acta Palaeontologica Polonica 42, 57-170. Dzik, J. 2006. The Famennian "Golden Age" of conodonts and ammonoids in the Polish part of the Variscan sea. Palaeontologia Polonica 63, 1-359. |
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