Diagnoza

Possible M elements almost geniculate, cusp of most elements with sharp edges and bases with oval contour.

Derivation of name: Referring to some similarity of one element in the apparatus to that of the Ordovician genus Oistodus.

Porównanie

Elements of the species are characteristic in their Drepanoistodus-like appearance and are easy to separate from other associated simple-cones. It is not ecologically associated with species of Mitrellataxis with smooth elements and samples rich in the latter do not contain J. oistodiformis. Identification of discrete element types of the apparatus was possible owing to their abundance in samples Ost-12 and J-24.

Elements tentatively identified as belonging to the platform series have a strongly bent cusp. They form two classes differing in outline of the base (Fig. 121), those with rounded triangular outline are provisionally proposed to be P₁ elements, base outline of possible P₂ elements is circular. Elements with a rather erect cusp show the symmetry transition series from the strictly symmetrical probable S₀ elements through those with the base flattened from one side (S_1-2) to those having flattening on both sides (S_3-4). A separate class is represented by probable M elements with the whole cusp strongly inclined to the base and very asymmetric.

From other species of the genus, J. oistodiformis differs in the shape of possible M elements and relatively distinct classes of the element types (at least P, S, and M). Sandberg and Dreesen (1984) illustrated even more advanced, fully geniculate elements associated with equally derived other elements from the late Famennian (expansa Zone) of Colorado and England. In each of those localities they co-occur with different icriodontids. The lineage seems thus to have been evolving rather fast.

Autekologia

Występowanie geograficzne

Probably the late C. marginifera Zone at Jabłonna, Miedzianka and Łagów, certainly the P. trachytera Zone at Jabłonna, Kowala, Łagów and Ostrówka, possibly continued to the early L. styriacus Zone at Jabłonna and Ostrówka.

Zasięg czasowy

Materiały muzealne

934 specimens.

Literatura

Dzik, J. 2006. The Famennian "Golden Age" of conodonts and ammonoids in the Polish part of the Variscan sea. Palaeontologia Polonica 63, 1-359.