Diagnoza

Diagnosis.- The dorsal( 'posterior') part of the platform of sp elements completely smooth and convex, covered only with cell pits. The parallel arranged ridges end at the level of the cusp, the furrow between the blade and the posterior ridge continues to the tip of the platform. Free blade short

Description. - The only identified part of the apparatus are sp elements. They are very unusual, as for Siphonodella, in having smooth (except for fine reticulation produced by epithelial cells) and gently convex, anterodorsal flield of the platform. In juvenile specimens the first two ridges, that run strictly parallel to the carina, terminate abruptly at the level of the cusp and only immediately after the development of the ridges they merge with the platform margin. When additional ridges develop they tend to merge at their ends into pairs. Up to six ridges have been observed.

Porównanie

Relationships. - In a rather sudden narrowing of the platform at its ventoal end, the elements resemble those of the type series of S.sandbergi, which may suggest common origin of these two species or even derivation of  S. belkai from American S. sandbergi, but in Polish sections no S. sandbergihas been found below the range of S. belkni. Moreover a population possibly corresponding morphologically to early S. sandbergi replaces S . belkni in the Kowala section.

Remark on the type series. - This is one of the most characteristic species of Siphonodella and its discrimination is extremely easy on the basis of larges p elements. Although several complete sp elements of this species are available from the condensed section of Dzikowiec, they are invariably juvenile. There is a possibility that in the suggested course of evolution from S. sandbergi to S. belkai different ontogenetic stages behaved in different way and more than one species may have developed similar juvenile stages. The specimens from Kowala come mostly from unconsolidated clays and, despite very good preservation, are usually fragmented as a result of rock compaction. It is of more importance to have the type population clearly recognisable than to select one nicely looking specimen from it. As there is little chance to collect a complete specimen form Kowala samples in predictable future I decide to make an incomplete specimen (but showing all the diagnostic features of the species )the holotype.

Autekologia

Występowanie geograficzne

Kowala in the Holy Cross Mountains, Dzikowiec in the Sudetes,
Rzeczenice 1 borehole in West Pomerania.

Zasięg czasowy

Above S. duplicata, below
or partially together with S. carinthiaca.

Materiały muzealne

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.