Diagnoza

The populations of Siphonodella represented in samples Dz-44 and Dz-45 from the southern end of the Dzikowiec quarry and samples Dz-22 arrd Dz-50 (the last from a loose block) seem to not differ significantly. In all of them the sp elements are highly variable, but almost all mature specimens show characteristic features that make this form different from the populations above and below in the section. This refers to the second posterior roshal ridge which runs parallel to the margin (unlike the first one that is directed almost transversely to the platform margin), usually forming only a ramp in the dorsal part of the element. Some odd elements in the largest sarnple Dz-44 show either reversed relations between posterior ridges (the inner one being parallel to the platform margin), or do not develop the second crest despite attaining appropriate size. Those latter may, in fact, represent an exheme member of associated ,S. carinhhiaca, closely similar elements of which occur below in the section (as well as in the Carnic Alps type population; see Schtinlaub 1969).

Virtually all the Dzikowiec specimens of the species discussed show a smooth and wide central concave area of the platform. This makes them similar to rare specimens occurring in sample Ko-28 in Kowala (Fig. 19K) which may be conspecific.

Some associated ramiform elements similar to those attributed provisionally to other Siphonodela species have also been encountered (Table 1). Their apparatus attribution remains highly tentative. The gracile hi elements co-occurring in samples with Siphonodela sp elements vary mostly in the length of their processes and the angularity of the external process. In most of them the external process is relatively long and only slightly reclined; relatively robust examples probably represent species of Pandorinellina; smaller ones may as well belong to Neopolygnathus. There is no easily discernible morphologic gap in their variability. The more gracile morphs with reclined extremal process seem to represent two morphologic classes, also with a clear overlap in variability. Some of them have the extremal process bent almost strictly in the same plane as the short internal (dorsal) process, others show the extremal process curved both externally and posteriorly and a relatively  long dorsal process. I am not able to exclude the possibility that this difference refers to different locations in the apparatus (hi and ke) but the concurrence of small pl, lo, and tr elements showing unusually short processes with the short morph of hi elements is suggestive of their being members of the same apparatus, most probably of Siphonodella, sp elements of which are there of high frequency (for instance in sample Dz-15).

In the American succession sp elements without transverse ribs, characteristic for S. cooperi hassi Thompson & Fellows, 1970 (representing S. isosticha according to Klapper I97I, 1973), succeed those with prominent ribbing, classified as typical subspecieso f ,L coopei by Thompson & Fellows (1970). The same was most probably the succession of morphologies in Poland as the populations with ribbed platform (identified here as S. cf. quadruplicata) precede in time the species with a smooth cenke to the platform. The real meaning of this parallelism, which is of high importance for the time correlation between Europe and America, remains unclear. At present the proposed provisional taxonomic identifications seem to be the most parsimonious solution.

The holotype of Siphonodella isosticha Cooper, 1939 from the 'pre-Welden' shale of the Arbuckle Mountains in Oklahoma (younger than Siphonodella obsoleta according to Over 1992: p.297) is a juvenile specimen.

Porównanie

Autekologia

Występowanie geograficzne

Zasięg czasowy

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.