Diagnoza

the tubercles are arranged in longitudinal rows and ridges at the posterior part of the plafform are parallel to its margin. This is probably S. sandbergi that replaced Kowala populations of S. cf . quadruplicata without any intermediates.Populations of Siphonodella from sample Ko-38 upwards in the Kowala section are distinct from  hose below in having tubercles arranged in more or less regular longitudinal rows. The inner area of the platform remains ribbed (Fig. 19H) which makes these populations different from later Siphonodella with a smooth corresponding part of the platform, where only irregular tubercles may develop. In this respect they me similar to apparently much younger American S. obsoleta and S. isosticha.

The holotype of S. sandbergi Klapper, 1966 comes from the sample taken from the basal 6 inches of a dark shale unit at South Fork Rock Creek in Big Horn Mountains, Wyoming. Four other species of Siphonodella have been identified in this sample by Klapper (1966), namely S. cooperi, S. obsoleta, S. quadruplicata, ard S. sexplicata. This makes either homogeneity of the sample or taxonomic identifications of those species unlikely (perhaps both). The meaning of S. sandbergi thus

remains to be clarified.

According to the original description (Klapper 1966: p.19), the type series shows an extremely short free blade. Although only a few specimens in the Kowala samples have the free blade partially preserved, it does not seem very short (udging from the thickness of its broken base) and the dorsal part of the element is narrow, as in the type specimen of S. obsoleta. More completely preserved specimens are small in size and there may be an ontogenetic difference in proportions between the free blade length and size of the platform. A relatively short free blade characterises also adult specimens of S. belkai sp. n., that appears in Polish sections surprisingly low and must have been derived from an ancestor with S. sandbergl morphology. Perhaps S. sandbergi developed allopatrically to the European lineages of ridged Siphonodella, and much earlier. In Muhua,  pecimens of S. sandbergi with a short free blade occur high in the section (sample Mu-41; see also Ji et al. 1989).

The species identity of the Kowala series of those Siphonodella populations remains obscure. ff

the longitudinal ridges are homologous to those in S. sandbergi the Kowala population would

represent a morphology ancestral for S. sandbergi. Being unable to find a better affiliation for it I will

apply the name S. sandbergi until its relationships are clarified.

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.