Morphology of the early ontogenetic stages of advanced Siphonodellids (conodnta, early carboniferous)

Possibility of taxonomic diagnostics of the juvenile Pa-elements of the advanced Siphonodella is considered. The set of the observable taxonomic features varies significantly in dependence of the ontogeny stage. The adult Pa-elements demonstrate full association of morphological features, but the juvenile forms can be distinguished just on the basis of carina curvature, platform outline and ornamentation, the rostrum morphology, and the element symmetry. Some species share these features and are indistinguishable at the early stages of ontogeny. Siphonodella crenulata, S. duplicata, S. quasinuda, S. semichatovae M2, S. lobata are recognizable at the earliest ontogenetic stage. The group having numerous long ridges can be differentiated at the species level just since the second stage of ontogeny (elements composed by more than 4 lamella sets). Siphonodells with more than two short ridges and S. hassi can be determined since the second stage ontogeny too.