CLADISTIC ANALYSIS OF SOME EARLY MISSISSIPPIAN CONODONT GENERA BASED ON HISTOLOGICAL FEATURES

Computer program PAST(v.0.65) by R. Hammer and D. A. T. Harper was used for cladistic analysis of some Early Mississippian conodont genera, namely: Spathognathodus (s.l), Polygnathus, Siphonodella (primitive and advanced), and Pseudopolygnathus. Two morphological and six histological characters of the genera were used in parsimony analysis: morphological type of Pa element (bladeform or platform); size and from of basal cavity; presence of interlamellar arcs in the platform rostrum; occurrence of interlamellar septa in the free blade; depth of roots of carina core composed by paralamellar tissue and white matter; presence of plates of paralamellar tissue situated in the upper part of platform; presence of plates of paralamellar tissue situated in the lower part of platform. Spathognathodus (s.l.) is considered as outgroup. Other genera are distributed in the cladogram in the following order: Spathognathodus, Polygnathus, Pseudopolygnathus, primitive Siphonodella, and advanced Siphonodella. This order does not correspond directly to phylogenetic relations of the genera. However, close affinities of Pseudopolygnathus and Siphonodella were supposed by J. Dzik (1997), and there are no doubts that primitive and advanced Siphonodella compose phyletic lineage. Thus, cladistic analysis of both the morphological and histological features of the Mississippian conodonts is promising for reconstruction of their phylogeny.