Abstract

The most widely recognized classification of the class Stenolaemata requires that all post-Triassic members belong to the order Cyclostomata and that all were derived from simple Permo-Triassic stomatoporid cyclostomes. This results from pre-Triassic and post-Triassic classifications, independently developed, using different characters and juxtaposed at the Triassic-Jurassic boundary with no consideration of possible phylogenetic connections. Preliminary evidence based on using the same taxonomic characteristics suggests that post-Triassic stenolaemates were also derived from the Paleozoic orders Trepostomata, Cystoporata, and possibly the Cryptostomata, making the present concept of the order Cyclostomata polyphyletic.--Modified journal abstract.

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