DETERMINATION OF UPPER TRIASSIC AND LOWER JURASSIC ICHTHYOLARIAS USING MORPHOGENETIC PROGRAMS

Species of the genus Ichthyolaria from the Upper Triassic and Lower Ju rassic are investigated and described. First the morphology of each ch amber, rib and the keel surrounding the test are transferred to geomet rical functions reducing complete test morphology to a small set of pa rameters. Then dependencies of each parameter on growth are modelled b y geometrical functions representing the morphogenetic programs. Param eters of these growth independent functions are used as characters in classification analyses based on clustering and ordination methods. Gr oups demonstrating homogeneity in characters can now be interpreted as biological species using the criterion of cohesion in morphogenetic p rograms. Classification of Ichthyolarias results in 10 species, where one of lowermost Jurassic age (Ichthyolaria gigantea) and two of Trias sic age (I. serotriadica, I. parvolimbata) are new. Evolutionary tende ncies and phylogenetic relationships are proven using multivariate dis criminant analyses.