Hohenegger, J. (1993). Determination of Upper Triassic and Lower Jurassic Ichthyolarias Using Morphogenetic Programs. Micropaleontology. 39(3): 233-262.

334954

10.2307/1485899 [view]

Hohenegger, J.

1993

39(3): 233-262

Publication

Available for editors   [request]

Species of the genus Ichthyolaria from the Upper Triassic and Lower Jurassic are investigated and described. First the morphology of each chamber, rib and the keel surrounding the test are transferred to geometrical functions reducing complete test morphology to a small set of parameters. Then dependencies of each parameter on growth are modelled by geometrical functions representing the morphogenetic programs. Parameters of these growth independent functions are used as characters in classification analyses based on clustering and ordination methods. Groups demonstrating homogeneity in characters can now be interpreted as biological species using the criterion of cohesion in morphogenetic programs. Classification of Ichthyolarias results in 10 species, where one of lowermost Jurassic age (Ichthyolaria gigantea) and two of Triassic age (I. serotriadica, I. parvolimbata) are new. Evolutionary tendencies and phylogenetic relationships are proven using multivariate discriminant analyses.

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