Učënye Zapiski Kazanskogo Universiteta. Seriâ Estestvennye Nauki (Sep 2022)

Evolutionary morphogenesis of the Late Paleozoic bryozoans from the genus Shulgapora Termier & Termier, 1971

  • Z.A. Tolokonnikova,
  • A.A. Ischenko

DOI
https://doi.org/10.26907/2542-064X.2022.3.501-513
Journal volume & issue
Vol. 164, no. 3
pp. 501 – 513

Abstract

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Bryozoans of the genus Shulgapora Termier & Termier, 1971 (Fenestrata) are known form the Middle Carboniferous–Middle Permian of Eurasia, Australia, and North America. Here, we explored their phylogenetic variability related to the development of cyclozooids using the materials from the collections of the Borissiak Paleontological Institute of the Russian Academy of Sciences and from the Stuckenberg Geological Museum of Kazan Federal University. The oriented sections of the fragments of bryozoan colo­nies were examined by light microscopy, the relevant published data were also considered. The functions of cyclozooids seen in the fossils studied were defined. The species composition of the genus was revised and specified. The type species and taxa abundant within the Russian Platform of the Ural Mountains were redescribed. The taxa originally assigned to the genus Shulgapora were revealed. Their main evolutionary trends were traced. A total of 11 morphological characters were analyzed based on 18 species belonging to the genus Shulgapora, and 6 of them demonstrated variability over time. The evolutionary morphogenesis of the genus was outlined. It was suggested that the genus Shulgapora probably descended from the genus Ignotifenestella Morozova, 1974. This evolution was accompanied by an increase in the number of rows of autozooids on branches, the width and length of fenestrules, the number of cyclozooids, as well as by a change in the shape of the middle section of the autozooid and by the loss of the lower hemiseptum. Parallels were drawn between the functions of cyclozooids observed in the fossil bryozoans with avicularia in modern representatives of the group. Our findings are important for a better understanding of the evolution of the entire phylum Bryozoa and the environmentally driven changes in the development of benthic invertebrates.

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