Morphological Evolution of Eurasian Bryozoans during Famennian–Tournaisian

Abstract

Abstract: The main trends in the morphological evolution of bryozoans at the Devonian-Carboniferous boundary were established when studying the Late Devonian–Early Mississippian bryozoans of Eurasia. The diversity of vertical colonies increased from Early Famennian to Late Tournaisian. An increase in their strength occurred by growth of the exozonal skeleton due to the growth of vesicular tissue in cystoporates, thickening of the autozooidal walls in trepostomates, complication of polymorphism in cryptostomates, and thickening of the branches in fenestrates. The most rapid evolutionary changes were observed in rhabdomesine bryozoans of the order Cryptostomata, expressed in the change of the spiral arrangement of autozooids to complex one and a high diversity of heterozooids and styles. The development of keels, nodes, superstructures, acanthostyles, and spines in bryozoans provide protection from predators.