A new fern from Middle Devonian of Kazakhstan |
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| Abstract: | Karagandella kabanovii gen. et sp. nov. is described. It occurs, along with Pseudosporochnus nodosus and Lepidodendropsis kazachstanica, in sediments underlain by strata containing Stropheodonta sp., Schellwienella umbraculum, Atrypa sp.,Uncinulus grandis, and Mucrospirifer cf. mesacostalis. The overlying strata contain Stropheodonta sp., Schellwienella umbraculum, Longispina mucronata, Gypidula sp., Uncinulusdis, Elythyna sp., Spinocyrtia audacula, and Mucrospirifer cf.. mesacostalis. The occurrence is assigned to the lower part of the Akbastau suite, Givetian Stage, Middle Devonian, on the basis of the invertebrate fossils. Karagandella is questionably classed with the Protopteridiales or possibly with the Zygopteridales. It is a dorsiventrally flattened branching system in which the main rachis is straight, smooth, probably terete in cross-section, and monopodially branched. Secondary branches arise alternately or oppositely and almost at right-angles to the rachis. Ultimate segments are dichotomously branched and in some instances show circinnate vernation. Anatomy and reproductive structure are unknown. The plant is compared with Protocephalopteris and Rhacophyton on the basis of the similarity in branching and is differentiated from those genera by the absence of catadromic, sporangium-bearing, branching systems, pinnules (as in Rhacophyton), and its primitive appearance. The author suggests that Karagandella can be regarded as the prototype of the large fern frond. --F. M. Hueber. |
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