↑ Obut & Rytzk, 1958. Ordovician and Silurian Dendroidea of Estonia.
Two species of the genus Callograptus Hall, 1865 (Graptolithina, Dendroidea) from the Lower Ordovician of Bohemia. Kraft J, Bulletin of Geosciences, volume 74, issue 1, pages 21–26
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