Katian
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The Katian is the second stage of the Upper Ordovician. It is preceded by the Sandbian and succeeded by the Hirnantian Stage. The Katian began 452.8 million years ago and lasted for about 7.6 million
Paleogeography of the Katian, 450 Ma
Graptolite
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Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle C
Katian
…Shale and the Bigfork Chert, the latter containing the lower boundary of the Katian. The lower boundary is defined as the first appearance datum of the graptolite species Diplacanthograptus caudatus. This horizon is 4.0 m above the base of the Bigfork Chert…
ROM28084 Didymograptus
Diversity of graptolite colony forms
A hypothetical graptolite zooid inside its theca, reconstructed based on living pterobranchs
Pendeograptus fruticosus from the Bendigonian Australian Stage (Lower Ordovician; 477–474 mya) near Bendigo, Victoria, Australia. There are two overlapping, three-stiped rhabdosomes.