Flotation devices in planktic graptolites

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Abstract
Four unique graptolite specimens representing Dicellograptus gurleyi, Pseudoclimacograptus angulatus, Glossograptus ciliatus, and Climacograptus tubuliferus are described. They are rhabdosomes in which compressed circular objects interpreted as floats are attached to the nemata. Several additional objects isolated from carbonates and found on shale surfaces are described and interpreted as floats that functioned in juvenile rhabdosomes but became detached later in astogeny. They could be mistakenly identified as palynomorphs. These specimens serve as additional supporting evidence for previous work in which a float attached to a juvenile rhabdosome was described and a passive buoyant mode of life for planktic graptolites was suggested.