Phylum: Hemichordata
Class: Graptolithina
Order: Graptoloidea
Family: Diplograptidae
Genus: Geniculograptus Mitchell, 1987
Cincinnatian Species: Geniculograptus typicalis

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Taxonomic History:

  • Geniculograptus typicalis includes several subspecies in the Cincinnati region.  These graptolites were previously referred to Climactograptus Hall, 1967.

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Geologic Range
Early Ordovician- Early Silurian

Common Paleoecology
Geniculograptus is an extinct genus of passively mobile planktic suspension feeders.

Identification in Hand Sample:

  • Geniculation of thecae
  • Thecae attached parallel to the axis
  • Simple stipes, subparallel margins
  • Filiform axis
  • Apertures excavated in the margin of the stipe

Geographic Occurrences

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Treatise on Invertebrate Paleontology, Part V (1955):

  • Distinction from Amplexograptus and Lasiograptus not always easy, especially if apertural excavations are relatively wide or thecae less angularly sigmoidal or bear mesial spines.

Ruedemann (1908):

  • The principal character of Climacograptus is to be seen in the peculiar geniculation of the thecae which in their proximal part are attached parallel to the axis, then turn outward and finally again become parallel to the axis thereby placing the aperture into a more or less deep, transverse excavation between two successive thecae.

Hall (1865):

  • Simple stipes with subparallel margins, having a range of cellules on each side; axis filiform; cellules short and square; apertures apparently excavated in the margin of the stipe, and transversely oval or subquadrate; cell denticles or appendages, if present, usually on the upper side of the aperture.

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G. typicalis