Phylum: Bryozoa
Class: Stenolaemata
Order: Trepostomatida
Family: Amplexoporidae
Genus: Rhombotrypa Ulrich & Bassler, 1904
Cincinnatian Species: Rhombotrypa quadrata, Rhombotrypa subquadrata

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Type Species: Chaetetes quadratus (Rominger, 1866)
Species found in the Cincinnatian (Bryozoa.net)

  • Rhombotrypa multitabulata (Utgaard & Perry, 1964)
  • Rhombotrypa quadrata (Rominger, 1866)
  • Rhombotrypa subquadrata (Ulrich, 1882)

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Geologic Range
Ordovician – Devonian

Common Paleoecology
Rhombotrypa is an extinct genus of stationary colonial epifaunal filter feeders

Identification in Hand Sample:

  • Zoarium Morphology: Ramose (large)
  • Zoecia: Square (or rhombic/quadrate); Thick-walled; No Acanthopores
  • Mesozooids: Absent
  • Monticules: N/A
  • Maculae: N/A


Geographic Occurrences

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Holland (UGA Strat Lab, 2013)

  • Rhombotrypa is a large ramose form, unique in its square zooecia in the endozone, best seen in a transverse section. Zooecia are thick-walled, with numerous diaphragms in the exozone. Mesozooids and styles are absent.

Fossils of Ohio (1996):

  • Rhombotrypa Ulrich & Bassler (not illustrated) forms branching colonies. Zooecia in the axial zone have square outlines in branch cross-sections; zooecial apertures are subpolygonal on branch surfaces. There are no small polymorphs or acanthostyles.

Treatise on Invertebrate Paleontology, Part G (1953):

  • Zooecia of axial region quadrate in section

McFarlan (1931):

  • Ramose forms with zooecial tubes rhombic or quadrate in cross-section. Acanthopores usually wanting

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R. subquadrata

R. quadrata