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

Taxonomic Details

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)

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

[leaflet-map lat=39 lng=-84.5 zoom=7 width=575 height=250 align="right"]

Published Description

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

R. subquadrata

R. quadrata