Rhombotrypa quadrata

Phylum: Bryozoa
Class: Stenolaemata
Order: Trepostomatida
Family: Amplexoporidae
Genus: Rhombotrypa
Species: Rhombotrypa quadrata (Rominger, 1866)

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Originally:Chaetetes quadratus
Includes:Monticulipora quadrata, Monotrypella quadrataHistory: (Under Monotrypella quadrata,Nickles & Bassler, 1900)

  • 1866 Chaetetes quadratus Rominger, Proc. Acad. Nat. Sci. Philadelphia, p. 116.
  • 1881 Monticulipora (Monotrypa) quadrata Nicholson, Genus Monticulipora, p. 179, fig. 36.
  • 1882 Monotrypella quadrata Ulrich, Jour. Cincinnati Soc. Nat. Hist., V, p. 248.
  • 1888 Monticulipora quadrata James and James, Jour. Cincinnati Soc. Nat. Hist., XVI, p. 198.
  • 1889 Monotrypella quadrata Ulrich, Contr. Micro-Pal. Cambro-Sil., Part II, p. 36.
  • 1894 Monticulipora quadrata J.F. James, Jour. Cincinnati Soc. Nat. Hist., XVI, p. 198.
  • 1895 Monotrypella quadrata Whiteaves, Pal. Foss., III, p. 116.
  • 1874 Chaetetes rhombicus Nicholson, Quar. Jour. Geol. Soc. London, XXX, p. 507, pl. xxix, 11-11b.
  • 1875 Chaetetes rhombicus Nicholson, Pal. Ohio, II, p. 201, pl. xxi, 12, 12a.
  • 1876 Chaetetes rhombicus Nicholson, Ann. Mag. Nat. Hist., ser. 4, XVIII, p. 86, pl. v, 1-1b.
  • 1878 Monticulipora rectangularis Whitfield, Ann. Rep. Geol. Sur. Wisconsin for the year 1877, p. 70.
  • 1882 Monticulipora rectangularis Whitfield, Geol. Sur. Wisconsin, IV, p. 249, pl. xi, 11, 12.
  • 1878 Monticulipora multituberculata Whitfield, Ann. Rep. Geol. Sur. Wisconsin for the year 1877, p. 71.
  • 1882 Monticulipora multituberculata Whitfield, Geol. Sur. Wisconsin, IV, p. 250, pl. xi, 9, 10.
  • Cincinati (Richmond): A common and characteristic species ofthe Richmond group in Ohio, Indiana, Illinois, Wisconsin, and Manitoba.

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Stratigraphic Occurrences


Geographic Occurrences

Map point data provided by iDigBio.
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Sequences (Formations)

  • C6 Sequence (Upper Whitewater, Elkhorn)
  • C5 Sequence (Saluda, Lower Whitewater, Liberty, Waynesville)

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Identification in Hand Sample

  • Zoarium Morphology: Ramose (large) to lobate; diameter: 4-10 mm
  • Zoecia: Square (or rhombic/quadrate); Thick-walled; 7-8 in 2mm; No Acanthopores
  • Mesozooids: Few, restricted to maculae
  • Monticules: Surface smooth
  • Maculae: Or larger apertures; slightly elevated.

Rhombotrypa quadrata (MU-22071) from the Waynesville Formation of Butler County

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McFarlan (1931):

  • R. quadrata: Zooarium ramose to lobate, diameter branches 4-10 mm. Surface smooth or with maculae of larger apertures slightly elevated. Acanthopores commonly described as absent but distinct, rounded clear spots occur at the junction angles. Mesopores absent. 7-8 zooecia in 2 mm.
  • This species can be distinguished from Rhombotrypa subquadrata by its larger form, (R. subquadrata’s branches are generally 2-3mm in diameter), and by the absence of mesopores (R. subquadrata has mesopores)

Davis (1998):

  • Unique in the rhombic or quadratic cross-section of the zooecia.

Foerste (1924):

  • Specimens with branches attaining a diameter of 12 mm. Eleven cells occupy a length of 3 mm. Generic character may be recognized in the field most readily by breaking a branch across and moistening the end of the branch. In this case, the central parts of the branch will appear divided into minute squares by equidistant lines that cross each other nearly perpendicularly. On closer inspection a similar tendency toward arrangement in rectangularly crossing series is noticed among the apertures on the surface, cells being to some extent in groups, members of the same group showing the rectangular outlines and arrangement.
  • Locality and Horizon. Clay Cliffs (No. 8551); northwest of Manitowaning; north of Meaford; Streetsville; and on Snake island. Form the Richmond, chiefly the Waynesville member. The species occurs practically wherever the Richmond is known and at almost every horizon.

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