Homotrypa dawsoni

Phylum: Bryozoa
Class: Stenolaemata
Order: Trepostomatida
Family: Mesotrypidae
Genus: Homotrypa
Species: Homotrypa dawsoni (Nicholson, 1881)

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Originally: Monticulipora (Heterotrypa) dawsoni Taxonomic History (Nickles & Bassler, 1900)

  • 1881 Monticulipora (Heterotrypa) dawsoni Nicholson, Genus Monticulipora, p. 141, pl. v, 3-3f.
  • 1882 Monticulipora dawsoni Ulrich, Jour. Cincinnati Soc. Nat. Hist., V, p. 241.
  • 1888 Monticulipora dawsoni James and James, Jour. Cincinnati Soc. Nat. Hist., XI, p. 15.
  • 1895 Monticulipora dawsoni J.F. James, Jour. Cincinnati Soc. Nat. Hist., XVIII, p. 68.

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Stratigraphic Occurrences


Geographic Occurrences

Map point data provided by iDigBio.
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Sequences (Formations)

  • C5 Sequence (Waynesville)

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Identification in Hand Sample

  • Zoarium Morphology: Frondose, branching; flattened branches
  • Zoecia: Oblique; thin walled (sometimes crenulated)
  • Mesozooids: Few, generally clustered
  • Monticules: Low rounded monticules
  • Maculae: Larger cell apertures

Homotrypa Dawsoni unknown location. (CMC 21326)

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Davis (1998)

  • Characterized by low, rounded monticules, flattened branches, and diaphragms present in immature parts of zooecia.

Bassler (1903):

  • With the exception of one feature, this fine species was well described and figured by Nicholson. His vertical section (Plate V, fig. 3e) shows complete diaphragms in the mature region, and in his description he says of that region, “a moderate number of complete horizontal tabulae being developed;” and again, “tabulae are in all cases complete and approximately horizontal.” and again, “tabulae are in all cases complete and approximately horizontal.” The normal condition of the species, as seen in vertical sections, is shown in our figure 9 of Plate XXV. The cystiphragms are here seen to be large and rather irregularly developed or altogether absent, but in the zooecial tubes of the maculae a full series is usually present. Diaphragm-like structures occur, particularly in the outer part of the peripheral region, but these are probably cystiphragms, which, extending almost across the cell cavity, give in certain sections the appearance of true diaphragms. In the section, figured by Nicholson, apparently, all of the cystiphragms presented this appearance. An entire zoarium, with its broad frond and prominent, closely set monticules, is a handsome cabinet specimen.

Ulrich (1882):

  • Besides the two species next described, the Cincinnati Group furnishes at least three other distinct forms, having the characters of this genus. One of these was described and figured by Nicholson, under the name of Monticulipora (Heterotrypa), dawsoni (“Genus Monticulipora,” p. 141, Plate V., figs. 3.3f, 1881). His figures of that species fail to represent two of the most important characters, nor are the mentioned in his description, viz: the connecting foramina, and cystoid diaphragms. I feel confident that his sections were prepared from a portion of a frond not fully matured, since his figures and description of the internal characters of the species apply in all respects to sections prepared by me from examples in that condition. In a tangential section of a fully matured specimen, cutting the tubes just below the surface, the walls of same have a thickness about equal to those of H. curvata, as represented by fig. 7d, Plate X., and the connecting foramina (clearly shown in one of my sections), are precisely like those piercing the walls of the tubes in H. oblique (Plate X., fig. 6b). The cystoid diaphragms are large, and developed in only a minority of the tubes, and in this character H. dawsoni differs from all the other species of the genus. This species if further characterized by its frondescent growth and remarkably prominent and closely arranged monticules.

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