Homotrypa hospitalis

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

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Originally: Prasopora hospitalisTaxonomic History (Nickles & Bassler, 1900)

  • 1881 Monticulipora (Prasopora) selwynii var. hospitalis Nicholson, Genus Monticulipora, p. 209, fig. 45..
  • 1882 Prasopora hospitalis Ulrich, Jour. Cincinnati Soc. Nat. Hist., V, p. 237.
  • 1888 Monticulipora hospitalis James and James, Jour. Cincinnati Soc. Nat. Hist., XI, p. 26.
  • 1888 Monticulipora hospitalis var. neglecta James and James, Jour. Cincinnati Soc. Nat. Hist., XI, p. 27, pl. i, 3.
  • 1896 Monticulipora hospitalis var. neglecta J.F. James, Jour. Cincinnati Soc. Nat. Hist., XVIII, p. 124.

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Stratigraphic Occurrences

Geographic Occurrences

Map point data provided by iDigBio.
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Sequences (Formations)[/accordion] [/accordions]

Identification in Hand Sample

  • Zoarium Morphology:Small, more or less rounded zoarium.
  • Zoecia:Have numerous acanthopores that are lined with cystiphragms, and are separated by closely tabulated mesopores.
  • Mesozooids:Closely tabulated.
  • Monticules:Moderately elevated rounded monticules 3 mm. apart.
  • Maculae:

Homotrypa hospitalis from the Richmondian Formation of Cincinnati, Ohio (CMC 70731)

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Holland (UGA Strat Lab, 2013):

  • Massive growth form, numerous mesopores with closely spaced diaphragms, numerous and strong acanthopores, rounded zooecia with numerous cystiphragms and diaphragms.

McFarlan (1931) (in reference to Homotrypella hospitalis):

  • This species is exceptional for the genus in its massive, hemispherical form, commonly attached to brachiopod or other shells, and 2-4 cm. in diameter. Surface smooth or with maculae of larger apertures slightly elevated. Mesopores numerous, closely tabulated. Acanthopores numerous and strong. Cystiphragms line the zooecial tubes. In assigning this species to Homotrypella instead of Prasopora, only a very short region at the proximal end which is free of cystiphragms may be recognized as the (im). The difference in development of acanthopores is distinct.

Bassler (1911):

  • Zooarium massive, growth beginning upon some foreign object and continuing until a more or less regular, rounded colony results. Surface marked by moderately elevated, rounded monticules, 3 mm. apart. Under a hand lens, the surface is seen to be finely spinulose because of numerous acanthopores. The characteristic features distinguishing this from most associated bryozoans are seen either in thin sections or in fractures moistened and examined under a strong hand lens. In either case, the numerous cystiphragms lining the zooecial walls and the closely tabulated mesopores are evident, while the abundant acanthopores are seen to best advantage in tangential sections. Cystiphragms are found most often lining one side of the zooecia, but sometimes both sides show them. Ordinarily thirty cystiphragms may be counted in two mm., while the mesopores hold approximately the same number of straight diaphragms. In deep tangential sections both the zooecia and mesopores are thin walled and polygonal, but as the surface is approached, the zooecial walls thicken at the expense of the mesopores. In the outermost parts of the mature region, calcareous tissue is often developed in the mesopores to such an extent that the latter is obliterated. Eight zooecia in two mm.

Nicholson (1881):

  • The type form of M. selwynii occurs in the Trenton Limestone of Canada; but there is found in the Cincinnati formation of Ohio a form which possesses a very similar internal structure, and which I propose, in the meanwhile, to separate as a distinct variety, under the name of M. selwynii, var. hospitalis, Nich. In its habit and size, and in some of the minor points of its organization, this form differs considerably from the typical examples from the Trenton Limestone, which I have selected as the basis for the preceding specific diagnosis; but as it is clearly a very close ally of M. selwynii, I prefer to regard it at present as nothing more than a very strongly marked variety.
  • M. selwynii, var. hospitalis, is invariably an attached form, all the numerous examples which I have seen being fixed to the exterior of the shells of Brachiopods. In from they are hemispheric, rarely nearly globular, and their general size is from six to ten lines in diameter, and from three to four to seven or eight lines in height. Tangential sections show a close correspondence in general structure with the type-form of M. selwynii, from the Trenton Limestone. The corallum is composed of large and small corallites, the former being oval or circular in shape, and varying from 1-50th to 1-70th inch in diameter, each showing an eccentrically perforated tabula. The small corallites are numerous, sub-angular, and wedged in between all the larger tubes, occasionally being aggregated into star-shaped groups or ‘maculae’. Besides the normal two kinds of corallites, a considerable number of thick-walled hollow spines (‘spiniform corallites’) may be observed, which I have not detected as present in the examples from the Trenton Limestone.
  • Vertical sections show the same marked difference in the tabulation of the large and small corallites and has been previously noticed in the type-form, with some differences. The large tubes are always double tabulate, one set of tabulae forming a series of larger lenticular vesicles, the convex sides of which as directed inwards towards the center of the visceral chambers, while the remaining tabulae are horizontal and remote, and extend from the lateral wall of the corallite to the inner margin of the above-mentioned vesicles. In some of the tubes we may occasionally notice the convex tabulae to form isolated vesicles, as they usually do in the specimens from the Trenton Limestone; but they are more commonly so opposed to one another as to form vertical rows of lenticular cells, the inner margins of which unite so as to constitute an apparent median septum to the corallite. The small corallites are uniformly furnished with numerous complete, horizontal tabulae. Upon the whole, I have little doubt that the specimens now described from the Cincinnati Group of Ohio are not specifically separable from the true M. selwynii of the Trenton Limestone.

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