Homotrypa bassleri

Phylum: Bryozoa
Class: Stenolaemata
Order: Trepostomatida
Family: Mesotrypidae
Genus: Homotrypa
Species: Homotrypa bassleri Nickles, 1902

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Stratigraphic Occurrences


Geographic Occurrences

Map point data provided by iDigBio.
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Sequences (Formations)

  • C4 Sequence (Arnheim)

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Identification in Hand Sample

  • Zoarium Morphology: Frondose, branching; small, cylindrical or flattened branches; 4-5mm thick
  • Zoecia: Oblique; thin walled (sometimes crenulated); small, (10 in 2mm); acanthopores small, moderate in number
  • Mesozooids: Few, generally clustered
  • Monticules: Strongly tuburculated surface
  • Maculae: Larger cell apertures

Homotrypa bassleri from the Kope Formation of Brooksville, Kentucky (OUIP 159)

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McFarlan (1931)

  • Zooarium of small cylindrical or flattened branches 4-5 mm thick. Strongly tuburculated surface. Zooecia small (10 in 2mm). Acanthopores smallee, moderate in number.

Bassler (1903):

  • The small, cylindrical or slightly flattened tuberculated branches, small zooecia (ten in 2 mm.), and internally the presence of cystiphragms unaccompanied by diaphragms characterize this species.

Nickles (1902):

  • Zoarium dwarfish in habit of growth, consisting of flattened, branching fronds, which have gradually expanded from almost cylindrical stems without increasing any in thickness. No specimens showing basal portion or mode of attachment have been observed. Branches usually given off in the same plane as the frond, most often by bifurcation, though they are sometimes given off from the side. Examples used in preparing this description, none of them complete, vary from 15 to 32 mm. in height, from 5 to 9 mm. in width, and are about 3 mm. in thickness. Surface studded with low, rounded monticules, a little over one mm. in diameter, and from one to two mm. apart; rarely the monticules are almost obsolete. Apertures rather small, 9 or 10 in 2 mm., subcircular or subangular, often a little oblique to the surface; on the monticules the apertures, as is commonly the case, are a trifle larger than the others. In the axial region the zooecia have very thin walls, rather less flexuous and crinkled than is the rule in this genus; the zooecia bend rather abruptly to the peripheral region, where they have their walls much thickened after making the turn they proceed at right angles to the surface in some specimens, in others a little obliquely. No diaphragms developed in the axial region and but very few in the mature region. Cystiphragms line the upper side of the zooecia in a single row in the peripheral region, their walls attenuating toward the back, indicating that in the living state calcification was more or less incomplete. The arrangement of the layers forming the walls well shown in the enlarged view of the tangential section of a single cell, Figure 5, which shows also the appearance of the cystiphragms when cut across, and the structure of the acanthopores. Acanthopores about twice as numerous as the cells, not conspicuous; few specimens show them on the surface. A small number of irregular, angular interspaces simulating mesopores are seen in tangential sections and also on the surface.
  • This species is readily distinguished by its small, dwarfish, flattened growth, tuberculated surface and small apertures from all bryozoan found associated in the same beds, and from other species of the genus hitherto described, that detailed comparison seems unnecessary. It belongs to a section of the genus Homotrypa, which attains a wide development in the Richmond group.
  • It seems a little singular that the genus Homotrypa, while well represented in the various groups of the Trenton period, is practically lacking in the Utica and sparingly developed in the Lorraine, which from one to three characteristic species in each of its divisions, except the lowest; in the Richmond the genus becomes very prolific in species. A very large number of new species, principally from the Richmond, are known that await description.
  • This species was discovered by the writer while collecting fossils in company with Messrs. E. O. Ulrich and R. S. Bassler, in June 1899, in the vicinity of Oregonia and Lebanon, Ohio. It was at this time, also, that is was recognized that these beds form the highest division of the Lorraine. While not ranging entirely through the Warren beds of the Lorraine group, this species is one of the most characteristic fossils of these beds and is restricted to them.
  • The specific name is given in honor of my esteemed friend and former co-worker, Mr. R. S. Bassler, now of the U. S. National Museum.

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