Originally: Leptotrypa minimaTaxonomic History Ulrich, 1883
- 1883 Leptorypa minima Ulrich, Jour. Cincinnati Soc. Nat. Hist., VI, p. 159, pl. vi, 4, 4a
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- C5 Sequence (Lower Whitewater)
- C3 Sequence (Corryville)
- C2 Sequence (Bellevue)
Identification in Hand Sample
- Most commonly found encrusting on Orthoceras specimens.
- Cell walls thin and quite straight
- No diaphragms, usually
- Some smaller cells may be present, typically showing aborted or juvenile bryozoans
Leptotrypa minima from the Bellevue Formation of Butler Co., Ohio (MUGM 8357)
- Zoarium consisting of very thin expansions adhering parasitically to the shells of a small species of Orthoceras, which are usually entirely covered by this delicate bryozoan. The surface shows at intervals of about .08 of an inch, abruptly elevated, small, conical monticules, two or three-hundredths of an inch in diameter, and a little less in height. Their arrangement is often quite regular, in longitudinal and transverse or intersecting series. Their slopes are occupied by cells but slightly, if at all, larger than the average, while the summits often carry the apertures of a variable number of much smaller cells, which, if the specimen be worn, may give the monticules a sub-solid appearance. Cells 1/130 to 1/120 of an inch in diameter, angular, and thin-walled. The spiniform tubuli are to be observed only in well-preserved specimens by a slight elevation of the junction angles of the cells, above the general level of the cell aperture.
- In longitudinal sections, the tubes are seen to be at first somewhat prostrate, but they soon rise and proceed directly to the surface. Their walls are moderately thin and quite straight. Diaphragms are usually absent, an isolated one is, however, occasionally met with. Excepting the point of size, no difference can be detected between the ordinary tubes and the small ones mentioned in describing the monticules. On account of the filling of the tubes with the surrounding shaly matrix, the minute characters, which under other circumstances would be distinct, are often much obscured, if not obliterated.
- Tangential sections show that the angles of the cells are somewhat thickened and occupied by a small spiniform tubuli, which, if the section is taken from an inferiorly preserved example, may be overlooked. The cell walls between the angles are thin, and in the state of preservation accessible to me, show no divisional line, those of adjoining cells being apparently amalgamated with one another. A variable, though never large in number, of small cells, which our present information demands we should regard as either young or aborted, are irregularly interspersed among the ordinary cells but oftener aggregated between the cells occupying the surface monticules.
- All the specimens of this species seen by me, and their number is not less than three hundred, are without an exception, attached to a small species of Orthoceras, from two to four inches in length, and from .3 to .6 of an inch in diameter, at the larger end. The small conical monticules and flat interspaces of L. minima, will distinguish it from other species of the genu, as well as from all the rest of the parasitic Monticulipoidae of the Cincinnati group, with the exception, perhaps, of some of the species of Atactopora. These are, however, readily distinguished by their spiniferous and inflected cell-walls.