Escharopora hilli

Phylum: Bryozoa
Class: Stenolaemata
Order: Cryptostomata
Genera: Escharopora
Species: Escharopora hilli (James, 1878)

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History (Nickles & Bassler, 1900)

  • 1878 Ptilodictya hilli James, Paleontologist, No. 1, p. 4.
  • 1882 Ptilodictya hilli Ulrich, Jour. Cincinnati Nat. Hist., V, pl. vii, 7, 7a.
  • 1885 Ptilodictya hilli Nettleroth, Kentucky Fossil Shells, p. 30, pl. xxxv, 1, 2, 4, 5.
  • 1893 Escharopora hilli Ulrich, Geol. Minnesota, III, p. 167.

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Stratigraphic Occurrences


Geographic Occurrences

Map point data provided by iDigBio.
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Sequences (Formations)

  • C3 Sequence (Corryville, Mount Auburn)
  • C2 Sequence (Mount Hope, Fairmount, Bellevue)

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Identification in Hand Sample
E. hilli

  • Zoarium Morphology: Unbranching, simple “frond”; more robust: width up to 4mm, length up to 13 mm, thickness 2-3mm
  • Zoecia: Sub-elliptical; arranged diagonally in intersecting series (angles between 50* and 80*)
  • Mesozooids: Few
  • Monticules: Conspicuous, elevated
  • Maculae: Several mm apart, composed of larger apertures

Escharopora hilli from the Lorraine Formation of Boyle Co., Kentucky (CMC 18194)

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Holland (UGA Strat Lab, 2013):

  • Like E. falciformis, but with prominent transverse ridges.

McFarlan, (1931):

  • Greater width and irregularity than E. maculata

Bassler (1906):

  • The specific character of this fine species was pointed out by Mr. James in his description as follows: “The marked and decided difference between this species and P[tilodictya] faciformis Nicholson lies in the prominent transverse ridges.” The zoarium in this form, however, is usually wider and stronger than in Echaropora falciformis, but as already mentioned the transverse ridges are the most obvious difference. These ridges are formed by the elevated maculae, which are so transversely elongated that they become confluent.

Nettelroth (1887):

  • (Escharopora hilli as Ptilodictya hilli):
    Zoarium digitate, the number of prongs not known; the specimen before me shows one complete branch, which deflects from the original stem, just above the wedge-shaped articulating process, out of the sharp edge, and extending in the same plane with the main stems. On one of the broad sides of the main stem, and in its center, line, are two protuberances, the one opposite the center line of the deflecting branch, and the other about one-fourth of an inch above it, which appear to be the buds of two new branches, but whose positions make it somewhat doubtful, inasmuch as those new stems would leave the plane of the two existing prongs. In similar species, as P. ramosa and P. briareus, the branches start always from the sharp edge, and I do not doubt that the same is the case with P. hilli. We may, therefore, assume, that very few branches are formed. This species is generally found in more or less straight, thin strips, of different width, the cross sections of which are either acutely elliptical or elliptic-lanceolate. Both sides are entirely equal; they are most convex in their central line, from where they slope in a regular but gentle curve to the lateral margins, where the surfaces of both sides meet at a very acute angle. The surfaces of both sides are covered by transverse, sharply angular ridges, with interspaces of about twice their own width. Some of these plications cross the branches from one edge to the other in a straight line, rectangular with the margin. While the course of others is somewhat oblique, with others again crossing the surface only partly. These shorter ribs are always intercalated, and never produced by bifurcation. The whole zoarium is covered by closely arranged rhomboidal cells of about equal size, the walls of which form nearly straight lines, cross each other only obliquely. The largest specimen in my possession measures nearly four inches in length, by more than an inch in width; in its whole extent it does not show any branch; it has thirteen transverse ribs in the space of an inch. A smaller specimen measures one inch and three-eighths in length, by one-fourth of an inch in width, with nineteen cross ribs in the space of an inch.

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