Amplexopora septosa

Phylum: Bryozoa
Class: Stenolaemata
Order: Trepostomatida
Family: Amplexoporidae
Genus: Amplexopora
Species: Amplexopora septosa (Ulrich, 1879)

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Originally: Atactopora septosa
Includes: Amplexopora multispinosaHistory: (Nickles & Bassler, 1900)

  • 1879 Atactopora septosa Ulrich, Jour. Cincinnati Soc. Nat. Hist., II, p. 125, pl. xii, 7-7c.
  • 1882 Amplexoporaseptosa Ulrich, Jour. Cincinnati Soc. Nat. Hist., V, p. 255.
  • 1888 Monticulipora septosa James and James, Jour. Cincinnati Soc. Nat. Hist., X, p. 180.
  • 1894 Monticulipora septosa J.F. James, Jour. Cincinnati Soc. Nat. Hist., XVI, p. 203.
  • Cincinnati (Utica and Lorraine): Covington and Newport, Kentucky; Cincinnati, Ohio.

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Stratigraphic Occurrences


Geographic Occurrences

Map point data provided by iDigBio.
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Sequences (Formations)

  • C2 Sequence (Fairview: Fairmount)
  • C1 Sequence (Clays Ferry/Kope: McMicken, Southgate, Economy/Fulton)

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Identification in Hand Sample

  • Zoarium Morphology: Ramose, of smooth cylindrical stems; 5-10 mm in diameter branches
  • Zoecia: Polygonal, with numerous small acanthopores
  • Mesozooids: Few, restricted to maculae
  • Monticules: None
  • Maculae: Composed of larger apertures and some mesopores. Sometimes a little bit elevated.

Amplexopora septosa from Mt. Hope formation of Dearborn County, Indiana (CMCIP 23950)

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Ulrich (1879) under Atactopora septosa:

  • A ramose species, growing from an expanded base, by which it is attached to foreign bodies. Branches bearing considerable resemblance to those of Chaetes (Monticulipora) puchellus or fletcheri. Surface exhibiting low, broad and rounded tuberosities; which are placed at distances apart of about one line, and carry groups of larger tubes than those of the ordinary size. Tubes small polygonal, quite regularly arranged, without any minute interstitial cells; walls thin; about eight of the tubes, of average size, occupy the space of one line; about six of the tubes of larger size, occupy the same space. Pseudo-septa well developed, more easily detected in slightly worn specimens than in those perfectly preserved; from one to five in each tube.
  • In longitudinal sections the tubes are seen to be nearly vertical in the middle of the branch; here they have very thin walls and are crossed by excessively thin and remote tabulae; they then bend abruptly outward, and as the surface is approached the tabulae are more closely set, and the walls become stouter; here also the pseudo-septa make their appearance, as is demonstrated by the darker lines which extend parallel with, and between, the true walls of the tube. The diaphragms are so thin that they can easily be overlooked.
  • In tangential sections, the pseudo-septa are very conspicuous and usually, number three or four in each tube. Transverse sections show the tubes in the center of the branch, to be polygonal, without minute intercellular tubuli, and with very thin walls.
  • From an external examination, when the pseudo-septa are not visible, it is not an easy matter to distinguish specimens of this species from certain varieties of Chaetes (Monticulipora) pulchellus; but when worn there is no difficulty, as the septa, when viewed through a hand lens, give a peculiar and characteristic appearance to the specimens. Of course, tangential sections will immediately demonstrate their distinctness. The ramose growth of the species will distinguish it from the other species of Atactopora.

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