Batostoma varians

Phylum: Bryozoa
Class: Stenolaemata
Order: Trepostomatida
Family: Trematoporidae
Genus: Batostoma
Species: Batostoma varians (James, 1878)

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Originally: Chaetetes varians
Referred to as: Monticulipora varians
Includes: Batostoma variabile

Taxonomic History (Nickles & Bassler, 1900)

  • 1878 Chaetetes varians James, Paleontologist, No. 1, p. 2.
  • 1881 Monticulipora (Chaetetes) varians James, Paleontologist, No. 5, p. 36.
  • 1888 Monticulipora varians James and James, Jour. Cincinnati Soc. Nat. Hist., X, p. 177, pl. ii, 4 a, b.
  • 1894 Monticulipora varians J.F. James, Jour. Cincinnati Soc. Nat. Hist., XVI, p. 199.
  • 1890 Batostoma variabile Ulrich, Geol. Surv. Illinois, VIII, p. 460, pl. xxxv, 4-4e, 5 (not 5a), pl. xxxvi, 1.
  • 1894 Batostoma variabile J.F. James, Jour. Cincinnati Soc. Nat. Hist., XVI, p. 200.

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Stratigraphic Occurrences


Geographic Occurrences

Map point data provided by iDigBio.
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Sequences (Formations)

  • C5 Sequence (Saluda, Lower Whitewater, Liberty, Waynesville)
  • C4 Sequence (Arnheim)

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Identification in Hand Sample

  • Zoarium Morphology: Dendroid, with irregularly thickened/nodulose branches; diameter: 5-10mm
  • Zoecia: Circular or oval (~6 in 2mm density); acanthopores small, rather numerous
  • Mesozooids: Separate zooecia
  • Monticules: N/A
  • Maculae: N/A

Batostoma varians from the C5 Waynesville Formation of Waynesville, Ohio (OUIP 1438)

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Holland (UGA Strat Lab 2013):

  • Has thin-walled, angular zooecia, with few mesopores, sparse diaphragms, and a subfrondescent zooarium.

Davis (1998):

  • Externally like Batostoma jamesi; internally, B. varians has fewer mesopores

Bassler (1905):

  • The earliest description of this species was sufficient for its recognition especially since it was compared with Chaetetes (now Batostoma) jamesi Nicholson, of which good figures and a description had appeared some years before. James’s description of 1881 also gives a fair idea of the form and comparisons with the related B. jamesi. Ulrich’s definition and figures of Batostoma variabile prove upon further investigation to be founded upon at least two distinct species of Batostoma, one of which as indicated above is synonymous with B. varians, while the second is here recognized and redefined as B. variabile. The geological occurrence of the two species is quite different, B. varians ranging from the Arnheim formation to and through the Whitewater formation of the Richmond group, and B. variabile being a characteristic fossil of the uppermost beds of the same group.
  • Comparing B. varians and B. jamesi, the former is found to have thin-walled, angular, instead of oval, thick-walled zooecia, few and irregularly placed instead of numerous mesopores, fewer diaphragms, and a lobate or subfrondescent zoarium instead of a regularly ramose one as in the latter species. For good measure of both the internal and external characters of B. varians, the student if referred to those mentioned above under the citation of B. variabile.

Nickles (1905):

  • Zoarium visible in form, encrusting, lobate, ramose or subfrondescent. Surface smooth, with scarcely elevated clusters of larger cells. Apertures angular, averaging 6 in 2 mm. Mesopores angular, varying in number, generally few. Acanthopores numerous, usually in the angles between the zooecia. Zooecial tubes with thin, slightly flexuous walls and few diaphragms in the axial region; with walls thickened, and several diaphragms in the narrow mature region which the zooecia enter by a gradual curve.

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