Ambonychia robusta

Phylum: Mollusca
Class: Bivalvia
Order: Pterioida
Family: Ambonychiidae
Genus: Ambonychia
Species: Ambonychia robusta (Miller, 1880)

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Formerly: Byssonychia robusta
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Stratigraphic Occurrences

A. robusta_strat

Geographic Occurrences

Map point data provided by iDigBio.
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Sequences (Formations)

  • C6 Sequence (Elkhorn)
  • C5 Sequence (Whitewater, Liberty, Waynesville)

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Identification in Hand Sample

  • Shell is large, very ventricose. Distinctive narrow radial plications.
  • Beak acute, triangular
  • Anterior side flattened and depressed
  • Muscular impression high in this species

Ambonychia robusta from Waynesville formation of Warren County, Ohio (left, OUIP 1294) and Franklin County, Indiana (center and right, OUIP 1565)

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Davis (1998) :

  • Pelecypod. Large, imperfect specimen, showing convex form and distinct plications. Waynesville to Whitewater.

Fossils of Ohio (1996):

  • The genus Ambonychia, which ranges from Middle to Upper Ordovician, is represented in the Ordovician of Ohio by A. robusta Hall. This medium-sized species has narrow radial plications.

Miller (1880) :

  • Shell large, very ventricose, anterior side flattened and depressed in the region of the byssus; beaks acute, triangular; posterior wing, short, muscular impression high, and surface marked by about forty simple radii, which are crossed by fine concentric striae.This species is distinguished by its large size, triangular beaks, flattened and depressed anterior side, and high position of the muscular impression. The specimens are quite variable in size, but a medium specimen has a” height from base to beak of 2 6-10 inches and thickness of 1 8-10 inches. Specimens having the shell quite well preserved, occur in the upper part of the Hudson River Group, near Osgood, Indiana, where I collected the type specimens. And I refer the large casts having a flat anterior side, which occur at Richmond, Indiana, to the same species, though the*y have a greater height in proportion to their length and thickness.

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