Rhynchotrema dentata

Classification
Phylum: Brachiopoda
Class: Rhynchonellata
Order: Rhynchonellida
Family: Rhynchotrematidae
Genus: Rhynchotrema
Species: Rhynchotrema dentata (Hall)

Stratigraphic Occurrences

R.denata_strat

Geographic Occurrences

		
Map point data provided by iDigBio.

Stratigraphic Description

Sequences (Formations)

  • C5 Sequence (Whitewater, Liberty, Waynesville)

Identification in Hand Sample

  • Small and subelliptical when viewed from the side
  • Pretty similar length to breadth (ratio – 5:6)
  • 7 to 8 simple, angular and radiating plications on each valve
  • Two plications on the sinus of the dorsal valve, one on the sinus of the ventral valve
  • Concentric growth lines can be seen under microscope
  • Strongly arched ventral valve
  • Pedicle valve compressed in the middle
  • Fold starts as narrow shallow sinus at beak, then becomes elevated above the
  • General surface fo the shell at a 1/3 the distance from beak to anterior margin
Rhynchotrema_dentata_800px

Rhynchotrema dentata from Waynesville formation of Franklin County, Indiana (OUIP 1604)

Published Description

Holland (1997):

  • One Plication in the sulcus

Denison Scientific Association (1910-1911):

  • Rhynchotrema dentata, as represented in the upper part of the Whitewater bed, at Richmond, Indiana, is characterized by greater convexity of both valves. The middle part of the pedicle valve usually is not flattened and then partly reflexed toward the anterolateral angles, as is more frequently the case in large specimens of the Arnheim variety.

Weller (1903):

  • Shell small, transversely subelliptical in outline, the proportions of length to breadth being about as five to six; obtusely angular at the beak. Each valve marked by seven or eight simple, angular, radiating plications on each side of the fold and sinus, with one plication in the bottom of the sinus of the pedicle valve and two upon the fold of the brachial valve. The interlocking, angular plications give to the anterior and lateral margins of the shell, in an anterior view, a sharply zig-zag outline. Crossing the plications, and parallel with the margin, are fine, concentric lines of growth, which can only be detected by the aid of a magnifying glass. Pedicle valve strongly arched from beak to front, the plications bounding the sinus very prominent, the lateral slopes concave, so that the valve just at the beak and a little in front is subcarinate. Sinus not continuous to the beak. At the beak the median plication is slightly elevated above the two adjacent ones, but in passing anteriorly it soon becomes depressed below them, and at the anterior margin occupies the bottom of the rather profound sinus. Brachial valve less convex than the opposite one, flattened in the middle and passing in a convex curve to the margin all around, except directly in front in the area occupied by the median fold. The fold, starting at the beak as a narrow, shallow sinus, becomes elevated above the general surface of the shell at a point about one-third the distance from the beak to the anterior margin.