Rafinesquina

Classification
Phylum: Brachiopoda
Class: Strophomenata
Order: Strophomenida
Family: Rafinesquinidae
Genus: Rafinesquina Hall & Clarke, 1892
Cincinnatian species: Rafinesquina alternata, Rafinesquina nasuta, Rafinesquina ponderosa

Geologic Range
Ordovician (Caradoc-Ashgill)

Common Paleoecology
Rafinesquina is an extinct genus of facultatively mobile, epifaunal suspension feeders

Characteristics of the Genus

  • Concavo-convex
  • Radiating striae which alternate in size.
  • Finer growth lines crossing the radiating striae.
  • Straight hinge line
  • Bilobed cardinal process
  • Ventral valve does not have a strongly limited muscle area,
  • Two fan-shaped diductor muscle scars, with an elongated, more definite adductor muscle scar.
  • There are a series of irregular furrows which radiate from the anterior margin of the muscular area.

Geographic Occurrences

Published Descriptions

Treatise on Invertebrate Paleontology, Part H, Vol. 2 (2000):

  • Concavo-convex profile, with dorsal valve initially very gently concave but with increased curvature anteriorly; unequally parvicostellate ornament; pseudodeltidium, larger chilidium filling delthryium; relatively short, divergent dental plates; ventral muscle field flabellate, with no bounding ridges; ponderous triangular cardinal process lobes in adults flanked by sort delicate socket ridges often with crenulations; weak dorsal median septum present, merging posteriorly with low myophragm. Cosmopolitan

Fossils of Ohio (1996):

  • A large concavo-convex strophomenid brachiopod. The outline is semicircular and is truncated by a straight hinge line. Width and length are approximately equal. Ornamentation consists of numerous fine ribs that radiate from the umbones of both valves toward the commissure. The dorsal valve is concave and the pedicle valve is convex, in contrast to Strophomena, which, for most of its length, has the dorsal valve convex and the ventral concave. The dorsal-valve interior of Rafinesquina  has a massive, bilobed cardinal process adjacent to the hinge line. The interior of the ventral valve has broad, poorly defined muscle scars.Rafinesquina has been recorded from the Cincinnatian Series.

Caster, Dalve & Pope (1961):

  • The edrioasteroids are another class of animals belonging to the marine echinoderms. They range in time from the Lower Cambrian to the Mississippian. These animals are rather rare in the Cincinnatian but may be occasionally found by diligent search of the Bellevue and Corryville members. The mode of life of the edrioasteroids was dominantly sessile, that is, they generally lived on the bottom or attached to a suitable hard object. The outside surface of the pedicle valve of Rafinesquina seems to have been their favorite site of attachment and consequently should always be carefully studied. Because of their rarity and beauty, good edrioasteroids are always prize finds.

McFarlan (1931):

  • Concavo-convex striated shell with straight hinge line and well developed cardinal area. Ventral valve convex with faintly delimited flabellate diductors enclosing elongate adductors. Cardinal process bilobed.

New York State Museum (1892):

  • Shells normally Concavo-convex. Surface ornamented by radiating striae, of alternating size, crossed and renulated by finer concentric striae. Cardinal margins without denticulations. Interior of the pedicle-valve with the muscular area not strongly limited; consisting of two broad flabellate diductor scars inclosing an elongate, more distinctly defined adductor. The faintness of the limitation of this area is in marked contrast to the sharply defined muscular area in the corresponding valve of Leptaena  in the dorsal valve the cardinal process is more closely sessile than in Leptaena, and there is frequently a linear callosity between the branches. The posterior adductor scars have the aborescent markings of Leptaena rhomboidalis, and these impressions are the only ones well defined, the anterior scars being narrow and rarely retained with distinctness. From the anterior margin of the muscular area radiates a series of irregular furrows and nodose ridges, which are to some extent of vascular origin.

R. alternata


R. nasuta


R. ponderosa