Rafinesquina ponderosa

Classification
Phylum: Brachiopoda
Class: Strophomenata
Order: Strophomenida
Family: Rafinesquinidae
Genus: Rafinesquina
Species: Rafinesquina ponderosa (Hall)

Geologic Range
Ordovician (Caradoc-Ashgill)

Stratigraphic Occurrences

R.ponderosa

Geographic Occurrences

Map point data provided by iDigBio.

Stratigraphic Distribution

C5 Sequence (Waynesville)
C2 Sequence (Bellevue)

Identification in Hand Sample

    • Difficult to distinguish from R. alternata; the two species may be synonymous
    • Thinner, less visible striae (no sharp contrast between coarse and fine)
    • Large cardinal process
    • Larger in size than R. alternata, usually ranging in size from 50-60 mm
Rafinesquina_ponderosa_800px

Rafinesquina ponderosa from Arnheim formation of Franklin County, Indiana (OUIP 1012)

Published Descriptions

Davis (1998):

  • Articulate brachiopod. Interior of brachial valve – forked cardinal process and muscle impressions. Exterior of pedicle valve; interior of pedicle valve – note teeth and fan – shaped muscle impression. Entire Cincinnatian.

McFarlan(1931):

  • A large, massive variety with more deeply excavated muscle scars, and vascular markings and unusually large cardinal process. Width commonly 50-60 mm. Common in the Bellevue at Cincinnati also in the upper Fairmount of the southern Bluegrass.

Hall(1892):

  • Shells normally concavo-convex. Surface ornamented by radiating striae, of alternating size, crossed and crenulated by finer concentric striae. Cardnial margins without denticulations. Interior of the pedicle-valve with the muscular area not strongly limited, consisting of two broad flabelate diductor scars enclosing 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 brachial 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 arborescent 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.