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Oepikina minnesotensis

Strophomenata - Strophomenida - Strophomenidae


This is it's own species! It needs to be separated from Rafenisquina minnesotensis.

Strophomena minnesotensis was named by Winchell (1881) [= Leptaena deltoidea (Conrad. Owen 1852, Report of a geological survey of Wisconsin, Iowa, and Minnesota, p. 629, tab. 21, fig. 10 (not the middle figure) = Strophomena incrassata Safford (not Hall). HALL, 1883, New York State Geologist Second Ann. Rept., pl. 38(8), fig. 2 (not figs. 1, 3-5). (from Salmon 1942)].

It was recombined as Rafinesquina minnesotensis by Hall and Clarke (1892), Winchell and Schuchert (1895), Grabau and Shimer (1907), Bassler (1915) and Hume (1925); it was recombined as Opikina minnesotensis by Salmon (1942); it was recombined as Oepikina minnesotensis by Bretsky and Bretskey (1975) and Pope (1982).

Synonymy list
YearName and author
1881Strophomena minnesotensis Winchell p. 120 figs. pl. 4 f. 24 & 25
1892Rafinesquina minnesotensis Hall and Clarke p. 283
1895Rafinesquina minnesotensis Winchell and Schuchert pp. 401-403 figs. pI. 31, figs. 25-26, 29
1907Rafinesquina minnesotensis Grabau and Shimer p. 215 fig. 252
1915Rafinesquina minnesotensis Bassler p. 1022
1925Rafinesquina minnesotensis Hume
1942Opikina minnesotensis Salmon pp. 592 - 593 figs. Plate 87, figures 5-11
1975Oepikina minnesotensis Bretsky and Bretskey pp. 9, 18 figs. pl. 1-2
1982Oepikina minnesotensis Pope pp. L6-L17 figs. Plate 1, figures 1-14; plate 2, figures 1-12; plate 3, figures 1-19; text-figures 1-11

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phylumBrachiopodaCuvier 1805
subphylumRhynchonelliformeaWilliams et al. 1996
classStrophomenataWilliams et al 1996
orderStrophomenidaOpik 1934
superfamilyStrophomenoideaKing 1846
familyStrophomenidaeKing 1846
subfamilyFurcitellinaeWilliams 1965

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

E. S. Salmon 1942Shell relatively small, outline evenly and narrowly rounded; widest at or anterior to the hinge line; cardinal angles bluntly rounded, about 90˚. Convexity high; posterior gently rounded, anterior a long straight slope. Geniculation sharply rounded but not angular, about 10 mm. from the beak, forming an angle of about 100˚.

No surface markings are visible on the specimens believed to be the syntypes, which are silicified internal molds of pedicle valves. However, other specimens from the same horizon and locality that appear to be specifically identical with the types have very fine costellae of alternating sizes, and the shell is very finely pseudopunctate.

The pedicle muscle area is nearly circular and occupies about one-half the interior surface. The dental lamellae diverge at an angle of about 120?; the lateral and anterior margins of the muscle area are very faintly marked. The adductor tracks consist of a relatively wide ridge, which is highest at the anterior end. The diductor scars are marked by fine radial ridges. The entire visceral area is limited by a low circular ridge. The interior of the brachial valve shows the median and two pairs of lateral septa, which are highest at the anterior ends, and a sharp ridge around the anterior and lateral margins of the visceral area.
J. K. Pope 1982Shells relatively small. Outline semicircular, slightly transverse or slightly elongate. Cardinal extremities orthogonal, rounded, or slightly alate. Convexity variable, low and smoothly curved to high with rounded geniculation. Costellae fine, uniform to weakly unequal. Teeth strong, transversely grooved. Diductor muscle scars oval, slightly impressed. Ventral adductor muscle scars on elongated ridges. Ventral valve with low submarginal rim. Dorsal trans-muscle ridges straight or with slight angular bend; highest toward anterior. Marginal rim of dorsal valve conspicuous.