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Ctenodonta spjeldnaesi

Bivalvia - Protobranchia - Ctenodontidae

Ctenodonta spjeldnaesi was named by Soot-Ryen and Soot-Ryen (1960) [DISTRIBUTION: Middle Ordovician; Norway.]. Its type specimen is P.M.O. 40308, a shell, and it is a 3D body fossil.

It was recombined as Similodonta spjeldnaesi by Soot-Ryen and Soot-Ryen (1964) and Toni (1975).

Synonymy list
YearName and author
1960Ctenodonta spjeldnaesi Soot-Ryen and Soot-Ryen pp. 87 - 89 figs. Plate I, figs. 3-6, textfig. l.
1964Similodonta spjeldnaesi Soot-Ryen and Soot-Ryen p. 498
1975Similodonta spjeldnaesi Toni pp. 138 - 139 fig. 2C

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EubilateriaAx 1987
orderProtobranchiaPelseneer 1889
superorderNuculiformiiDall 1889
orderSolemyidaNewell 1965
superfamilySolemyoideaAdams and Adams 1857
familyCtenodontidaeDall 1889
genusCtenodontaSalter 1852

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.

H. Soot-Ryen and T. Soot-Ryen 1960Shell small, rounded triangular, slightly langer than high. Umbones full but not much inflated, opisthogyre. Umbonal angle blunt. Anterodorsal margin curvcd and inflected with a more or less distinct anteroventral angle, ventral margin rounded and posteroventral corner broadly rounded. Posterodorsal margin concave to straight with the lower part somewhat protruding. Parallel to the anterodorsal margin there is a more or less distinct sulcus. Sculpture consisting of somewhat irregular concentric lines with broad interspaces, 5-6 lines on 2 mm in the middle part of the valve. On the internal casts there are several growth lines along the margins. Ringe teeth in two series (textfig. 1) , c.9 proximal anterior teeth, lamelliform and nearly vertical to the hinge margin. 14 distal teeth larger, angular and more oblique to the hinge margin. Proximal posterior teeth short, about 3-5, distal 8 teeth large obliquely set and angulated. The region beneath the umbo is not complete, but there seems to be a flat or slightly concave part just where the two series of tecth mect. The anterior adductor scar is elongate and placed rather low, the posterior adductor scar distinct, ovate and placed below the distal tooth. Pallial line entire. Length 13.2 mm, height 12.6 mm, semidiameter c. 2 mm.