PBDB Taxon

Basic info	Taxonomic history	Classification	Included Taxa
Morphology	Ecology and taphonomy	External Literature Search	Age range and collections

Eoplectodonta (Eoplectodonta) semirugata

Strophomenata - Strophomenida - Sowerbyellidae

Taxonomy

Plectambonites sericea semirugata was named by Reed (1917) [= Leptaena quinquecostata, M'Coy, Salter 1873. Gat. Camb. Silur. Foss. Woodw. Mus., p. 64]. It is a 3D body fossil.

It was recombined as Eoplectodonta semirugata by Williams (1962); it was recombined as Eoplectodonta (Eoplectodonta) semirugata by Candela and Harper (2014).

Subspecies

Eoplectodonta (Eoplectodonta) semirugata plicata

Sister species lacking formal opinion data

E. estriatacostatus, E. paracostata

Year	Name and author
1917	Plectambonites sericea semirugata Reed pp. 884 - 885 figs. Plate XV, figs. 18-26
1962	Eoplectodonta semirugata Williams pp. 181 - 182 figs. Pl. XVII, figs. 24-27
2014	Eoplectodonta (Eoplectodonta) semirugata Candela and Harper pp. Supplement 1

Diagnosis

Reference	Diagnosis
F. R. C. Reed 1917	Shell transversely semielliptical, plano-convex to concavo-convex, about twice as wide as long ; cardinal angles acutely pointed at about 45°-60°, sometimes slightly produced and subalate; cardinal margin with 6-8 denticulations on each side of beak, decreasing in size to lateral angles. Pedicle-valve gently convex, with lateral portions somewhat flattened ; beak small, pointed, notv projecting, scarcely incurved ; interior with pair of small short pointed subrhomboidal diductors diverging at about 60°-75°, extending about one-fifth to one-fourth the length of the valve, with swollen boss between them ; vascular trunks diverging at about 60°, strong, well marked, deeply sunk, running along diductors, and extending beyond them for about half the length of valve, rarely provided with lateral branches. Brachial valve flat or very slightly concave ; cardinal process tripartite ; interior with large triangular muscle-scar formed by pair of flabelliform contiguous double muscle-scars raised on thickened platform, extending fully half the length of valve and radially ridged. Interiors of both valves covered with radially arranged small pustules becoming larger towards margins. External surface of shell covered with 20-28 strong radii, mostly developed only near margin, with 4 or 5 smaller thread-like lines between them; lateral portions of valves marked with 9-10 more or less wavy concentric wrinkles meeting hinge-line at 45°-60°.
A. Williams 1962	Semicircular, concavo-convex Eoplectodonta with a dominantly convex to subcarinate transverse profile and rarely plicate anteriorly, pedicle valve just over one-half as long as wide; radial ornamentation consisting of differentially thickened parvicostellae with a modal count of 17 per 2 mm. in the median portions of pedicle valves about 5 mm. anterior of the umbones; postero-lateral rugae paired, inclined acutely to the hinge-line and most commonly numbering 8 or more within 5 mm. of the right side of the ventral umbo; denticles, rarely developed along the hinge-lines and exclusively in adult stages of growth; dental lamellae short, ventral muscle-field less than one-sixth as long as the pedicle valve, impressed as a pair of divergent, elliptical scars separated by a median ridge; dorsal septate field variable in length but averaging three-fifths of the length of the brachial valve, median septum developing later than lateral septa but dominant in adult shells.