GENUS AMIGDOSCALPELLUM ZEVINA, 1978 B

FIGURES 1A–C, 3E–G, 6A–E, 7U–Y, 8B, F, J, 11A–D, 12Q–T

Type species

Arcoscalpellum manum Zevina, 1973, by subsequent designation Zevina, 1978b.

Diagnosis

Sculpture of strong, radially arranged, rounded raised ridges on all plates except carina; carinolatera articulate across midline by means of zig-zagging, alternating ridges that diverge from umbones. Umbones of carinolatera central to subcentral, close to base of carina, not prominent. Inframedian latus narrow, triangular, more rarely elongate, rectangular, umbo apical, often not extending to top of carinolatus and rostrolatus. Rostrum small, less than half the height of the rostrolatus, narrow, rounded oval rhombic outline.

Included species

Scalpellum vitreum Hoek, 1883, Scalpellum rigidum Aurivillius, 1898, Scalpellum mamillatum Aurivillius, 1898, Arcoscalpellum truncatum Hoek, 1883, Scalpellum elegans Hoek, 1907, Scalpellum formosum Hoek, 1907, Scalpellum trapezoideum Hoek, 1907, Scalpellum semisculptum Pilsbry, 1907, Scalpellum aurivilli Pilsbry, 1907, Scalpellum galapaganum Pilsbry, 1907, Scalpellum rigidum Aurivillius, 1898, Scalpellum sculptum Hoek, 1907, Scalpellum (Arcoscalpellum) constellatum Withers, 1935, Arcoscalpellum pertosum Foster, 1978, Scalpellum (Arcoscalpellum) bellulum Withers, 1935 (Cretaceous, Campanian, UK), and Arcoscalpellum turinensis Withers, 1953 (Miocene, Helvetian, Turin, Italy). Young (2007: 59–60) provided a useful discussion of extant species of Amigdoscalpellum, and suggested that extensive synonymy of taxa was a likely possibility.

Remarks

Thus defined, Amigdaloscalpellum appears to be a monophyletic entity. The distinctive radial sculpture is also present, albeit in a weaker and more restrict- ed form, on some fully grown individuals of a few species of Catherinum (e.g. Ca. australicum, Ca. recurvitergum, and Ca. striolatum; see Young, 1998). These can, however, always be distinguished on the basis of the morphology of the inframedian latus and the overlap of the scutum by the upper latus. Note that the genus as here defined also includes some taxa traditionally referred to Arcoscalpellum (such as Arcoscalpellum truncatum), which fall naturally in Amigdoscalpellum .