Amydroptychus markowitzi, Feldman & Schemm-Gregory & Ahmad & Wilson, 2012

Feldman, Howard R., Schemm-Gregory, Mena, Ahmad, Fayez & Wilson, Mark A., 2012, Jurassic rhynchonellide brachiopods from the Jordan Valley, Acta Palaeontologica Polonica 57 (1), pp. 191-204 : 201

Amydroptychus markowitzi sp. nov.

Fig. 3G.

Etymology: Named in memory of Alfred Markowitz (1926–2000), scientist, Renaissance Man, and healer.

Holotype: AMNH FI−72405 .

Type locality: Arda section, Wadi Zarqa, Jordan.

Type horizon: Bed 27, Mughanniyya Formation (Callovian, upper Middle Jurassic).

Material.— Two articulated specimens: AMNH FI−72405 (holotype), AMNH FI−72406 , bed 27, Mughanniyya Formation ( Callovian , upper Middle Jurassic); Arda section, Jordan. Diagnosis.— Amydroptychus with subcircular outline, equibiconvex, medium to large foramen, and rectimarginate anterior commissure with no indication of fold or sulcus .

Description.—Medium−sized shells ( Table 7), outline subcircular and equibiconvex in longitudinal section without any indication of fold or sulcus. Ventral valve covered by 20 simple costae, dorsal valve by 21 costae. Furrows and costae are angular to rounded in cross section. Equibiconvex, apical angle acute, deltidial plates obscured, foramen medium, tubular. Anterior commissure rectimarginate; lateral commissure straight. Ventral beak erect in adults but suberect in juveniles. Twenty−one angular costae on adults and 25 on juveniles. Intercalations and bifurcations observed on juveniles but rare on adult specimens.

The ventral valve is convex in lateral profile with the apex of the convexity occurring at one−third the distance from the beak; in anterior profile the valve is more sharply domed with the flanks sloping somewhat steeply until the commissure is reached.

The dorsal valve is convex in lateral view bulging more posteriorly and sloping gently toward the anterior commissure. In the juvenile specimens the bulge is less developed.

The internal structures of the shells are unknown due to a lack of sufficient material for serial sectioning.

Discussion.—The gentle folding that Cooper (1989) noted as being a conspicuous feature of Amydroptychus formosus is absent here. These specimens resemble Strongyloria circularis Cooper, 1989 but are less globose, lack an arcuately uniplicate anterior commissure, and have a narrower beak. In addition, these shells are more triangular than circular in outline as are Strongyloria circularis and S. subelliptica Cooper, 1989 . Hegab (2005) described Amydroptychus galaensis from the Jurassic of the western side of the Gulf of Suez, Egypt, that differs from the Jordanian shells in their slightly sulcate anterior commissure (2005: 740, figs. 3, 6) and smaller number of costae (16).

Stratigraphic and geographic range.—Callovian; Jordan.