Ordovizona amyitisae, Pour & Williams & Vannier & Meidla & Popov, 2006

Pour, Mansoureh Ghobadi, Williams, Mark, Vannier, Jean, Meidla, Tõnu & Popov, Leonid E., 2006, Ordovician ostracods from east central Iran, Acta Palaeontologica Polonica 51 (3), pp. 551-560 : 556

Ordovizona amyitisae sp. nov. Williams, Vannier, and Meidla

Fig. 3M–O.

Derivation of the name: Amyitis, granddaughter of the king of Media and wife of Nebuchadnezzar the great king of Babylonia. Later legend credited Nebuchadnezzar with building the Hanging Gardens of Babylon, for his wife Amyitis.

Holotype: NMW2004.22 G.302, a complete left valve.

Type locality: Dahaneh Kolut, east central Iran.

Type horizon: Shirgesht Formation, Section B, lithological Unit B5, sample B−D/4, probably late Middle Ordovician.

Material.— Nine specimens ( NMW2004.22 G.302–310) from sample B−D/4. The largest specimen in our collection is 1.7 mm long .

Diagnosis.—Species of Ordovizona , adults typically greater than 1.5 mm long, with a broad velar ridge (200 µm wide), which is of even width except where it narrows at the cardinal corners. Or. amyitisae differs from the type species Or. sulcata and from Or. longa Schallreuter, 1983 by its broader velar ridge, and by its larger size (about 1/3 rd greater in length than the other two species). It differs from Or. immanis Becker, 1994 (length up to 0.68 mm) by its larger size, broader velar ridge and lack of the bow shaped dorsal plica that characterizes that species.

Description.—Valves amplete to weakly preplete. The length to height ratio of the valves we have measured ranges from 1.4 to 1.6. Well−developed adductorial pit, traced to the dorsal margin by a shallow sulcament where it meets the narrow dorsal plica. Adductorial pit demarcates broadly convex anterior and posterior lobal surfaces. Lateral surface has strong horizontal striae that are joined vertically by reticulae. Velum entire between the cardinal corners, maximum width ventrally (200 µm), narrowing as it approaches the dorsal margin both anteriorly and posteriorly.

Discussion.—We follow Becker (1997, 2002) in considering Ordovizona and the Ordovizonidae to be presumed palaeocopes.

The reticulae between the lateral ridges on the surface of Or. amyitisae are very coarsely preserved when compared to the well−preserved material of Ordovizona described by Schallreuter (1969, 1983).

Ordovizona is also known from the Precordillera of Argentina (Maria J. Salas, personal communication 2003). This indicates that the genus had wide dispersal between Baltica, Gondwana, and other palaeocontinental entities by the late Middle Ordovician.