Cerninella aryana, 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 : 553-554

Cerninella aryana sp. nov. Williams, Vannier, and Meidla

Fig. 3A, B, D–F.

Derivation of the name: After the name “ Iran ”, which in its oldest form means the “land of the Aryans”.

Holotype: NMW2004.22 .G.300, a complete heteromorphic left valve.

Type locality: Dahaneh Kolut, east central Iran.

Type horizon: Shirgesht Formation, Section B, lithological Unit B5, sample B−D/3, probably late Middle Ordovician.

Material.—Over one hundred specimens in the NMW collection (NMW.2004.22.G.300, NMW.2004.22.G.329–332, NMW.2004.22.G.380, and many others) from samples B−D/3 and B−D/4. Specimens we have examined range from 0.8 to 1.8 mm in length, probably representing several instars.

Diagnosis.— Cerninella species in which the dorsal termination of the anterior lobe (L1) forms a posterior directed hook shape as it overreaches the dorsum. C. aryana is similar to C. arcadelti Vannier, 1986b , with which it shares narrow lobes, weakly sinusoidal posterior lobes (L3, L4) that overreach the dorsal margin, a short and straight preadductorial lobe (L2), and a similar length to height ratio (1.4 to 1.8), but it differs in the unique morphology of its anterior lobe. C. aryana is much smaller than the type species, C. bohemica , which is over 3 mm in length.

Description.—Weakly preplete, quadrilobate valves. Length to height ratio ranges from 1.4 to 1.8 in the specimens we have measured. Dimorphism is subtle, but heteromorphs appear to have valves that are much higher relative to their length (see Fig. 3F). Lobes are very narrow and are typically of even width throughout, and are separated by broad, well−developed sulci. All lobes are already well developed in small juveniles less than 1 mm in length. Anterior lobe (L1) and third and fourth lobes from anterior (L3, L4), overreach the dorsal margin in adults. Dorsal termination of L1 forms a posterior directed “hook shape” which overreaches the dorsal margin. L3 and posterior−most lobe (L4) weakly sinusoidal. Second lobe from anterior (L2) short, about 3/4 the length of the other lobes. Lobes join ventrally to form a connecting ridge. L4 sometimes divides into two sub−lobes as it approaches the dorsal margin. In adults the velum is well developed, flange like and entire between cardinal corners.

Discussion.—This is the most common palaeocope ostracod in the material we have examined from the Shirgesht Formation. Subtle variation in the length to height ratio of heteromorphs and tecnomorphs of Cerninella was also noted by Vannier (1986b: pl. 8: 3, 4)