Ninadiscus
| Ninadiscus Temporal range:
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| a drawing of Ninadiscus strobulatus, cephalon and pygidium | |
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| Genus: | Ninadiscus Korobov, 1980
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Ninadiscus Korobov, 1980, [1] is a genus of Eodiscinid trilobite belonging to the family Weymouthiidae Kobayashi (1943), [2] Order Agnostida Salter (1864). [3] It lived during the Botomian Stage = late Lower Cambrian Stage 4 (upper of two stages subdividing the un-named Series 2); the upper Botomian boundary corresponds to the base of the Middle Cambrian, the Miaolingian Series and Wuliuan Stage.
Distribution
Ninadiscus is known from the Lower Cambrian (Botomian) of northwestern Mongolia (Egyngolskaya Suite) and the USA (New York). [4]
Description
Like all Weymouthiidae, Ninadiscus lacks eyes and facial sutures, with the glabella tapering gently forward, rounded frontally and extending to the anterior border furrow. The cephalic border is broad frontally (sag.), bears three transversely arranged tubercles and narrows markedly towards posterior. Posterior cephalic margin is straight (tr.) and merely angulate abaxially. The occipital ring (L0) is short (sag). L1 is swollen and well-rounded. Two transglabellar furrows (S1 and S2) are well impressed (maximum cephalic width opposite S1). L2 is shorter than the frontal glabellar lobe (L3). Thorax unknown. The long and narrow pygidial axis is composed of 10 rings and almost reaches the posterior margin. The pleural fields are smooth and the pygidial border is absent except anteriorly. [4]
References
- ^ KOROBOV, M. N. 1980. Biostratigrafiia i miomernye trilobity nizhnego kembriia Mongolii [Biostratigraphy and miomeroid trilobites from the Lower Cambrian of Mongolia]. Joint Sov.-Mongol. Sci.- Res. Geol. Exp., Trans. 26: 5-108 [in Russian].
- ^ KOBAYASHI T. 1943. Brief notes on the Eodiscids 1, their classification with a description of a new species and a new variety. Proceedings of the Imperial Academy, Tokyo, Volume 19, pp. 37 - 42.
- ^ SALTER, J. W. 1864: On some new fossils from the Lingula-flags of Wales. Quarterly Journal of the Geological Society of London, 20, 233–241.
- ^ a b WHITTINGTON, H. B. et al., Part O, Treatise on Invertebrate Paleontology. Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida. 1997
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