Kingdom Animalia Class Trilobita Family Weymouthiidae | Phylum Arthropoda Order Agnostida Rank Genus | |
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Similar Serrodiscus, Eodiscina, Agnostina, Agnostida | ||
Ninadiscus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the Botomian.
Contents
Distribution
Ninadiscus is known from the Lower Cambrian (Botomian) of northwestern Mongolia (Egyngolskaya Suite) and the USA (New York).
Description
Like all Agnostida, Ninadiscus is diminutive and the headshield (or cephalon) and tailshield (or pygidium) are of approximately the same size (or isopygous) and outline. Like all Weymouthiidae, Bolboparia lacks eyes and rupture lines (or sutures). The central raised area of the cephalon (or glabella) is tapering gently forward with a rounded front that touches the furrow that defines the very long anterior border (measured along the axis of the cephalon), that carries three symmetrically arranged tubercles. Border furrow uniform throughout, border narrow at the sides of the cephalon. The most backward part of the glabella (called occipital ring or L0) is short along the axis. The second part from the back (L1) is expanded posterodorsally into a well-rounded protrusion. The furrows S1 and S2 (between L1, L2 and L3) are well impressed. The third part from the back (L2) is shorter than the frontal lobe (L3), which is shorter than L1. Thorax has not yet been found. Pygidium has a long, narrow axis of 10 rings, virtually reaching the posterior border. The pleural areas left and right of the pygidial axis are smooth. The border around the pygidium virtually absent.