| ORDER AGNOSTIDA Suborder Agnostina Superfamily Agnostoidea Superfamily Condylopygoidea Suborder Eodiscina |
Suborder Eodiscina
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Below are some representative Eodiscina:
| Pagetia Eodiscidae  |
Tsunyidiscus Tsunyidiscidae  |
Serrodiscus Weymouthiidae  |
Compare the pictorial approach to the narrative equivalent below (salient features in color):
| Suborder Eodiscina
Introduction: There is some controversy over the placement of Eodiscina in the Agnostida. Presence of eyes, sutures, and typical thoracic structure suggest that Eodiscina are clearly trilobites (perhaps akin to Ptychopariida), and the overall similarity to Agnostina (and placement in Agnostida) prevails in the 1997 systematic treatment of the current Treatise. Cephalon: with proparian sutures, when present; some retain eyes; glabella usually simple, may be narrow and tapering. Thorax: 2 or 3 thoracic segments of normal trilobite form, with articulating half-rings Pygidium: axis can be long and narrow, extending close to margin, generally distinctly divided into more than 3 ringlike segments; pleural region segmented in some species, sometimes pygidial segmentation effaced; border furrows often very deep; axis sometimes spin-bearing. |
