The Hebediscidae Kobayashi, 1944, are a family of trilobites belonging to the order Agnostida that lived during the Lower Cambrian (Atdabanian to Toyonian). They are small or very small, and have a thorax of two or three segments. The Hebediscidae include five genera (see box).
| Hebediscidae Temporal range:
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| Tchernyshevioides ninae | |
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| Superfamily: | Eodiscoidea
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| Family: | Hebediscidae Kobayashi, 1944
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Delgadoiinae, Pagetiellinae, Dicerodiscinae | |
Taxonomy edit
The Hebediscidae probably descended from the Tsunydiscidae and gave rise to the Weymouthiidae.[2]
Description edit
Like all Agnostida, the Hebediscidae are diminutive and the headshield (or cephalon) and tailshield (or pygidium) are of approximately the same size (or isopygous) and outline. In the Hebediscidae, the central raised area of the cephalon (or glabella) is wide at its rear end, has parallel sides or tapers forward, and without transverse glabellar furrows, although the lobes may be apparent if they are expanded. A three segment thorax is known in Hebediscus, Delgadella and Tchernyshevioides. The pygidium has a wide, tapering axis of more than four segments.[1]
References edit
- ^ a b WHITTINGTON, H. B. (1997). Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida. Treatise on Invertebrate Paleontology. Vol. Part O, Revised. pp. 390–392.
- ^ JELL, P. A. (1975). "Australian Middle Cambrian Eodiscoids with a review of the superfamily". Palaeontographica Abteilung A. 150: 1–97. cited in WHITTINGTON, H. B. (1997). Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida. Treatise on Invertebrate Paleontology. Vol. Part O, Revised. pp. 348–349.
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