Hebediscidae

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Hebediscidae
Temporal range: Lower Cambrian
Tchernyshevioides drawing white.png
Tchernyshevioides ninae
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Trilobita
Order: Agnostida
Suborder: Eodiscina
Superfamily: Eodiscoidea
Family: Hebediscidae
Kobayashi, 1944
genera
Synonyms

Delgadoiinae, Pagetiellinae, Dicerodiscinae

The Hebediscidae 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).

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]

  1. ^ a b Whittington, H. B. (1997). Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida. Treatise on Invertebrate Paleontology. Part O, Revised. pp. 390–392. 
  2. ^ 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. Part O, Revised. pp. 348–349.