Oodiscus

Oodiscus; Temporal range:
	a drawing of Oodiscus subgranulatus, cephalon and pygidium
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Trilobita
Order:	Agnostida
Family:	Weymouthiidae
Genus:	Oodiscus; Rasetti, 1966
species
	O. subgranulatus Rasetti, 1966 (Type)[1]; O. binodosus Rasetti, 1966; O. longifrons Rasetti, 1966[2][3];

Oodiscus is an extinct genus of small size (about 2 centimetres (0.79 in)) trilobite, with three known species. It lived during the Toyonian in what are now Canada and the USA.

Distribution

O. subgranulatus is known from the upper Lower Cambrian of the USA (New York, Griswold Farm) and Canada (Newfoundland).

Ecology

Oodiscus occurs in association with other Weymouthiidae (Acidiscus, Acimetopus, Analox, Bathydiscus, Bolboparia, Leptochilodiscus, Serrodiscus), and Calodiscus.[1]

Description

Like all Agnostida, Oodiscus is diminutive and the headshield (or cephalon) and tailshield (or pygidium) are of approximately the same size (or isopygous) and outline. Like all Weymouthiidae, it lacks eyes and rupture lines (or sutures). The cephalon tends towards a rounded square outline. The central raised area of the cephalon (or glabella) is wide (one-third cephalic width), strongly convex, completely unfurrowed except for shallow lateral depressions much to the back. The glabella almost reaches the border. The border has one or two pairs of marginal spines laterally and a pair of small spines posteriorly. One species has a pair of tubercles to the front. The pygidium axis is tapered, does not have furrows, and does not reach the posterior border. The border is virtually flat.[1]

References

Whittington, H. B. et al. Part O, Treatise on Invertebrate Paleontology. Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida. 1997
Global Names Index. "Oodiscus". Retrieved 22 January 2012.
Rasetti, Franco (1966). "New Lower Cambrian trilobite faunule from the Taconic sequence of New York". Smithsonian Miscellaneous Collections. 148 (9): 1–52.

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[Treatise-1] Whittington, H. B. et al. Part O, Treatise on Invertebrate Paleontology. Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida. 1997

[2] Global Names Index. "Oodiscus". Retrieved 22 January 2012.

[Rasetti-3] Rasetti, Franco (1966). "New Lower Cambrian trilobite faunule from the Taconic sequence of New York". Smithsonian Miscellaneous Collections. 148 (9): 1–52.