Litometopus

Litometopus
Temporal range: Botomian (Olenellus-zone)
Litometopus longispinus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Trilobita
Order: Agnostida
Family: Weymouthiidae
Genus: Litometopus
Rasetti, 1966
species
  • L. longispinus Rasetti, 1966[1]

Litometopus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the Botomian stage.[2]

Taxonomy

Litometopus may be a synonym of Cobboldites.[3]

Distribution

Litometopus is known from the upper Lower Cambrian of the United States (Acimetopus bilobatus faunule, Taconic, Griswold Farm, New York).[3]

Description

Like all Agnostida, Litometopus 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 is almost semicircular. The central raised area of the cephalon (or glabella) has a furrow along its outline, but no furrows are crossing it. It tapers forward and touches the border furrow. The border is convex, and it carries pair of small marginal spines at approximately ⅓ of the cephalic length from the front, and large genal spines, that are directed backwards and slightly outwards (±15°). Pygidium is the same shape as the cephalon. The pygidial axis is tapering backwards and touches the border furrow. It has a furrow along its outline, but crossing furrows are very faint or indiscernible. The border is flat and wide, and its doublure is sloping adaxially, and with serrated margin.[3]

References

  1. ↑ Rasetti, Franco (1966). "New Lower Cambrian trilobite faunule from the Taconic sequence of New York". Smithsonian Miscellaneous Collections. 148 (9): 1–52.
  2. ↑ Sepkoski, Jack (2002). "A compendium of fossil marine animal genera (Trilobita entry)". Bulletins of American Paleontology. 364: 560. Archived from the original on 5 September 2006. Retrieved 12 January 2008.
  3. 1 2 3 Whittington, H. B. et al. Part O, Treatise on Invertebrate Paleontology. Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida. 1997
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