''Cedaria'' is an extinct genus of trilobites from the late

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

. It is a small, rather flat trilobite with an oval outline, a headshield and tailshield of approximately the same size, 7 articulating segments in the middle part of the body and spines at the back edges of the headshield that reach half the length of the body. ''Cedaria'' lived during the early part of the Upper Cambrian ( Dresbachian), and is especially abundant in the Weeks Formation.

Description

''Cedaria'' has an ovate outline of long on average (maximum size 2.5 cm) and ¾ as wide between the tips of the genal spines. The headshield (or

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) is parabolic in shape with a well defined wide, and typically darker colored border of about 10% of the glabellar length or equal to a thorax segment. The well-defined central raised area (or

glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior ...

) tapers slightly forward with a rounded front, but lateral furrows are weakly defined. The backward occipital ring is well defined. The distance from the glabella to the border (or preglabellar field) is approximately one-quarter the length of the glabella or twice the width of the border. The eyes are kidney-shaped, about one-quarter the length of the glabella and at its midlength, and they are positioned close to the glabella, at one-third of its width. The remaining parts of the cephalon, called fixed and free cheeks (or fixigenae and librigenae) are flat. The fracture lines (or sutures) that in moulting separate the librigenae from the fixigenae are divergent just in front of the eyes, becoming parallel near the border furrow and slightly convergent at margin. From the back of the eyes the sutures bends outward and slightly backward, curving backward at the lateral border furrow and cutting the posterior margin in the inner bend of the spine (or opisthoparian sutures). The articulating middle part of the body (or

thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main di ...

) has 7 segments, the outer tips bending backwards, pointed and darker. The tailshield (or

pygidium The pygidium (: pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compos ...

) is semicircular, straight or almost indented and has a long, low, tapering axis with 5 or 6 rings, and 4 or 5 pleural furrows. The border in the pygidium is as wide as in the cephalon and is also often darker, but the border furrow is very shallow or absent.

Taxonomy

''Bonneterrina'', ''Carinamala'', ''Cedaria'', ''Cedarina'', ''Paracedaria'', ''Jimachongia'' and ''Vernaculina'' together comprise the family Cedariidae.

Reassigned species

* ''C. buttsi'' = ?''Crepicephalus'' * ''C. woosteri'' = ?

Distribution

* ''C. minor'' appears in the Upper Cambrian of the United States (between 200 m above the base of the Weeks Formation 15 m into the Big Horse Limestone Member, Orr Formation,

House Range The House Range is a north-south trending mountain range in Millard County, of west-central Utah. The House Range was named in 1859 by James H. Simpson. It was named by Simpson because "...of its well-defined stratification and the resemblan ...

, Millard County, Utah), Canada (Rabbitkettle Formation, Mackenzie Mountains), and Greenland. * ''Cedaria'' is also reported in the Warrior Formation in Pennsylvania.Tasch, Paul, 1951, Fauna and Paleoecology of the Upper Cambrian Warrior Formation of Central Pennsylvania, Journal of Paleontology, Vol. 25, No. 3, pp. 275-306, pls. 44-47, May 195
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References

{{Taxonbar, from=Q15738362 Ptychopariida genera Cambrian trilobites Wheeler Shale Paleozoic life of the Northwest Territories Paleozoic life of Yukon