''Toragnostus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

trilobites Trilobites (; meaning "three-lobed entities") are extinct marine arthropods that form the class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most successful of all early animals, ...

restricted to the late Middle

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 ...

. Its remains have been found in the United States, Greenland, Denmark, China, Sweden, the Russian Federation, and Kazakhstan. Its headshield and tailshield are almost completely effaced and it has two thorax segments.

Distribution

* ''T. bituberculatus'' occurs in the late Middle Cambrian of the United States (Hillard Peak area, Alaska) Greenland (''Lejopyge laevigata''-zone, Holm Dal Formation, West Peary-land), Denmark, China (Hunan), Sweden (''Jincella brachymetopa''-zone,

Andrarum Andrarum is a locality situated in Tomelilla Municipality, Skåne County, Sweden. Christinehof Castle is located in Andrarum. Andrarum Church was built in the 12th century and heavily rebuilt in the 18th century. It contains Baroque furnishings, ...

, Skåne), the Russian Federation (''C. oriens'' and ''A. henrici''-zones, Siberian Platform, and

Bennett Island Bennett Island (; ) is the largest of the De Long Islands in the northern part of the East Siberian Sea in North Asia. The area of this island is approximately and it has a tombolo at its eastern end. The highest point of the island is high Mo ...

), and Kazakhstan (

Mayan Mayan most commonly refers to: * Maya peoples, various indigenous peoples of Mesoamerica and northern Central America * Maya civilization, pre-Columbian culture of Mesoamerica and northern Central America * Mayan languages, language family spoken ...

Tian Shan The Tian Shan, also known as the Tengri Tagh or Tengir-Too, meaning the "Mountains of God/Heaven", is a large system of mountain ranges in Central Asia. The highest peak is Jengish Chokusu at high and located in Kyrgyzstan. Its lowest point is ...

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

Description

Like all Agnostida, ''Toragnostus'' is diminutive, with the headshield (or

cephalon Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino Jr., Frank Baldino, Jr., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont ...

) and 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 ...

) of approximately the same size (or isopygous) and outline. Like all Agnostina, ''Toragnostus'' has only two thorax segments. The cephalon and pygidium are almost completely effaced, lacking a cephalic border and with wide pygidial border. The cephalon is strongly convex. The central raised area of the cephalon (or glabella) is outlined at the rear, narrow and tapering forward. It carries an elongated median node, clearly in the front half of the cephalon. The pygidial axis (or rhachis) is very broad, with the frontal lobe (M1) defined by a furrow crossing the axis. There is a weak elongated node on the rhachis.

References

Agnostida genera Agnostoidea Cambrian trilobites Fossils of the United States Fossils of Greenland Fossils of Denmark Fossils of China Fossils of Sweden Fossils of Russia Fossils of Kazakhstan {{agnostida-stub