| Litometopus | |
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| Litometopus longispinus | |
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| Genus: | Litometopus Rasetti, 1966 |
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Litometopus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the Botomian stage. [2]
Litometopus may be a synonym of Cobboldites . [3]
Litometopus is known from the upper Lower Cambrian of the United States ( Acimetopus bilobatus faunule, Taconic, Griswold Farm, New York). [3]
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]
Acidiscus is an extinct genus of eodiscinid agnostid trilobites. It lived during the Botomian stage of the Cambrian period.
Acimetopus is a genus of trilobites that lived during the Botomian stage.
Analox is an extinct genus of agnostid trilobite. It lived during the Botomian stage. It can easily be distinguished from other trilobites by the two furrows that extend forwards and sidewards from the front of the glabella.
Ninadiscus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the Botomian.
Oodiscus is an extinct genus of small size trilobite, with three known species. It lived during the Toyonian it what are now Canada and the USA.
Meniscuchus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the Botomian stage, which lasted from approximately 522 to 516 million years ago. This faunal stage was part of the Cambrian Period. Meniscuchus has been found in the USA, Canada, Russia and Australia.
Parapagetia is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the Botomian stage, which lasted from approximately 524 to 518.5 million years ago. This faunal stage was part of the Cambrian Period.
Dicerodiscus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the early part of the Botomian stage, in China. Four species have been assigned to it. Dicerodiscus is unique for an eodiscoid in having conspicuous and curved spines that are attached anteriorly, and at their base are directed outward perpendicular to the midline, before gradually bending further backwards.
Semadiscus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It has been collected from the Lower Cambrian of Canada (Newfoundland), Russia, and the United States. Only the headshield is known, and it may well be that it would be better to include it in Serrodiscus.
Cirquella is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the Atdabanian stage, in the former continent Laurentia.
Pagetia is a genus of very small, agnostid trilobites, assigned to the family Eodiscidae, and that had a global distribution during the Middle Cambrian. The genus contains 55 currently recognized species, each with a limited spatial and temporal distribution.
Marocconus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It is still debated if it lived at the very end of the Lower Cambrian or at the very beginning of the Middle Cambrian. Marocconus notabilis is the only known species in this genus.
Mallagnostus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the upper Lower Cambrian, with remains found in USA, Canada (Newfoundland), Spain, England, Russia, Mongolia, and the lower Middle Cambrian according to fossils from China and Russia (Yakutia).
Geragnostus is a genus of very small agnostid trilobites whose fossils are found Ordovician-aged marine strata from Eurasia, North America and Argentina.
Eodiscidae is a family of agnostid trilobites that lived during the final Lower Cambrian and the Middle Cambrian. They are small or very small, and have a thorax of two or three segments. Eodiscidae includes nine genera.
The Hebediscidae are a family of trilobites belonging to the order Agnostida that lived during the Lower Cambrian. They are small or very small, and have a thorax of two or three segments. The Hebediscidae include five genera.
The Calodiscidae are a family of trilobites belonging to the order Agnostida that lived during the Lower Cambrian. They are small or very small, and have a thorax of two or three segments. The Hebediscidae include five genera.
Jinghediscus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the lover Middle Cambrian, with remains found in China (Xinjiang) and Australia (Queensland).
Cedaria 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 halflength of the body. Cedaria lived during the early part of the Upper Cambrian (Dresbachian), and is especially abundant in the Weeks Formation.
Serrodiscus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It has been collected from the Lower Cambrian of Canada, Germany (Silesia), Poland, Russia, the United Kingdom (Wales) and the United States. It is named for the spines on the ventral side of the tailshield (or pygidium, which give it a serrated impression.
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