| Weymouthia Temporal range: | |
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| Llinedrawing of Weymouthia nobilis | |
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| Genus: | Weymouthia Raymond, 1913 |
| Type species | |
| Agnostus nobilis Ford, 1872 | |
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Weymouthia is an extinct genus of eodiscinid agnostid trilobites, which lived at the end of the Lower Cambrian, in what are now the eastern United States, England, Siberia and China.
Like all Agnostida, Weymouthia is diminutive and the headshield (or cephalon) and tailshield (or pygidium) are of approximately the same size (or isopygous) and outline. Like all Weymouthiidae, Weymouthia lacks eyes and rupture lines (or sutures). The headshield (or cephalon) is approximately as long as wide, lacks facial sutures and is eyeless. The tailshield (or pygidium) is about 1.2× as wide as long. Both are effaced except for a furrow close to their borders. The cephalic border bears lateral tubercles. The thorax consists of three segments. [1]
Weymouthia is named after Weymouth, Massachusetts. [2]
Fletcher & Theokritoff (2008) [4] designated Shaw's (1950, pl. 79, fig. 24) [5] specimen of “ Weymouthia nobilis (Ford, 1872)” [6] as the holotype of a new species, Serrodiscus weymouthioides, and considered Runcinodiscus Rushton (in Bassett et al., 1976) [7] [= ?Weymouthia nobilis (Ford, 1872)] to be a junior synonym of Serrodiscus; Rushton (1976) had previously regarded Weymouthia and Runcinodiscus as closely allied with Serrodiscus. Weymouthia nobilis (Ford 1872), first described from the Taconic region of New York State, is also recorded from the Protolenus Limestone (Ac5) [Protolenid-Strenuellid Zone] at Comley, Shropshire, England (Cobbold 1931), [8] but Rushton (in Bassett et al., 1976, p. 637) showed that the English specimens are specifically distinct from W. nobilis as described by Ford (1872), and thus erected his new genus and species, Runcinodiscus index Rushton (in Bassett et al. 1976, p. 636-7).
Redlichiida is an order of trilobites, a group of extinct marine arthropods. Species assigned to the order Redlichiida are among the first trilobites to appear in the fossil record, about halfway during the Lower Cambrian. Due to the difficulty to relate sediments in different areas, there remains some discussion, but among the earliest are Fallotaspis, and Lemdadella, both belonging to this order. The first representatives of the orders Corynexochida and Ptychopariida also appear very early on and may prove to be even earlier than any redlichiid species. In terms of anatomical comparison, the earliest redlichiid species are probably ancestral to all other trilobite orders and share many primitive characters. The last redlichiid trilobites died out before the end of the Middle Cambrian.
Agnostus, is a genus of agnostid trilobite belonging to the Family Agnostidae, that lived during the late Middle Cambrian – early Upper Cambrian. It is the type genus of the family Agnostidae and is subdivided into two subgenera, Agnostus and Homagnostus.
The Paradoxididae are a family of trilobites, a group of extinct marine arthropods. They occurred during the late Lower Cambrian (Toyonian) and disappeared at the end of the Middle Cambrian. Representatives of this family have been found in the paleocontinents of Avalonia, Baltica, and Gondwana, now Canada, USA, England, Wales, Morocco, Spain, Czech Republic, Poland, Russia, Mongolia, and Turkey. Species in this family can typically grow large to very large, are relatively flat, have an inverted egg-shaped outline, opisthoparian sutures, a glabella that in early genera has parallel sides and expands forward in later representatives, and approaches or reaches the frontal border. All species have an almost semicircular headshield with long backward-directed genal spines. The articulate middle part of the body consists of 15 to 21 segments ending in sickle-shaped spines that to the back curve increasingly further backwards. The tailshield is small.
Acimetopus Rasetti, 1966, is a genus of Eodiscinid trilobite belonging to the family Weymouthiidae Kobayashi (1943), Order Agnostida Salter (1864). It lived during the Botomian stage. = late Lower Cambrian Stage 4 ; the upper Botomian boundary corresponds to base of the Middle Cambrian, Miaolingian Series and Wuliuan stage.
Analox Rasetti, 1966 is a genus of Eodiscinid trilobites belonging to the family Weymouthiidae Kobayashi T. (1943), Order Agnostida 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.
Bolboparia is an extinct genus of eodiscinid agnostid trilobites. It lived during the late Lower Cambrian in what today Canada and the United States.
Oodiscus is an extinct genus of small size trilobite, with three known species. It lived during the Toyonian in 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.
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.
Resserops is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the middle of the Atdabanian or the early part of the Botomian stage, which lasted from approximately 524 to 518.5 million years ago. This faunal stage was part of the Cambrian Period. It has been found in Spain and southern Morocco. It can be recognised by the sabre-like spines of the headshield that are a smooth continuation of the frontal edge, and the enlarged spines on the 9th segment of the thorax.
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.
Runcinodiscus Rushton is a genus of Lower Cambrian Eodiscinid trilobite belonging to the family Weymouthiidae, Order Agnostida.
Acmarhachis is a genus of trilobite in the order Agnostida, which lived in what are now Australia, Canada, China (Anhui), Kazakhstan, Russia (Kharaulakh), and the US. It was described by Resser in 1938, and the type species is Acmarhachis typicalis.
Litometopus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the Botomian stage.
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.
Toragnostus is a genus of trilobites restricted to the late Middle Cambrian. 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.
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.
Anabaraspis is a genus of redlichiid trilobite. A. splendens occurs in the uppermost Lower Cambrian and lowest Middle Cambrian of Russia. In Anabaraspis there is a long area in front of the glabella which is not differentiated in a border and a preglabellar field. This is a unique character in the family Paradoxididae. The frontal lobe of the central raised area of the headshield is slightly pointed, rather than rounded or truncate, a character shared with Plutonides, though, in Plutonides it hangs over the short anterior border.
Serrodiscus Richter and Richter 1941. is a genus of Eodiscinid trilobite belonging to the family Weymouthiidae Kobayashi T. (1943), Order Agnostida. It lived during the late Lower Cambrian, with remains found in Canada, China (Gansu), The United Kingdom (England), Germany (Silesia), Poland, the Russian Federation, and the United States. It is named for the spines on the ventral side of the pygidium, which give it a serrated impression.
The Paradoxidoidea Hawle & Corda 1847, are a superfamily of trilobites, a group of extinct marine arthropods. They occurred during the late Lower Cambrian (Toyonian) and disappeared at the end of the Middle Cambrian.
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