''Mallagnostus'' Howell, 1935, is a trilobite genus belonging to the family

Weymouthiidae The Weymouthiidae Kobayashi 1943 are an extinct family of eodiscinid agnostid trilobites. They lived during the late Lower Cambrian and earliest Middle Cambrian (Botomian to Delamaran) in the so-called ''Olenellus''- and ''Eokochaspis''-zon ...

Kobayashi T. (1943), Order Agnostida Salter (1864) according to Whittington ''et al''. 1997. It lived during the late Lower Cambrian, with remains found in USA (New York), Canada (Newfoundland), Spain, England, Russia (Tuva, Gorno-Altayskaya), Mongolia, and the early Middle Cambrian as reported from China (Tian Shan) and Russia (Yakutia).

Taxonomy

''Mallagnostus'' was originally described as belonging to the Agnostina, but it is more appropriately placed in the Eodiscina. Within the

, ''Mallagnostus'' belongs to a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

that further includes ''

Tannudiscus ''Tannudiscus'' Pokrovskaya (1959) is a genus of Eodiscinid trilobites belonging to the family Weymouthiidae Kobayashi T. (1943), Order Agnostida (Salter 1864). It lived during the late Lower Cambrian, with remains found in Canada (Newfoundland), ...

'', '' Jinghediscus'' and the Agnostina.

Distribution

* ''M. desideratus'' Walcott, 1890, is from the Lower Cambrian ''Olenellus'' Zone of North America. * ''M. limbatus'' Pokrovskaya, 1959, has been collected from the upper Lower Cambrian of New York, WHITTINGTON, H. B. ''et al''. Part O, ''Treatise on Invertebrate Paleontology.'' Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida. 1997 and the Toyonian of the Russian Federation (Obruchev stage, Shivelig Formation, Shivelig-Khem River, Tuva, Altay-Sayan, Siberia, 51.4° N, 94.2° E) ''cited in'' * ''M. llarenai'' Richter and Richter, 1941, RICHTER, R., & RICHTER, E., 1941. Die Fauna des Unter-Kambriums von Cala in Andalusien. ''Abhandlungen der senckenbergischen naturforschenden Gesellschaft'', 455: 90 pp., 83 figs., 4 pls., Frankfurt. is found in the late Lower Cambrian of Spain (''serratus'' Band, Herrerias-Mergel Formation, Cala).

Ecology

''M. limbatus'' occurs with ''Tannudiscus tannuolaicus'', ''Menneraspis striata'', ''Beldirella pulchra'' and ''Cheiruroides maslovi''.

Description

''Mallagnostus'' is isopygous and, like all Weymouthiidae, lacks eyes and facial sutures. The cephalon is semi-elliptical with unfurrowed glabella (in one species there are lateral indentations). The glabella does not quite reach the broad border furrow. The occipital ring (L0) is short (sag.), ill-defined, and does not carry a spine. Anterior border of cephalon is long, only gently convex, and becomes shallower further from the axis. The border furrow runs into the margin just in front of the genal angle. Thorax of three segments, as in all other Weymouthiidae where the thorax is known. The pygidial axis is conical with at least eight rings, and does not extend to the posterior border furrow. Pleural fields smooth.

References

{{Taxonbar, from=Q6744034 Weymouthiidae Agnostida genera Cambrian trilobites Cambrian trilobites of Europe Cambrian genus extinctions