Phalagnostus

Phalagnostus is a genus of small trilobites, in the order Agnostida. It lived during the Middle Cambrian, in what are now Canada, China, the Czech Republic, Denmark, England, France, the Russian Federation, Wales, Sweden, and possibly the United States. The headshield is almost entirely effaced and wider than the tailshield. The pygidium is also very effaced, but the ovate pygidial axis is well defined and a border furrow is also present.

Taxonomy

Phalagnostus nudus, the type species, was originally described as a species of Battus by Beyrich in 1845, but that name had already been used for a butterfly, and the trilobite genus was also deemed polyphyletic.
Due to the high level of effacement, establishing the relationship of Phalagnostus to other Agnostoidea is difficult. The Treatise lists Phalagnostus as family unknown.

Species previously assigned to ''Phalagnostus''

P. bituberculata = ''Toragnostus bituberculatus''

Distribution

P. nudus is known from the Middle Cambrian of the Czech Republic.P. carinatus has been collected from the Middle Cambrian of China.P. cuneatus was found in the Middle Cambrian of the Russian Federation.P. rasettii and P. shergoldi have been described from the Upper Cambrian of Canada.

Description

This agnostoid is strongly effaced. The cephalon lacks a border furrow. The glabella and small basal lobes are weakly defined. The rhachis is circular to ovate, clearly defined by deep axial furrows. An elongate axial node may be discerned. The pygidium has a narrow border defined by a furrow.