''Primoriella'' 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 ...

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

, an extinct group of marine

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

s. The only known species, ''P. bella'' occurs in the uppermost Lower Cambrian of Russia (''Redlichina culmenica'' beds, far eastern Siberia). It is related to ''

Paradoxides ''Paradoxides'' is a genus of large to very large trilobite found throughout the world during the Middle Cambrian period. One record-breaking specimen of ''Paradoxides davidis'', described by John William Salter in 1863,Salter, J. W. 1863. "On t ...

'', but can be distinguished from it by only slightly forward expansion of the (

glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior ...

) a character shared with '' Anabaraceps'' and '' Schagonaria''. In ''Primoriella'' however, the front of the glabella touches the roll-like border, causing it to slightly bulge forward, while in ''Anabaraceps'' there is a roll-like preglabellar field as wide as the flat border in front of it. The glabella of ''Primordiella'' is less than twice as long as wide, and differs from ''Schagonaria'' in which it is more than twice as long as wide. The

thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main di ...

and

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 ...

are not known.

References

Cambrian trilobites Paradoxidoidea Fossils of Russia Fossil taxa described in 1973 {{redlichiida-stub