''Carimersa'' is an extinct genus of

artiopoda Artiopoda is a clade of extinct arthropods that includes trilobites and their close relatives. It was erected by Hou and Bergström in 1997 to encompass a wide diversity of arthropods that would traditionally have been assigned to the Trilobitomor ...

n arthropod known from the

Silurian The Silurian ( ) is a geologic period and system spanning 23.5 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the third and shortest period of t ...

Coalbrookdale Formation of Herefordshire, England.

Description

The body is flattened, and divided into the head with five pairs of paired appendages, the trunk with 10 appendage-bearing segments, a limbless abdomen with 4 segments, with the body terminating with tailspine. The total length of the body excluding the tailspine is around , with a max width of about . The first antennae-like head appendage bears three flagellae-like structures. The second and third head appendages are uniramous and have basipods (basal segments) modified into spined gnathobases (used to process food). The last two head appendages and the trunk limbs are

biramous The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, ...

, and have robust endopods that bear spines, with the exopods being flap-like and reinforced by a rod-like structure.

Ecology

''Carimersa'' was likely an actively swimming organism that probably swam close to the sediment surface. The presence of associated shelly microfossils of

radiolarians The Radiolaria, also called Radiozoa, are unicellular eukaryotes of diameter 0.1–0.2 mm that produce intricate mineral skeletons, typically with a central capsule dividing the cell into the inner and outer portions of endoplasm and ecto ...

and

gastropods Gastropods (), commonly known as slugs and snails, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and from the land. Ther ...

suggests that it may have been a microdurophagous predator, using the spines on its limb endopods to capture prey and move it towards the mouth, where it would be processed by the gnathobases on the second and third head appendages before being ingested.

Taxonomy

''Carimersa'' has been placed as a member of Vicissicaudata within

Artiopoda Artiopoda is a clade of extinct arthropods that includes trilobites and their close relatives. It was erected by Hou and Bergström in 1997 to encompass a wide diversity of arthropods that would traditionally have been assigned to the Trilobitomor ...

, more closely related to Aglaspidida, '' Kodymirus'' and ''

Eozetetes ''Eozetetes'' is a genus of vicissicaudatan artiopod from the Emu Bay Shale of Australia. It contains one species, ''Eozetetes gemmelli''. Description ''Eozetetes'' is roughly 3 cm long, with the tail spine making up half of this. The ce ...

'' than to Cheloniellida, ''

Sidneyia ''Sidneyia'' is an extinct marine arthropod known from fossils found from the Early to the Mid Cambrian of China and the Mid Cambrian Burgess Shale of British Columbia, Canada. Description Sidneyia size comparison.svg, Size comparison of ''Si ...

'' or ''

Emeraldella ''Emeraldella'' is a genus of arthropod known from the Middle Cambrian of North America. The type species ''E. brocki'' was described in 1912 from the Burgess Shale. 21 specimens of ''Emeraldella'' are known from the Greater Phyllopod bed, where th ...

''. Cladogram after McCoy et al. 2025:

References

{{Taxonbar, from=Q121358657 Artiopoda Prehistoric arthropod genera Fossil taxa described in 2023