Carimersa

Carimersa is an extinct genus of artiopodan arthropod known from the Silurian 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 3 centimetres (1.2 in), with a max width of about 1.25 centimetres (0.49 in). 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, 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 and gastropods 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, more closely related to Aglaspidida, Kodymirus and Eozetetes than to Cheloniellida, Sidneyia or Emeraldella. Cladogram after McCoy et al. 2025: