Artiopoda Temporal range:
Misszhouia, a nektaspid
Cheloniellon, a cheloniellid
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
(unranked):	†Artiopoda Hou and Bergstrom, 1997
Subgroupings
†Squamacula †Thulaspis Protosutura †Acanthomeridion †Zhiwenia †Australimicola †Campanamuta †Falcatamacaris †Molaria †Retifacies †Pygmaclypeatus †Bailongia †Strabopida? Trilobitomorpha †Retifacies? †Pygmaclypeatus? †Campanamuta? †Kwanyinaspis †Arthroaspis †Tonglaiia[1] †Nektaspida †Trilobita †Agnostida(Traditionally included within Trilobita) †Conciliterga †Haifengella †Helmetia †Kuamaia †Kwanyinaspis †Rhombicalvaria †Saperion †Skioldia †Tegopelte †Xandarellida (=Petalopleura) †Luohuilinella †Cindarella †Phytophilaspis †Xandarella †Sinoburius †Zhugeia[1] Vicissicaudata †Xenopoda (possibly paraphyletic) †Sidneyia †Emeraldella †Etania †Kodymirus †Eozetetes †Carimersa †Cheloniellida †Aglaspidida

The Artiopoda is a grouping of extinct arthropods that includes trilobites and their close relatives. It was erected by Hou and Bergström in 1997^[2] to encompass a wide diversity of arthropods that would traditionally have been assigned to the Trilobitomorpha. Trilobites, in part due to their mineralising exoskeletons, are by far the most diverse and long lived members of the clade, with most records of other members, which lack mineralised exoskeletons, being from Cambrian deposits.^[3]

Description

Morphology of Cambrian artiopod Retifacies, showing the morphology of the limbs (E, F) Key for limb morphology: exopod (exo) exite (exi) protopodite (pt) podomere (pd) spine/setae (s) terminal claw (tc)

According to Stein and Selden (2012) artiopods are recognised by the possession of filiform antennulae, limbs with bilobate exopods, with the proximal lobe being elongate and bearing a lamella, while the distal lobe is paddle-shaped and setiforous (bearing hair-or bristle like structures). The limb endopod has seven podomeres/segments, with first four podomeres bearing inward facing (endite) structures, while podomeres five and six are stenopodous (cylindrical and stout). Common plesiomorphies also include the antellules and at least three sets of post-antellulae limbs being incorporated into the head shield, the postantennular limbs having no or little differentiation into distinct morphologies, and broad paratergal folds which contribute to the dorsoventrally flattened look of artiopods.^[4] The limbs of artiopods have also been suggested to bear exites, which were described as similar those of the megacheiran Leanchoilia and probably not homologous to those present in crustaceans.^[5]

Taxonomy

Gallery

Phylogeny

After Jiao et al. 2021.^[11]

References