Biology:Megadictyon

Megadictyon is a genus of Cambrian lobopodian known from the Chengjiang biota of China. It closely resembles Jianshanopodia and Siberion, with which it has often been placed in the family Siberiidae. The name of the genus is occasionally mis-spelt as Magadictyon.

Description

Megadictyon is a large lobopodian, with a body length (excluding appendages) possibly up to 20 centimetres (7.9 in) in total. The head has a pair of robust frontal appendages associated with rows of spines and terminal claws. Located on the underside of the head is a radiodont-like mouthpart formed by multiple layers of plates and tooth-like structures. The trunk is wide and annulated, with a pair of well-developed lobopodous limbs on each body segment. Only 8 segment/limb pairs are countable in the incomplete fossil materials which are lacking the posterior region, so it may have had more (possibly up to 11 to 13) in nature. It also has pairs of digestive glands similar to those of basal arthropods.

Taxonomy and phylogeny

Megadictyon has often been placed in the family Siberiidae along with Jianshanopodia and Siberion, which in turn are thought to represent among the closest relatives of arthropods among lobopodians. Phylogeny of Panarthropoda and lobopodians after Knetcht et al. 2025:

	†Diania 80px
	†Lenisambulatrix 80px         †Paucipodia 80px       †Thanahita 80px     †Eoconchariidae   †Microdictyon 80px     †Fusuchoncharium     †Quadratapora           †Xenusion 80px     †Onychodictyon 80px         †Strictocorniculum     †Rhombocorniculum     †Orstenotubulus80px     †Carbotubulus     †Hallucigenia fortis     †Hallucigenia sparsa 80px       †Hallucigenia hongmeia       †Cardiodictyon 80px       Tardigrada 80px   †Luolishaniida     †Ovatiovermis 60px     †Facivermis 80px         †Luolishania 80px   †Collinsovermidae   †Acincocricus       †Collinsovermis 80px       †Collinsium     †Entothyreos 80px                               †Aysheaiidae   †Aysheaia 80px       †Hadranax 80px     †Palaeocampa 80px       Antennopoda     †Antennacanthopodia 80px     Onychophora (velvet worms) 80px       †Siberiidae   †Siberion 80px     †Megadictyon 80px     †Jianshanopodia 80px           †Pambdelurion 80px     †Kerygmachelidae 80px         †Opabiniidae 80px       †Radiodonta (e.g. Anomalocaris) 80px     Deuteropoda (modern arthropods) 100px

Cladogram after McCall 2023:

Total group Euarthropoda	†Siberiidae   †Siberion 100px     †Megadictyon 100px     †Jianshanopodia 100px       †Kerygmachelidae   †Utahnax 100px       †Kerygmachela 100px     † Mobulavermis 100px             †Omnidens 100px     †Pambdelurion 100px         †Opabiniidae 100px       †Caryosyntrips 100px       †Radiodonta (e.g. Anomalocaris) 100px       Deuteropoda (modern arthropods) 100px

References

Template:Lobopodia Wikidata ☰ Q48968954 entry