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Megadictyon

Extinct genus of Cambrian lobopodian

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Source updated July 19, 2026

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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.

01Description

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.

02Taxonomy 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

†Lenisambulatrix

†Paucipodia

†Thanahita

†Eoconchariidae

	†Microdictyon

	†Fusuchoncharium

	†Quadratapora

	†Xenusion

	†Onychodictyon

†Strictocorniculum

†Rhombocorniculum

†Orstenotubulus

†Carbotubulus

†Hallucigenia fortis

†Hallucigenia sparsa

†Hallucigenia hongmeia

†Cardiodictyon

Tardigrada

†Luolishaniida

	†Ovatiovermis

	†Facivermis

†Luolishania

†Collinsovermidae

†Acincocricus

†Collinsovermis

	†Collinsium

	†Entothyreos

†Aysheaiidae

†Aysheaia

	†Hadranax

	†Palaeocampa

Antennopoda

	†Antennacanthopodia

	Onychophora (velvet worms)

†Siberiidae

	†Siberion

	†Megadictyon

	†Jianshanopodia

	†Pambdelurion

	†Kerygmachelidae

†Opabiniidae

	†Radiodonta (e.g. Anomalocaris)

	Deuteropoda (modern arthropods)

Cladogram after McCall 2023:

Total group Euarthropoda

†Siberiidae

	†Siberion

	†Megadictyon

	†Jianshanopodia

†Kerygmachelidae

†Utahnax

	†Kerygmachela

	† Mobulavermis

	†Omnidens

	†Pambdelurion

†Opabiniidae

†Caryosyntrips

†Radiodonta (e.g. Anomalocaris)

	Deuteropoda (modern arthropods)

Watch videos about MegadictyonExplainers and documentaries on YouTube (opens in a new tab)

Sources and credits

This article is adapted from the Wikipedia article “Megadictyon”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.

Images, from Wikimedia Commons:

20191118 Megadictyon cf. haikouensis.png by Junnn11, CC BY-SA 4.0

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