Cardiodictyon

Cardiodictyon; Temporal range: Early Cambrian 525–518 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Clade:	Panarthropoda
Phylum:	†Lobopodia
Class:	†Xenusia
Order:	†Archonychophora
Family:	†Cardiodictyidae; Hou & Bergström, 1995
Genus:	†Cardiodictyon; Hou, Ramsköld & Bergström, 1991
Type species
	Cardiodictyon catenulum; Hou, Ramsköld & Bergström, 1991

Cardiodictyon is a genus of lobopodian known from 518 millions years old Chengjiang Lagerstätte. 525 millions years old partial fossil is also reported.

Discovery and naming

Description

It has ~25 pairs of legs, each associated with a pair of dorsal plates. Each leg terminates in a pair of claws. It may or may not have a head shield, though it certainly has an expanded head.

In 2022, a 518,000,000 years old specimen of C. catenulum was researched and shown an unsegmented head and a brain composed of three separate cephalic parts. However, although "three parts" in this study means prosocerebrum, protocerebrum and deutocerebrum, it is different from earlier studies that referred protocerebrum, deutocerebrum and tritocerebrum as tripartite brain of arthropod, and treated prosocerebrum as part of protocerebrum.

Classification

The slightly simplified cladogram below is from a paper by Knecht et al. redescribing the lobopodian Palaeocampa anthrax.

†Diania

†Lenisambulatrix

†Paucipodia

†Thanahita

†Eoconchariidae

	†Microdictyon

	†Fusuchoncharium

	†Quadratapora

	†Xenusion

	†Onychodictyon

†Strictocorniculum

†Rhombocorniculum

†Orstenotubulus

†Carbotubulus

†Hallucigenia fortis

†Hallucigenia sparsa

†"Hallucigenia" hongmeia

†Cardiodictyon

Tardigrada (tardigrades)

†Luolishaniida

	†Ovatiovermis

	†Facivermis

†Luolishania

†Collinsovermidae

†EBS Collinsovermid (SAM P14848)

†Acinocricus

†Collinsovermis

	†Collinsium

	†Entothyreos

†Aysheaiidae

†Aysheaia

Soom Shale lobopodian (C1947)

	†Hadranax

	†Palaeocampa

Antennopoda

†Antennacanthopodia

Onychophora

	†Antennipatus

	†Cretoperipatus

	†Helenodora

	Living onychophorans

(velvet worms)

†Siberiidae

	†Siberion

	†Megadictyon

	†Jianshanopodia

	†Pambdelurion

	†Kerygmachelidae

†Opabiniidae

	†Radiodonta (e.g. Anomalocaris)

	Deuteropoda (modern arthropods)

References

1 2 3 Strausfield, Nicholas J.; Hou, Xianguang; Sayre, Marcel E.; Hirth, Frank (24 November 2022). "The lower Cambrian lobopodian Cardiodictyon resolves the origin of euarthropod brains". Science. 378 (6622): 905–909. Bibcode:2022Sci...378..905S. doi:10.1126/science.abn6264. PMID 36423269. S2CID 253839538. Retrieved 2 December 2022.
↑ Ramsköld, L., & Chen, J.-Y. (1998). Cambrian Lobopodians: Morphology and Phylogeny. In Arthropod fossils and phylogeny (pp. 107–150). New York: Columbia University Press. ISBN 978-0231096546
↑ Bergstrom, J.; Hou, X. (2001). "Cambrian Onychophora or Xenusians". Zoologischer Anzeiger. 240 (3–4): 237–245. Bibcode:2001ZooAn.240..237B. doi:10.1078/0044-5231-00031.
↑ Jianni Liu; Jason A. Dunlop (15 March 2014). "Cambrian lobopodians: A review of recent progress in our understanding of their morphology and evolution". Palaeogeography, Palaeoclimatology, Palaeoecology. 398: 4–15. Bibcode:2014PPP...398....4L. doi:10.1016/j.palaeo.2013.06.008.
↑ Lan, Tian; Zhao, Yuanlong; Zhao, Fangchen; He, You; Martinez, Pedro; Strausfeld, Nicholas J. (2021-10-11). "Leanchoiliidae reveals the ancestral organization of the stem euarthropod brain". Current Biology. 31 (19): 4397–4404.e2. Bibcode:2021CBio...31E4397L. doi:10.1016/j.cub.2021.07.048. ISSN 0960-9822. PMID 34416180. S2CID 237235251.
↑ Lev, Oren; Edgecombe, Gregory D; Chipman, Ariel D (2022). "Serial Homology and Segment Identity in the Arthropod Head". Integrative Organismal Biology. 4 (1) obac015. doi:10.1093/iob/obac015. ISSN 2517-4843. PMC 9128542. PMID 35620450.
↑ Knecht, Richard J.; McCall, Christian R. A.; Tsai, Cheng-Chia; Rabideau Childers, Richard A.; Yu, Nanfang (23 July 2025). "Palaeocampa anthrax, an armored freshwater lobopodian with chemical defenses from the Carboniferous". Communications Biology. 8 (1) 1080. doi:10.1038/s42003-025-08483-0. PMC 12287526. PMID 40702124.

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[Science_nov22-1] 1 2 3 Strausfield, Nicholas J.; Hou, Xianguang; Sayre, Marcel E.; Hirth, Frank (24 November 2022). "The lower Cambrian lobopodian Cardiodictyon resolves the origin of euarthropod brains". Science. 378 (6622): 905–909. Bibcode:2022Sci...378..905S. doi:10.1126/science.abn6264. PMID 36423269. S2CID 253839538. Retrieved 2 December 2022.

[2] Ramsköld, L., & Chen, J.-Y. (1998). Cambrian Lobopodians: Morphology and Phylogeny. In Arthropod fossils and phylogeny (pp. 107–150). New York: Columbia University Press. ISBN 978-0231096546

[3] Bergstrom, J.; Hou, X. (2001). "Cambrian Onychophora or Xenusians". Zoologischer Anzeiger. 240 (3–4): 237–245. Bibcode:2001ZooAn.240..237B. doi:10.1078/0044-5231-00031.

[4] Jianni Liu; Jason A. Dunlop (15 March 2014). "Cambrian lobopodians: A review of recent progress in our understanding of their morphology and evolution". Palaeogeography, Palaeoclimatology, Palaeoecology. 398: 4–15. Bibcode:2014PPP...398....4L. doi:10.1016/j.palaeo.2013.06.008.

[5] Lan, Tian; Zhao, Yuanlong; Zhao, Fangchen; He, You; Martinez, Pedro; Strausfeld, Nicholas J. (2021-10-11). "Leanchoiliidae reveals the ancestral organization of the stem euarthropod brain". Current Biology. 31 (19): 4397–4404.e2. Bibcode:2021CBio...31E4397L. doi:10.1016/j.cub.2021.07.048. ISSN 0960-9822. PMID 34416180. S2CID 237235251.

[6] Lev, Oren; Edgecombe, Gregory D; Chipman, Ariel D (2022). "Serial Homology and Segment Identity in the Arthropod Head". Integrative Organismal Biology. 4 (1) obac015. doi:10.1093/iob/obac015. ISSN 2517-4843. PMC 9128542. PMID 35620450.

[knecht2025-7] Knecht, Richard J.; McCall, Christian R. A.; Tsai, Cheng-Chia; Rabideau Childers, Richard A.; Yu, Nanfang (23 July 2025). "Palaeocampa anthrax, an armored freshwater lobopodian with chemical defenses from the Carboniferous". Communications Biology. 8 (1) 1080. doi:10.1038/s42003-025-08483-0. PMC 12287526. PMID 40702124.