Cardiodictyon

Cardiodictyon is a genus of lobopodian known from 518 millions years old Chengjiang Lagerstätte. 525 millions years old partial fossil is also reported.^[1] It has ~25 pairs of legs, each associated with a pair of dorsal plates.

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

Fossil specimen, Geological Museum of China

Each leg terminates in a pair of claws.^[2] It may or may not have a head shield,^[3] though it certainly has an expanded head.^[4]

In 2022, a 518 million years old specimen of C. catenulum was researched and shown an unsegmented head and a brain composed of three separate cephalic parts.^[1] However, although "three parts" in this study means prosocerebrum, protocerebrum and deutocerebrum,^[1] it is different from earlier studies that referred protocerebrum, deutocerebrum and tritocerebrum as tripartite brain of arthropod, and treated posocerebrum as part of protocerebrum.^[5][6]

References

1. 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. 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. 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.