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Picture Info

Source: Discover Magazine.

Source article


Published By

Dr. Dick van der Wateren


Evolution, Arthropoda, Lobopoda, Cambrian

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Walking cactus may be early relative of arthropods

23.02.2011, Age: 3896 days

A fossil of Diania cactiformis, a strange-looking 6-cm-long creature dating from the Cambrian was found in Yunnan, southwestern China. Its discoverers believe it to be a close relative to the Arthropoda.

Although belonging to a different group of animals, the lobopodian, a group of animals that look like "worms with legs", Diania was “close to the point of becoming a true arthropod” according to the authors of this week's article in Nature.

See also Nature News and online article in Discover Magazine.

Abstract of Nature article

Cambrian fossil Lagerstätten preserving soft-bodied organisms have contributed much towards our understanding of metazoan origins. Lobopodians are a particularly interesting group that diversified and flourished in the Cambrian seas. Resembling ‘worms with legs', they have long attracted much attention in that they may have given rise to both Onychophora (velvet worms) and Tardigrada (water bears), as well as to arthropods in general. Here we describe Diania cactiformis gen. et sp. nov. as an ‘armoured' lobopodian from the Chengjiang fossil Lagerstätte (Cambrian Stage 3), Yunnan, southwestern China. Although sharing features with other typical lobopodians, it is remarkable for possessing robust and probably sclerotized appendages, with what appear to be articulated elements. In terms of limb morphology it is therefore closer to the arthropod condition, to our knowledge, than any lobopodian recorded until now. Phylogenetic analysis recovers it in a derived position, close to Arthropoda; thus, it seems to belong to a grade of organization close to the point of becoming a true arthropod. Further, D. cactiformis could imply that arthropodization (sclerotization of the limbs) preceded arthrodization (sclerotization of the body). Comparing our fossils with other lobopodian appendage morphologies - see Kerygmachela, Jianshanopodia and Megadictyon - reinforces the hypothesis that the group as a whole is paraphyletic, with different taxa expressing different grades of arthropodization.

Jianni Liu, Michael Steiner, Jason A. Dunlop, Helmut Keupp, Degan Shu, Qiang Ou, Jian Han, Zhifei Zhang & Xingliang Zhang. An armoured Cambrian lobopodian from China with arthropod-like appendages. Nature Volume: 470, Pages: 526-530, Date published: (24 February 2011) DOI: doi:10.1038/nature09704 Received 03 October 2010, Accepted 19 November 2010, Published online 23 February 2011.

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