Microdictyon
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Microdictyon is an extinct "armored worm" coated with dot-like scleritic scales, known from the Early Cambrian Maotianshan shale of Yunnan China. Microdictyon is sometimes included in a somewhat ill-defined Phylum – Lobopodia – that includes several other odd worm-like and segmented free-swimming animals that do not appear to be arthropods or worms. The phylum includes Microdictyon, Onychodictyon, Cardiodictyon, Luolishania, Paucipodia, as well as the Anomalocarids. The isolated sclerites of Microdictyon are known from other Lower Cambrian deposits. (The famous Hallucigenia from the Cambrian-age Burgess Shales was once considered to belong to the family Lobopodia, but is now recognized as an Onychophoran, a relative of the velvet worms.)
Microdictyon sinicum (Chen, Hou and Lu, 1989) is typical. The wormlike animal has ten pairs of sclerites on the sides, matched to a pair of tentacle-like feet below. The head and posterior are tubular and featureless. A picture can be found at http://paws.wcu.edu/dperlmutr/earlyfauna.html.
The name Microdictyon is also used for a genus of green algae.