Sinocylindra is an extinct genus of macroalgae that existed between the Ediacaran and Middle Cambrian periods.

[2][3] It was previously thought by some that S. yunnanensis might be a prokaryotic species in the Siphonophycus genus,[4] however due to elements of its morphology such as the size and length of the species, it was determined to most likely be a eukaryotic algae of a previously unknown genus.

[5] Sinocylindra linearis, like yunnanensis, was cylindrical in shape, with a diameter ranging from 0.3-2.0mm, and a length of 5.0-50 mm.

[2] Sinocylindra yunnanensis was first described in 1991, found in the Upper Doushantuo shales at Chengjiang, in the Chinese province of Yunnan.

[1] Since its discovery, a number of fossils across Southern China have been found, as well as a specimen in the Drumian Marjum formation in Utah, United States.