Microdictyon Mueseum Quality Chengjiang Biota Lobopodian

Microdictyon sinicum

Phylum Lobopodia

Geological Time: Early Cambrian, Quiongzhusi Section, Yu’anshan Member, Heilinpu Formation (~525 million years ago)

Size: 22 mm long

Fossil Site: Chengjiang Maotianshan Shales - Mafang, Haikou, Yunnan Province, China

Microdictyon sinicumDescription: The discovery of the Chengjiang Biota by Hou Xian-guang in 1984 resulted in a clear window on what is known as the Cambrian Explosion. The diversity of soft-tissue fossils is astonishing: algae, medusiforms, sponges, priapulids, annelid-like worms, echinoderms, arthropods (including trilobites), hemichordates, chordates, and the first agnathan fish make up just a small fraction of the total. Numerous problematic forms are known as well, some of which may have represented failed attempts at diversity that did not persist to the present day.

The Lobopodians are small marine and terrestrial animals termed colloquially “velvet worms” or “worms with legs”. While all Recent forms are terrestrial, most fossil Lobopodians are marine animals, and are known primarily from the Cambrian. Six named genera, each with a single species, are known from the Chengjiang Biota, making it Lobopodiathe richest source of fossils of the type on Earth.

This is one of the most striking, and quite rare; as of 2004, only some 80 examples were known. The maximum length is 77 mm. It possesses 9 pairs of trunk sclerites which have been likened to the compound eyes of arthropods, so this one is near complete, with several legs evident. While there are some 10 species found in the Cambrian of North and Central America, Europe, Asia, and Australia, only M. sinicum is found in the Chengjiang, and it is the only one based upon more than just sclerites. Microdictyon probably used its clawed feet to attach itself to other creatures, particularly the medusoid Eldonia. Few have ever seen a specimen; even fewer have had the opportunity to obtain one for their collection. As a consequence, I do not expect this one to be available for long.

Also see: Chengjiang Biota Fauna List

click fossil images to enlarge

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