Urokodia aequalis Arthropod from Maotianshan Shales

Urokodia aequalis

Phylum Arthropoda, Subphylum Crustacea (?), Class Thylacocephala (?)

Geological Time: Early Cambrian (~525 million years ago)

Size: 25 mm long if straight

Fossil Site: Chengjiang Maotianshan Shales Quiongzhusi Section, Yu’anshan Member, Heilinpu Formation, Mafang Village, Haikou County, Kunming, Yunnan Province, China

Urokodia aequalaisDescription: This unusual arthropod is known as Urokodia aequalis. The species was described from only a few (~15) examples. With the discovery of the Chengjiang Biota in 1984 a window on the Cambrian Explosion in China was opened. 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.Urokodia chengjiang 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 taxon is only known from Chengjiang, but Hou (1989) notes that it bears some resemblance to the younger Burgess Shale genus Mollisonia that has been found in the younger Kaili Biota of China as well. Its body comprises segments no unlike millipedes. The species derives its name from the equivalent size and approximate appearance of both the posterior and anterior shields. It is thought to have been a bottom-dwelling animal, most likely a scavenger, but little is actually known since the only soft tissue preservation found to date is a stout antenna.

Also see: Chengjiang Biota, Chengjiang Fossils, Cambrian Explosion

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