Naraoia spinosa, Spinose Arthropod from Chengjiang
Often described as a soft bodied trilobite

Name: Naraoiidae; Naraoia spinosa (Chengjiang)

Age: Early Cambrian Qiongzhusi Section, Yu'anshan Member, Heilinpu Formation (~525 million years ago)

Size (25.4mm=1 inch): 26 mm long by15 mm wide on a 59 mm by 85 mm matrix

Location: Maotianshan Hill, Yuxi, Chengjiang County, Yunnan Province, China

Naraoia spinosa soft bodied trilobite chenjiangDescription: The exact taxonomic status of this arthropod is in dispute. It has been termed a "trilobitomorph" by some researchers, showing their beliefs in its close affinity with the trilobites. While the Trilobitomorpha was listed in the Treatise, most now consider that this subphylum is invalid, a catchall much like some of the dustbin terms used by Walcott for a number of the Burgess Shale fauna. Whittington termed Naraioa a "soft-bodied trilobite"' but that belief is not supported at present. Their similarity in appearance to the Agnoistida is purely a result of convergence. Two large groupings of the Paleozoic arthropods are currently in favor: the Crustaceomorpha (which includes Waptia) and the Arachnomorpha, dominated by the trilobites. The Naraoiidae are arachnomorphs and include Misszhouia and Naraoia.

The species is one found in several locations within Yunnan Province, but this one is from the most famous location of all, Maotianshan, site of the discovery of the Chegjiang Biota by Hou Xian-guang in 1984. Indeed, it is this taxon which was first discovered at Maotianshan to start the entire cycle of research.

The diversity of soft-tissue fossils at Jengjiang 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.

This specimen shows many of the classic features of the taxon. Even the diagnostic spines that give the species its name and the central gut are evidence, as is the soft cuticle that betrays the outline of the body.

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