Soft Bodied Trilobite Naraoia spinosa from the Chengjiang Biota
with Digestive System Preservation

Naraoia spinosa

Arthropoda, Naraoiidae

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

Size (25.4 mm = 1 inch): Fossil is 9 mm long by 9 mm wide on a 33 mm by 25 mm matrix

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

Code: CJF918

Price: Sold


Description: 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 Trilobitoorpha 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 it a “soft-bodied trilobite”’ but that belief is not supported at present. Their similarity in appearance to the Agnostida 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, with this one, Naraoia spinosa, named for the spinose cuticle so well preserved here. The species is one found in several locations within Yunnan Province.

The diversity of Chengjiang Biota 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.

This one shows many of the classic features of the taxon, even the diverticulae (digestive glands) and the central gut are evidence, as is the soft cuticle that betrays the outline of the body. Even if it is not a true trilobite, it is sure to be a coveted addition to any collection. What makes this one even more unusual is the fact that some of the internal organs have been preserved in three dimensions, rather than the typical flat specimens most often seen. The cephalon is still covered by matrix which could be removed to afford an even more impressive specimen. With the recent designation of the Chengiang sites as UNESCO World Heritage locations only examples such as this collected many years ago will be available.

Also see: Chengjiang Biota Fauna List Chengjiang Fossils

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