Naraoia spinosa

Naraoiidae

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

Fossil Site: Chengjiang Maotianshan Shales - Quiongzhusi Section, Yu’anshan Member, Heilinpu Formation, Yuxi Chengjiang County, Yunnan, China

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 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. 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.

Even if it is not a true trilobite, it is sure to be a coveted addition to any collection, one found only as a member of the Chengjiang Biota. This one has some of the cephalic region obscured, so is being offered at a very reasonable price.