Soft Bodied Trilobite Misszhouia with Preserved Antennae
from the Chengjiang Biota

Misszhouia (Naraoia) longicaudata

Phylum Arthropoda, Naraoiidae Trilobite Relatives

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

Size: 15 mm long

Fossil Site: Chengjiang Maotianshan Shale, Quiongzhusi Section, Yu’anshan Member, Heilinpu Formation Maotianshan Hill, Yuxi, Chengjiang County, Yunnan Province, China

Misszhouia (Naraoia) longicaudataDescription: 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 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. Misszhouia longicaudata was initially placed within Naraoia, but was given its own genus based upon differences between it and Naraoia compacta of the Burgess Shale.

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 Misszhouiadiscovery 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 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, with most of the soft cuticle, a few legs, and the antennae preserved. Even if it is not a true trilobite, it is sure to be a coveted addition to any collection, one of historical significance due to its ties with the discovery location of the Chengjiang Biota. What makes this one even more unusual is the fact that portions of the anatomy other than the cuticle are not commonly seen.

click fossil pictures to enlarge

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