“Soft- Bodied Trilobite” Misszhouia from Chengjiang
with Exceptional Interior Preservation

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. 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, and it is this taxon which was first discovered at Maotianshan to start the entire cycle of research.

The diversity of soft-tissue fossils from the Maotianshan Shales 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 the diverticulae 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 most unusual is the fact that the diverticulae are made more prominent by the presence of iron minerals which made a fine contrast agent. .