Misszhouia
(Naraoia) longicaudata
Arthropoda,
Naraoiidae
Geological
Time: Early Cambrian (~525 million years ago)
Size (25.4
mm = 1 inch): Fossil is 11 mm long by 7 mm wide on a 25 mm by 30 mm
matrix
Fossil
Site: Maotianshan Shales of Chengjiang, Quiongzhusi Section, Yu’anshan
Member, Heilinpu Formation, Mafang Village, Anning, Kunmuing, Yunnan,
China
Code: CJF595
Price: $165.00
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 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, and 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 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.
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