Misszhouia
longicaudata
Phylum
Arthropoda, Naraoiidae
Trilobite Relatives
Geological
Time: Early Cambrian (~525 million years ago)
Size: 40
mm long
Fossil
Site: Chengjiang Maotianshan Shale, Mafang Section, Yu’anshan
Member, Anning, Kunming, Yunnan Province, 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 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.
This
one is a quite large example which shows the outline of the cuticle,
the central gut line, antennae, and a fringe of delicate biramous
appendages. Few examples as fine as this are ever available, making
this an exceptional specimen for any collection, whether public
or private.
Also
see: Chengjiang Biota for Faunal
List Chengjiang Fossils
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