Incertae sedis, Class Coeloscleritophora, Order Chancellorida, Family
Time: Early/Middle Cambrian
mm = 1 inch): Fossil Is 20 mm across by 35 mm long (with spines) on
a 48 mm by 80 mm matrix
Guanshan Fauna, Lower most part of Wulongqing Formation, Caijiachong
Valley, Yieyatoung, Gangtoucun Village, Xiamacun Town, Kunming City,
Yunnan Province, China - Near and similar to the Chengjiang
This fine Chancelloriid fossil comes from what has been termed
the “Guanshan Fauna”, found in the Wulongqing Formation.
The Guanshan Fauna shares many genera with the slightly older
Chengjiang Biota, but differs at the species level. With the
discovery of the Chengjiang Biota in 1984 a window on the Cambrain
Explosion in China was opened. 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.
is an unusual and enigmatic animal known as a chancellorid of
the genus Allonia. The order is named after Chancelloria, another
genus of this strange group of animals. Their precise assignment
as to phylum is still much in dispute. Chancelloria was believed
by C.D. Walcott to be a heteractinellid sponge, a position acceded
to by most researchers until some 30 years ago when it was noted
that the supposed spicules were actually sclerites. As such they
must have been secreted from the inside, rather than being tissue-covered.
These sclerites appear to have function like chain mail armor,
affording protection to the animal. Like sponges, however, they
are thought to have been filter feeders. Typically, only individual
sclerites are preserved; a near complete specimen such as this
is a rare occurrence. Look at my other postings for a large member
of the genus from the Burgess Shale.