Name:
Hyolitha; Linevitus billingsi (Chengjiang)
Age: Early
Cambrian (~525 million years ago)
Size (25.4mm=1
inch): 22 mm long, 5 mm wide and 25 mm long, 5 mm wide on a 51 mm by 23
mm matrix
Location:
Quiongzhusi Section, Yu’anshan Member, Heilinpu Formation, Yuxi,
Chengjiang County, Yunnan Province, China
Description:
The discovery of the Chengjiang Biota by Hou Xian-guang in 1984
brought to light an exceptional largerstatte of the time known as
the Cambrian Explosion. 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
is a member of the Hyolitha, a phylum with problematic affinities,
thought to be related to the mollusks. They are thought to have
lived on the substrate, resting on the flatter side of the shell
for stability. The two stabilizing structures are termed the Helens
(named by C.D Walcott of Burgess Shale fame for his daughter). While
Hyolthids are a common fossil of the Chengjiang Biota, many have
not been described. This one is a member of the genus Linevitus.
Notice that the pair of shells are aligned, possibly indicating
orientation by the turbidity current that carried them to their
death.
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