Onychodictyon
ferox
Phylum Lobopodia
Geological
Time: Early Cambrian (~525 million years ago)
Size: Onychodictyon:
53 mm long (if straight)
Fossil
Site: Chengjiang Maotianshan Shales, Quiongzhusi Section, Yu’anshan
Member, Heilinpu Formation, Mafang, Anning, Yunnan Province, China
Description:
The discovery of the Chengjiang Biota by Hou Xian-guang in 1984
resulted in a clear window on what is 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. The Lobopodians are small marine and terrestrial animals termed
colloquially “velvet worms” or “worms with legs”.
While all Recent forms are terrestrial, most fossil Lobopodians
are marine,
and are known primarily from the Cambrian. Six named genera, each
with a single species, are known from the Chengjiang Biota, making
it the richest source of fossils of the type on Earth. This is one
of the most striking, and quite rare; as of 2004,
only some 15 examples were known. The maximum length is 70 mm. It
possesses a sclerotized head shield with 10 paired sclerotic plates,
each associated with a pair of legs. Each leg bears curved claws
which are thought to have served the creature as an adaptation to
crawling on other organisms. It is most closely related to Aysheaia
from the younger Burgess Shale. This one is very detailed, with
the legs and scerotzed plates apparent. What is evn more interesting
is that the anteriormost and posteriormost legs show the claws referred
to earlier. There may even be more of the specimen entombed in the
matrix, waiting for someone with the skill to free them after over
a HALF BILLION years.
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