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
highly sought after specimens from the Chnegjiang Biota: Hallucigenia
fortis. Less than 20 specimens were known as of the publication
of Hou’s book, and few are as complete
as this one, which is missing only the distalmost portion of
the trunk.
The
genus was first discovered in the slightly younger Burgess Shale
of Canada (Hallucigenia sparsa), and was interpreted as walking
on its spikes, rather than the legs as is quite obviously the case
(perhaps the source of the genus name?). It is thought to be most
closely related to Microdictyon,
and may possibly be known from the Kaili Biota as well.
Also
see: Chengjiang
Biota, Chengjiang
Fossils, Cambrian
Explosion
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