Bizarre Hallucigenia Chengjiang Biota Lobopodia
"Holy Grail of Chengiang Fossils"

Hallucigenia fortis

Phylum Lobopodia

Geological Time: Lower Cambrian (~525 million years ago)

Size: Hallucigenia is 18 mm long

Fossil Site: Chengjiang Maotianshan Shales, uiongzhusi Section, Yu’anshan Member, Heilinpu Formation, Mafang, Anning, Yunnan Province, China

Hallucigenia ChengjiangDescription: 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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