Hallucigenia Chengjiang Biota Lobopodian Association

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 (specimen is pointed to the left). Note the elongated front limbs and the row of spines on the back.

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

It is seen here in association with the bivalved arthropod Isoxys. The species is known mostly from the distinctively–pointed bivalved carapace as seen here. The taxon is only rarely preserved with any soft parts evident. Based upon the few known examples, it had a long segmented body, forwardly-projecting stalked eyes, and short antennae

Also see: Chengjiang Biota Fauna List Chengjiang Fossils