MUSEUM Chengjiang Biota Lobopodian Onychodictyon

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 several legs and six of the scerotzed plates apparent. The plates are reminiscent of those found on Microdictyon, and are thought by some to represent primitive eyes. What is even more interesting is that four of the claws referred to earlier are preserved disarticulated from the limbs. This is only the SECOND time I have ever seen the claws preserved, and the FIRST in which the sclerites are preserved in such detail.