Nematomorph Worm Fossil Death Assemblage from Chengjiang

This is an example of a death assemblage of the nematomorphs Maotianshania cylindrical and Cricocosmia jinningensis. The first species is known from numerous specimens, many of which have preserved details, with the taxon named after, Maotianshan (Mao Tian Hill), site of the discovery of the Chengjiang Biota by Hou Xian-guang in 1984. The intestine is often preserved as a dark film, indicative of its deposit-feeding lifestyle. The second is Cricocosmia jinningensis with preserved cone-shaped sclerites seen in paired longitudinal rows. This one was originally thought to be a priapulid worm, a view still held by some researchers. It is only known from the Lower Cambrian of Yunnan Province.

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 fine example preserved here in exquisite detail makes this a highly unique specimen of life from 525 million years ago.