Nematomorph Worm Death Assemblage from Chengjiang Biota
"fossils of the Cambrian Explosion"

Cricocosmia jinningensis

Phylum Nematomorpha

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

Size: 25 to 73 mm long

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

Cricocosmia jinningensisDescription: This Nematomorph worm is known as Cricocosmia. The species is known from numerous specimens, many of which have preserved details such as this fine example. The intestine is often preserved as a dark film as seen here, indicative of its deposit-feeding lifestyle. What is not typically seen preserved are the cone-shaped sclerites seen in paired longitudinal rows. The diversity of soft-tissue fossils is astonishing: algae,Cricocosmia 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.

This group of worms is commonly known as the horsehair worms, and is represented by some 300 extant species. 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.

Also see: Chengjiang Biota List Chengjiang Fossils

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