Isoxys paradoxus Arthropod from Chengjiang Maotianshan Shales

Isoxys paradoxus

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

Size: 40 mm long

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

Isoxys paradoxusDescription: This unusual arthropod is known as Isoxys paradoxus. The species is known mostly from the distinctively–pointed bivalved carapace. 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 genus is only rarely preserved with any soft parts evident, and only in the species Isoxys auritus. Based upon the few known examples, it had a long segmented body, Isoxysforwardly-projecting stalked eyes, and short antennae. The swimming appendages and most other soft parts only protruded slightly from their protective shell. The other two species: I. paradoxus and I. curvirostratus have an elongated posterior projection. This one is Isoxys paradoxus. This taxon is known only from the Chengjiang Biota, but other members of the genus are found in deposits in Europe, Australia, and North America.

Also see: Chengjiang Biota List Chengjiang Fossils

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