Fuxianhuia protensa, Unusual Soft-bodied Chengjiang Arthropod Fossil

Fuxianhuia protensa

Phylum Arthropoda

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

Size: (25.4mm=1 inch): 28 mm long on a 70 mm by 55 mm matrix

Fossil Site: Chengjiang, Maotianshan Hill, Yuxi, Chengjiang County, Qiongzhusi Section, Yu'anshan Member, Heilinpu Formation, Yunnan Province, China

Fuxianhuia protensaDescription: This unusual arthropod is known as Fuxianhuia protensa. The species is known from several hundred examples, with this one from the most famous location of all, Maotianshan (Mao Tian Hill), site of the discovery of the Chengjiang Biota by Hou Xian-guang in 1984. 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 systematic position of this taxon is still under debate, with some considering it a basal euarthropod. The discoverer of the Chengjiang Biota and a coworker erected a new family and a new superclass called Proschizoramia which was characterized as a group at any early stage in the evolution of arthropods with biramous limbs. As a positive/negative pair, it is a highly desirable specimen due to its association with the Chengjiang Biota that made up a glimpse of the Cambrian Explosion some 5-10 million years before the Burgess Shale fauna came into being. The taxon is unknown outside the Chengjiang Biota. This one is only missing the elongated posterior section which was not collected.

click fossil pictutes to enlarge

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