Xidazoon stephanus, An Enigmatic Fossil from Chengjiang Biota
"Part and Counterpart"

Xidazoon stephanus

Phylum Vetulicolia

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

Size (25.4mm=1 inch): 55 mm long by 19 mm across and 50 mm long by 18 mm across on a 70 mm by 35 mm and 85 mm by 38 mm matrix pair

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

Xidazoon stephanusDescription: This unusual fossil is a rare member of the Vetulicolians, an enigmatic group which some scientists place in their own phylum (Phylum Vetulicolia). They are thought to have been swimmers that either were filter feeders or detritivores. One researcher places them with the Urochordates, giving them strong affinity with the XidazoonPhylum Chordata. At present, there is no agreement as to their systematic placement. This specimen comes from the strata immediately above the Chengjiang Boita, and is thus slightly younger, more closely contemporary with the Burgess Shale Fauna of British Columbia. There are three genera typically assigned to the Vetulicola: Vetulicola, Banffia, and Xidazoon. This one is quite unusual with a circular mouth which was thought to have served it in filter-feeding. Seen here as a part/counterpart pair, it is a most unusual member of a most unusual group.

Also see: Chengjiang Biota List Chengjiang Fossils

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