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

Description: 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 Phylum 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