Haikouella and Xidazoon, Enigmatic Fossils from Chengjiang
"fossils of the Maotianshan Shales of China"

Name: Haikouella lanceolata and Vetulicolia; Xidazoon stephanus (Chengjiang Maotianshan Shales)

see Kingdon Animalia

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

Size (25.4mm=1 inch): Haikouella: 15-19 mm long Xidazoon: 85 mm long (folded) on opposite sides of a 60 mm by 75 mm matrix

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

Haikouella lanceolataSeen here with different fossils on both the obverse and reverse, it is a very unique specimen from the Chengjiang Biota.

One one side is a mass mortality of Haikouella lanceolata, thought by its describers to be the earliest craniate-like chordate. This fish-like animal has many similarities to the contemporaneous Yunnanozoon lividum, but differs in several aspects: it has a discernible heart, dorsal and ventral aorta, gill filaments, and a neural chord. For all these reasons, Chen, Huang, and Li identified it in the seminal Nature paper (Nature 402, 518-522, 02 December 1999) as a chordate. The debate rages on, but whatever the outcome, this creature was much like the ancestor of all the vertebrates. It derives its generic name from its resemblance to the modern day lancet Amphioxus. Such assemblages have been mentioned in the literature, and must represent some catastrophe that overcame them in mass.

Xidazoon stephanusThe reverse holds an unusual fossil that 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 one is quite unusual with a circular mouth which was thought to have served it in filter-feeding.

click fossil pictures to enlarge

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