here with different fossils on both the obverse and reverse, it
is a very unique specimen from the Chengjiang Biota.
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.
reverse holds an unusual fossil that is a rare member of the Vetulicolians,
an enigmatic group which some scientists place in their own phylum
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.