is conjectured by some scientists (i.e., Chen et al., Nature
402) to be the oldest member of the craniata in the fossil record.
Their studies purport a phenotype having many vertebrata-like
traits, including brain putative circulatory system, gills, heart,
notochord, musculature, heart with dorsal and ventral aorta,
a posterior projection that might be a proto tail fin, possibly
a pair of lateral eyes and probable pharyngeal teeth, and some
evidence of dorsal and ventral fins.
fossils are found in association with Haikouichthys and Myllokunmingia
consensus are considered to be the oldest
known true craniates and probably the oldest fishes.
(meaning animals with a hard bone or cartilage skull, or more
with heads) is a huge animal clade containing
lampreys and armored jawless fishes, armored fish, sharks,
skates, and rays, spiny sharks, bony fish, reptiles, birds and
earliest craniates are thus of obvious importance to our understanding
of evolution, with Haikouella a prime candidate to be an ancestor
to all vertebrates that have followed, including you.
fossil has three Haikouella measuring some 16 to 22 mm.
Chen, J.-Y.; Huang, D.-Y.; Li, C.-W. (1999). "An early Cambrian
craniate-like chordate". Nature 402 (6761): 518–522.