This fine fossil is Yunnanozoon lividum, has been designated as
the earliest known hemichordate. Possessing many of the characteristic
chordate features and providing an anatomical link between invertebrates
and chordates, the Hemichordata is a minor but important phylum
in evolutionary biology.
at one point Yunnanozoon was thought to be a member of the Phylum
Chordata, but has been reassigned as mentioned above. This one comes
from the Chengjiang deposits near Anning, Yunnan Province, China.
The diversity of soft-tissue fossils is astonishing: algae, medusiforms,
sponges, priapulids, annelid-like worms, echinoderms, arthropods
(including trilobites), hemichordates, chordates, and the first
agnathan fish make up just a small fraction of the total.
problematic forms are known as well, some of which may have represented
failed attempts at diversity that did not persist to the present
day. As the earliest of the hemichordates, its study casts light
upon the early evolution of both the chordates and the vertebrates
that sprung from them as the story of life unfolded. The linear
structure is the gut, which in some specimens is filled with silt,
an indication that it derived sustenance by ingesting the mud of