The
Kaili Biota of Guiznou Province China, like the fantastic Chengjiang
and Burgess Shale Fauna, preserve some of the earliest radiations
of complex life known on the planet. The formation is some 220
m in thickness and spans the Late Early to Early Middle Cambrian.
As such it is intermediate in age between the Changjiang and
Burgess Shale Faunas. Representatives of some 110 genera are
known, representing 11 phyla. The Kaili Biota includes both
soft-bodied and skeletonized animals, and is dominated by trilobites.
It shares roughly 30 genera in common with Chengjiang and nearly
40 with the Burgess Shale. There are also a number of eocrinoid
Echinoderms,
with three members of the gogiid genus Sinoeocrinus predominating.
The Echinoderms remained a modest component of the Cambrian
biota until favorable environmental shifts allowed for a rapid
radiation. A second location has been found some 100 km to the
southwest of the original site recently, affording additional
opportunities to study this diverse faunal assemblage. The presence
of Burgess Shale–like fauna over a large part of southwestern
China shows that the faunal community was quite cosmopolitan
in nature, indicating that fossil
preservation was more of a factor in finding these concentrations
of animals than was the existence of isolated communities suitable
for harboring these myriad life forms. Indeed, some researchers
believe that high rates of uplift and erosion led to increased
deposition of fine sediments in the continental margins, making
such exquisite preservation possible. As a consequence, some
deem the stepwise evolution of
life as more illusion than fact. Whatever the case, these and
future discoveries will go a long way towards providing a clearer
picture of this wonderful time in the evolution of life on earth
we call the Cambrian
Explosion.
Kaili
References
