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Far from being fossilized itself, the science of paleontology
has in the past decade undergone a significant evolution in new
ideas and fundamental concepts, catalyzed by new fossil discoveries
and advances in the related fields of biology and genetic science.
For those familiar with the story of the Burgess Shale fossils,
and the paradigm shift in evolutionary thought that their discovery
created, the Chengjiang Fauna perhaps represents the most important
"next chapter" in the study of the early evolution
of complex life.
The discovery of this extensive Cambrian fossil locality in
the hills of Yunnan Province in China, with it's incredible preservation
of soft-bodied animals, many of which have never been described
before, is continuing to inject a flood of new information into
a volatile and hotly debated field of science.
Although fossils of bizarre Cambrian species from Yunnan Province
have been known since 1912, intensive study of the Chengjiang
Fauna only began in the mid-80's, in the wake of groundbreaking
discoveries made in the Burgess Shale of British Columbia. The
discovery of the Burgess Shale Fauna would have been of great
importance if only for the great diversity of un-described species
found there; however, this fauna lived during the early Cambrian
Period, a time when a great increase in the diversity of the
life occurred, an event dubbed "The Cambrian Explosion".
This event has long been recognized as one of the most significant
in the evolution of
life, but the Burgess Shale Fauna revealed that diversity was
even greater than previously recognized, and that life in the
early Cambrian was morphologically bizarre, ecologically complex,
and fiercely competitive.
These discoveries stimulated a worldwide search for similar rare
localities where the soft tissue and body parts of Cambrian animals
have been preserved.
To Chinese paleontologists working in Yunnan, the hills of
Maotianshan yielded a treasure trove of fossils that in several
respects are superior to those of the Burgess Shale. Due to the
lower degree of sedimentary compaction and metamorphism in the
Maotianshan shales, the preservation of soft body parts is much
better in the Chengjiang Fauna. The
exceptional quality if the fossils has resulted in the description
of many new life forms and has turned the interpretation of some
of the Burgess Shale animals upside-down.
The Chengjiang Fauna also predates the Burgess Shale Fauna
by almost 15 million years. It has many examples of very primitive
forms of complex life that may have lived at the very epicenter
of the Cambrian Explosion.
Professor Degan Shu of Northwestern University Xian in China
has recently interpreted a Chengjiang animal as the earliest
Hemichordate, a now rare phylum of animals which share features
of both invertebrate and chordate (or pre-vertebrate) life. Such
discoveries bring our knowledge a few steps closer to the common
ancestors of all complex life.
But perhaps the most suprizing feature of the Chengjiang Fauna
is it's very location in China, which during the Cambrian was
separated from the Canada and Greenland by an ocean almost as
wide as a third of the Earth's circumference. That similar forms
of life in the Cambrian are found so far apart suggests that
some of these animals had a worldwide
distribution. How these animals were so successful in populating
the earth's oceans is still now well understood, but new discoveries
in the Chengjiang Fauna and other localities are still being
made that promise to reveal the mysteries of life in the Cambrian. |
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