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Pomona
College Professor Uncovers Bizarre Lifestyle of
Trilobites
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 Elrathia kingii, the world’s most familiar trilobite fossil,
found in rock shops and museum and university collections
worldwide, lived a bizarre lifestyle as possibly the first
among Earth’s few lifeforms to flourish without benefit from
the sun, or photosynthesis, according to new research by
Pomona College Visiting Professor of Geology Robert Gaines.
“We propose that Elrathia kingii, the ‘world’s most famous
trilobite,’ represents the oldest known example of an
animal-microbial symbiosis, a finding that has important
ramifications for the nature and development of the earliest
animal ecosystems on the planet,” said Gaines.
Gaines and co-author Mary L. Droser of the University of
California, Riverside, reported their findings in an article
titled “Paleoecology of the familiar trilobite Elrathia
kingii: An early exaerobic zone inhabitant,” published in
November by Geology, the journal of the Geological Society
of America.
Trilobites are hard-shelled, segmented creatures that
originated more than 500-million years ago in the Earth's
ancient seas, long before life existed on land. They
appeared in the Cambrian period, during the dawn of animal
life, became extinct before dinosaurs came into existence
and are one of the key signature fossils of the Paleozoic
Era, the first era to exhibit a proliferation of the complex
lifeforms that established the foundation of life as it is
today. Trilobites were arthropods, and their relatives
include crabs and insects.
E. kingii, one of more than 15,000 species of trilobites
presently known, lived in dark, oxygen-depleted ocean waters
in what is now western Utah. It was the only animal among
its contemporaries that could survive in these harsh
conditions, and due to this unique adaptation, it was able
to tap into an abundant food source: sulfur oxidizing
bacteria. These bacteria, which do not need sunlight to
survive, served as the base of a very short food chain.
A similar, but much, much younger, example of an ecosystem
that thrives without photosynthesis are the hydrothermal
vent and seep communities of the deep sea, seemingly hostile
environments that nonetheless support hundreds of species.
Scientists first discovered the deep-sea vents and seeps in
1977, and they became the first ecosystems on Earth known to
prosper without the sun’s rays. Before that, most biologists
believed that only sunlight, through photosynthesis, could
support life on Earth.
Now, the discovery of E. kingii’s alternative lifestyle
pushes the minimum age for the establishment of such
unusually-rooted ecosystems back considerably – placing the
origin of non-photosynthesis-based communities close in time
to the dawn of animal life. |
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