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Michael Collier
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This paleontologist is excavating fossils
in Colorado's Dry Mesa Quarry. It is part of the Morrison
Formation and has a great diversity of animals from the Jurassic
Period. It is considered to be the best quarry in the world
for the Jurassic. Located near Delta, Colorado excavation
at the Dry Mesa Quarry began in 1972.
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A paleontologist collects as many fossils as possible from a rock or
sediment. Once the fossils are prepared by scraping and cleaning, they
are sorted by geometry. Fossils with very similar geometry are assumed
to belong to a single species. Fossils with somewhat different geometry
are assumed to belong to a different species. Usually the fossil species
has already been studied and named. Sometimes, however, the species is
a new one. Then the paleontologist writes a detailed description of the
new species, gives the new species a name, and publishes the description
for others to read and use in their own work. Not much excites a paleontologist
more than discovering a new species!
Sorting fossils is tricky business, for several reasons. Some organisms
died when they were young and still developing, and some died when they
were old. Some were male and some were female. Also, most species show
a lot of natural variability. You know that from looking at other members
of your own species! It's often impossible for paleontologists to decide
whether they are looking at a single species with a lot of variability,
or two similar species.
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| © Marli
Miller, University of Oregon
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Precambrian stromatolites. This sample is
Conophyton - a species of conical shaped stromatolites. Stromatolites,
algae and cyanobacteria were the earliest life forms to populate
the oceans of Earth.
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The oldest fossils are more than three and a half billion years old.
They are simple unicellular (single-celled) algae, very similar to algae
that still exist today. Evolution was very slow until about seven hundred
million years ago, when unicellular organisms with larger and more complex
cells evolved. Not long after that, a little more than half a billion
years ago, multicellular (many-celled) organisms appeared. Instead of
consisting of just a single cell, multicellular organisms have an enormous
number of cells, grouped according to their function. Several kinds of
multicellular organisms evolved in a very short time, geologically. Paleontologists
still do not understand very well how this happened. Many of these early
kinds of multicellular organisms, like clams, snails, and corals, are
still abundant today. More complex kind of animals, like reptiles, birds,
and mammals, evolved even more recently in geologic time.
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