> in the fossil record. The team found a diversity of fossils, suggesting life
> may have recovered relatively quickly following the first major Snowball
That is pretty cool!
Now, evolution is often 'bushy', esp with new creatures, new habitats, etc. These creatures may or may not have been a 'main' line. Kind of like the Burgess Shale shows a number of creatures, many of which did not survive as a 'main' line.
-Doug
--- In geology2@yahoogroups.com, Lin Kerns <linkerns@...> wrote:
>
> *Scanning electron microscopy images reveal an microscopic, oval-shaped
> shell with tapered ends, from which an organism's feet may have extended.
> The surface of the shell are made up of tiny bits of silica, aluminum and
> potassium, which the organism likely collected from the environment and
> glued to form armor. (Credit: Tanja Bosak)
> *
> Life After 'Snowball Earth': New Fossils Suggest Rapid Recovery of Life
> After Global Freeze
>
> ScienceDaily (June 16, 2011) — The first organisms to emerge after an
> ancient worldwide glaciation likely evolved hardy survival skills, arming
> themselves with tough exteriors to weather a frozen climate.
>
> Researchers at MIT, Harvard University and Smith College have discovered
> hundreds of microscopic fossils in rocks dating back nearly 710 million
> years, around the time when the planet emerged from a global glaciation, or
> "Snowball Earth," event. The fossils are remnants of tiny, amoeba-like
> organisms that likely survived the harsh post-glacial environment by
> building armor and reaching out with microscopic "feet" to grab minerals
> from the environment, cobbling particles together to make protective shells.
>
> The discovery is the earliest evidence of shell building, or agglutination,
> in the fossil record. The team found a diversity of fossils, suggesting life
> may have recovered relatively quickly following the first major Snowball
> Earth event. The researchers report their findings in an upcoming
> issue of *Earth
> and Planetary Science Letters*.
>
> The widely held Snowball Earth theory maintains that massive ice sheets
> covered the planet from pole to pole hundreds of millions of years ago.
> Geologists have found evidence of two major snowball periods -- at 710 and
> 635 million years ago -- in glacial deposits that formed close to the modern
> equator. Fossil records illustrate an explosion of complex, multicellular
> life following the more recent ice age. However, not much is known about
> life between the two major glaciations -- a period of about 75 million years
> that, until now, exhibited few signs of life.
>
> "We know quite well what happened before the first Snowball, but we have no
> idea what happened in between," says Tanja Bosak, assistant professor of
> geobiology at MIT, and the paper's lead author. "Now we're really starting
> to realize there's a lot of unexpected life here."
>
> *Ice Age armor*
>
> Bosak's colleagues, Francis Macdonald of Harvard and Sara Pruss of Smith,
> trekked to northern Namibia and Mongolia to sample cap-carbonate rocks --
> the very first layers of sediment deposited after the first ice age. The
> team hauled the samples back to Cambridge, where Bosak dissolved the rocks
> in acid. She plated the residue on slides and looked for signs of fossilized
> life. "It's a little bit like looking at clouds, trying to pick out shapes
> and seeing if anything's consistent," Bosak says.
>
> Peering at the sludge through a microscope, she discovered a sea of tiny
> dark ovals, each with a single notch at its edge. To get a closer look,
> Bosak used scanning electron microscopy to create high-resolution,
> three-dimensional images, revealing hollow, 10-micron-thick shells. Fossils
> from Namibia were mostly round; those from Mongolia, more tube-like. Most
> fossils contained a slit or neck at one end, from which the organism's
> pseudopodia, or feet, may have protruded.
>
> Bosak analyzed the shells' composition using X-ray spectroscopy, finding a
> rough patchwork of silica, aluminum and potassium particles that the
> organism likely plucked from the environment and glued to its surface.
>
> Bosak says these single-celled microbes may have evolved the ability to
> build shells to protect against an extreme deep-ocean environment, as well
> as a potentially growing population of single-celled species, some of which
> may have preyed on other organisms.
>
> *A Snowball window *
>
> "We can now say there really were these robust organisms immediately after
> the first glaciation," Bosak says. "Having opened this kind of window, we're
> finding all kinds of organisms related to modern organisms."
>
> The closest modern relative may be testate amoebae, single-celled microbes
> found in forests, lakes and peat bogs. These tiny organisms have been known
> to collect particles of silica, clay minerals, fungi and pollen, cementing
> them into a hard cloak or shell. Bosak says testate amoebae were extremely
> abundant before the first Snowball Earth, although there is no robust
> evidence that the plentiful protist evolved its shell-building mechanism
> until after that ice age.
>
> Bosak's guess is that the post-glacial environment was a "brine" teeming
> with organisms and newly evolved traits. She says the group plans to return
> to Mongolia to sample more rocks from the same time period, and hopes other
> researchers will start to investigate rates of evolutionary change in
> similar rocks.
>
> Andrew Knoll, the Fisher Professor of Natural History and professor of earth
> and planetary sciences at Harvard, says the group's findings point to a
> potentially rich source of information about the kinds of life able to
> persist between glacial periods.
>
> "To date, we've known very little about life between the two large ice
> ages," Knoll says. "With this in mind, the new discoveries are truly
> welcome."
> *Story Source:*
>
> The above story is reprinted (with editorial adaptations by
> Science*Daily*staff) from materials provided by
> *Massachusetts Institute of Technology* <http://web.mit.edu/>. The original
> article was written by Jennifer Chu.
>
> ------------------------------
>
> *Journal Reference*:
>
> 1. T. Bosak, D.J.G. Lahr, S.B. Pruss, F.A. Macdonald, L. Dalton, E.
> Matys. *Agglutinated tests in post-Sturtian cap carbonates of Namibia and
> Mongolia*. *Earth and Planetary Science Letters*, 14 June 2011 DOI:
> 10.1016/j.epsl.2011.05.030 <http://dx.doi.org/10.1016/j.epsl.2011.05.030>
>
>
> Massachusetts Institute of Technology (2011, June 16). Life after 'Snowball
> Earth': New fossils suggest rapid recovery of life after global freeze. *
> ScienceDaily*. Retrieved June 17, 2011, from *http://www.sciencedaily.com
> /releases/2011/06/110615132027.htm*
>
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