Namibia
2008 "Ediacaran
fossils of Namibia"
Issue Date |
08.08.2008 |
ID |
Michel: Scott: Stanley Gibbons:
Yvert: UPU: NA019.08
Category: pR |
Artwork |
Helge Denker, Namibia (design and text) |
Stamps in set |
4 |
Value |
Standard mail ($2.00) - Rangea
Postcard rate ($3.90) - Swartpuntia
Registered non-standard mail ($18.45) - Pteridinium
Registered inland mail piad ($22.95) - Ernietta
|
Size (width x height) |
30.0mm x 40,0mm |
Layout |
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Products |
FDC x1 |
Paper |
|
Perforation |
14x13.25 |
Print Technique |
Offset, four colors |
Printed by |
Joh Enschedé Security Printers, the
Netherlands |
Quantity |
25 000 of each stamp, 1 500 FDCs |
Issuing Authority |
Namibia Post Ltd |
Fossils are pieces in the puzzle of Earths history. They open small
windows onto the past. Fossils have probably been known to people since
the dawn of our time on Earth. Yet the understanding of what fossils
actually are, and the subsequent focused study of them, only began a
little over 200 years ago. Since then, scientists have been seeking to
reconstruct prehistoric life on Earth through the painstaking
examination and reconstruction of fossils and through accompanying
geological research and dating of strata.
A time line of the existence of Earth itself has been mapped out on
what
is called the stratigraphic time table. The divisions of time on this
table are complex. The table is firstly divided into three Eons —
starting with the Archean that begins with the creation of Earth
itself, followed by the Proterozoic and finally the Phanerozoic Eon,
which leads to the present day.
Each Eon is divided into a number of
Eras, which may again be subdivided into different Periods, Epochs and
Ages.
The Ediacaran Age is a division of time within the Neoproterozoic
Era, which itself is a subdivision within the Proterozoic Eon. The
Ediacaran Age came just before the Cambrian Period, which already falls
into the next Eon, the Phanerozoic. The Cambrian is well-known because
it was a time of incredible diversification of life that has become
known as the Cambrian Explosion. The ancestors of most life forms
existing today first evolved during this Period.
The Ediacaran began
around 630 million years ago and ended 88 million years later. For
humans, who seldom live to be older than one hundred years, a million
years is a timespan that is very difficult to grasp. But we know today
that Earth is about four thousand five hundred million years old. Life
on Earth may date back as far as four thousand million years, when the
first micro- organisms might already have developed. The Oldest known
fossils, simple cells with a nucleus, are about three thousand five
hundred million years old.
The Ediacaran fossils are particularly
interesting because they represent the next step after the small,
single-celled organisms that lived alone on Earth for several thousand
million years. Ediacaran life forms are the earliest large and complex,
multi-cellular organisms that have been discovered. To study Ediacaran
fossils is to be amongst the earliest creatures known. The Age is named
after Ediacara, a place in the South Australian outback, where many of
the fossils were discovered in the late 1940s.
But the first fossils
from this Age were already found in 1908 on a farm in southern Namibia.
The Namibian fossils are considered to be amongst the best Late
Proterozoic/Early Cambrian specimens known. Fossils from the same time
period were later found in Russia, Newfoundland, Canada and the United
States.
The Ediacaran creatures are the oldest known organisms
recognizable to the naked eye and the first large, multi-celled
creatures known to have lived on Earth. They appear to be the starting
point in the diversification of life on our planet. They existed in a
wide range of forms and sizes. Many had a quilted structure, with their
forms being divided into a number of chambers like a quilt. They lived
at a time when few predators existed to threaten them. This allowed the
big, mostly immobile species to thrive. As life forms suddenly
diversified during the Early Cambrian, most of the Ediacaran organisms
quickly disappeared. The creatures that now dominated had developed
hard shell and skeletons that fossilize relatively easily, thus leaving
an extensive fossil record. The soft Ediacaran organisms rarely
fossilised and left little evidence to help scientists to understand
and easily classify them.
There is still not complete consensus amongst
scientists about many of the Ediacaran lifeforms. Some experts consider
at least some of them to have been giant single-celled organisms, where
the quilt-like subdivisions allowed the cells to grow to such enormous
sizes. They are so bizarre that they do not fit into the Six previously
defined kingdoms of Animalia, Plantea, Fungi, Protista (single-celled
or simple multi-celled organisms such as algae and some moulds),
Archaebacteria and Eubacteria (unicellular organisms divided into two
kingdoms on the basis of biochemical differences). Most Ediacaran
organisms have been placed in their own kingdom, the Vendozoans. lt is
an extinct kingdom, that has left no modern equivalents.
Many of the
Ediacaran creatures that we know lived in shallow seas with sandy sea
floors covered by a mat of slime produced by bacteria. Under ideal
circumstances, this combination aided the fossilisation of the
soft-bodied creatures, allowing scientists to identify numerous forms.


Swartpuntia
was a large, leaf-shaped organism divided into
fourhorizontally symmetrical parts. It had a distinct stem which is
likely to have anchored it to the sea floor.
Pteridinium was an
elongated, frond-like organism. Specimens longer than 30 cm are known,
but none have been found with both ends intact, making it impossible to
say whether it floated through the water or was anchored to the ground.
Ernietta had a strange, sack-like form and occurred in
clusters on the
sea floor.
Rangea was a compact, symmetrically divided, leaf-shaped
organism, again with a stem-like structure with which it seems to have
been attached to the sea floor.
While it is possible to identify and
classify many of the Ediacaran fossils, scientists can only guess at
the life cycles and living conditions of these enigmatic creatures. We
know the past only from what has been found. And what has been found
still leaves many gaps, which can only be bridged With theories until
evidence may be found to give foundations to them. Much of the past we
will never know, but can only imagine and wonder about.
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References:
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