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UK Fossils
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Ammonites
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Belemnites
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Bivalves
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The Rest
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Locations
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Strata of Bay
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Sawdon's Road
to Ness
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Ness to Bay
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Bay to Mill
Beck
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Mill Beck to
Stoupe Beck
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Stoupe Beck to
Peak
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Peak to Blea
Wyke
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 Ammonites are probably the best
known fossil of the Yorkshire coast and
it is usually the ammonite that people
are looking for when visiting Robin
Hood’s Bay. So we will start with a
bit of an introduction to this extinct
mollusc. The free swimming ammonites
lived in a period between 408 million
years ago and 65 million years ago. Their
extinction coincides with that of the
dinosaurs. Ammonites took on many
different forms, The classic fossil of
Whitby has got to be Hildoceras Bifrons
with it’s distinctive keel.(the
outer edge) Ammonites are used as zone
fossils due to their relatively rapid
evolution and the wide geographical
distribution.
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 Suture Lines can be seen on some
examples were the shell has become worn.
The suture is the fractal like pattern
formed were the septa, the living
chambers, meet the shell. As the
ammonites evolved the sutural lines
became more complex. The ammonite's
closest living relative is the Nautilus
which, has a very simple suture. The
chambers or septa were connected with a
tube called the siphuncle. This was used
to regulate to animals buoyancy, it is
believed that they operated at depths of
between 50 and 250 meters. The ammonites
propelled them selves backwards by
squirting out jets of water as they
hunted planktonic prey. |
 Aptychi are a rare find. They
are believed to be the lid or operculum
which could be used to seal off the shell
in times of attack by other predators.
This one is from Saltwick Bay to the
north of Robin Hood's Bay. Ammonite finds
will be in hard nodules, which must be
carefully split open, or as impression in
the Jurassic Lias scuars.
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 A Mediaeval
ledgend tells of St.
Hilda the first Abbotess of Whitby been
comfronted by a nest of snakes as she
selected a site for the Abbey, She cast
them off the cliff and as they fell they
turned to stone. Ammonites are sometimes
called snake stone in this area. In
Victorian times reptilian heads were
carved on to specimens to be sold at
inflated prices to unsuspecting tourists.
Around the world there are many other
myths and ledgends associated with these
fossils. Pliny the Elder 23-79AD an
ancient author and scientist called these fossils ammonis
cornua, "horn of Ammon."
Ammon being the Geek ram horned God.
Often the name of ammonite species ends
with ceras, which is Greek for
horn.
Hildoceras
Bifrons. |
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