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Meet
the team
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A
free public resource dedicated to showcasing the prehistoric world.
© 2008.
Discovering Fossils is fully independent and works in partnership with
JuniorGeo.
What
is an ammonite?
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Fossil
Collecting Code
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What
ammonites may have looked like. |
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A
fossilised ammonite shell. |
Ammonites
are perhaps the most widely known fossil, possessing the typically ribbed
spiral-form shell as pictured above. These creatures lived in the seas between
240 - 65 million years ago, when they became extinct along with the dinosaurs.
They belong to a group of predators known as cephalopods, which includes their
living relatives the octopus, squid, cuttlefish and nautilus (see pictures
below).
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Octopus |
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Squid
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Cuttlefish
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Nautilus |
The
name 'Ammonite' originates from the Greek Ram-horned god called Ammon.
How
did Ammonites evolve?
These
sea creatures first appeared 415 million years ago in the form of a small,
straight shelled creature, known as Bacrites. They quickly evolved into a
variety of shapes and sizes including some shaped like hairpins. During
their evolution the ammonites faced no less than three catastrophic events that
would eventually lead to their extinction. The first event occurred during
the Permian (250 million years ago), where only 10% survived. These surviving
species went on to flourish throughout the Triassic, however at the end of this
period (206 million years ago) they faced near extinction, when all but one
species survived. This event marked the end of the Triassic and the beginning
of the Jurassic, during which time the number of ammonite species grew once
more. The final catastrophe
occurred at the end of the Cretaceous period when all species were annihilated
and the ammonites became extinct. This event apparently coincided with the death of the
dinosaurs.
How
did Ammonite live?
Ammonites
began life as tiny planktonic creatures less than 1mm in diameter. In their
infancy they would have been vulnerable to attack from other predators, including
fish. However, they quickly assumed a strong protective outer shell that shielded their soft interior from damage. Evidence suggests that they
gained in size rapidly, with females growing up to 400% larger than the males.
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A
baby ammonite. |
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A
large adult ammonite.
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Ammonites moved by jet propulsion, expelling water through a funnel-like opening to propel themselves in the opposite direction.
They typically lived for two years, although some species survived beyond this and
grew very large as pictured above. Evidence of their short
lives is estimated by looking at their living relatives - the nautilus. These creatures exist within modern day seas and possess many
characteristics similar to ammonites (see picture below).
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Living
nautilus found in tropical seas around the world. |
Nautilus
shells comprise of individual chambers, each growing in size as the creature
grows. These chambers are secreted by the creature at a rate of one every
four weeks, equal to 13 each year. Using this as a guide an ammonite shell
containing 26 chambers could be assumed to have housed the creature for two
years. Like the nautilus, ammonites retained their original shell
throughout their life. However it's worth noting that in comparison to
modern day nautili which live in cold, deep water, ammonites preferred warm
shallow waters and may have had a higher metabolism. Consequently, it's
possible that ammonites could reach larger sizes far quicker than modern day
nautili.
Ammonites
were the predators of their time, feeding on most living marine creatures
including molluscs, fish and even other cephalopods. By analogy to modern
cephalopods, their method of attack
probably comprised of silently stalking their prey, then rapidly extending their tentacles
to grasp the target. Once caught the prey would be devoured by the
ammonite's powerful jaws, located at the base of the tentacles, between the eyes.
Much
of the ammonite's life was spent in shallow waters. The evidence to support
this includes their diet, which could be found in the greatest volumes in the
warm shallows. It is also unlikely that their shells could withstand the
high pressures present in deep water (over 100 meters). Other theories based
around their social behaviour suggest their shells were decorated by an array of
patterns, indicating that colour/good light played a large part in their lives.
What
does the shell reveal about the ammonite?
Most
ammonite shells are
coiled, and all contain a series of linked chambers. The
body of the ammonite was contained within the large final, open-ended section called the 'living'
or 'head chamber', from
which the tentacles were extended to catch prey. The opening of the shell - called
the aperture - was possibly covered by a protective shield that could shut to protect the
ammonite from other predators.
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A living nautilus
predates on a crab. |
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Sliced nautilus shell showing chambers.
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As the animal grew, new chambers were added behind the head chamber. The
chambered interior of the shell is referred to as the phragmocone, and in life
this contained gasses which enabled the ammonite to regulate its buoyancy within
the water column. A small tube called the 'Siphuncle' links the chambers.
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A polished
ammonite phragmocone. |
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Another polished ammonite.
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Some
ammonite fossils bear intricate patterned details on their outer surface called 'Sutures'.
These are located beneath the external shell wall, and are often visible if the
fossil has been subject to weathering or artificial polishing. These
patterns mark where the walls of the chambers, 'Septum', meet the outer wall of
the ammonite shell. The bulk of the septum is relatively flat, but becomes
folded
where it meets the outer shell. This method of construction is thought to
have provided strength to the shell when diving to deeper depths. Suture
patterns are very useful for distinguishing different species of ammonite.
Join
us on a fossil hunt...
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Portland
dinosaur hunt
- Sunday 13th July '08 |
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Ever
wished you could walk with dinosaurs? Now you can!
Discover
the hidden secrets of Portland (Dorset), on a quarry tour with local
expert and geologist Chris Pamplin, accompanied by the
Discovering
Fossils & JuniorGeo team. Participants will see dinosaur
trackways and foot prints, fossil trees, giant ammonites,
prehistoric beaches and the Portland Sculpture park.
There
will be some opportunities to collect fossils, but the main
attraction of dinosaur footprints cannot be collected except with a
camera!
This
event requires driving between quarries. Full
details will be provided to participants prior to the event.
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Adults
£10 / Children £5
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Charmouth
to Seatown fossil hunt
- Sunday 20th July '08 |
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A
classic Jurassic fossil hunt!
Join
local expert and geologist Chris Pamplin to explore one of the most
famous stretches of the Jurassic Coast, from Charmouth to Seatown,
taking in Golden Cap.
This
classic fossil locality is where Mary Anning found many of her
remarkable fossils around 190 years ago! The day will include an
informative talk with Chris followed by the fossil hunt
(approximately 4 hours) to Seatown in the east, where you can catch
a bus or taxi back to Charmouth. Participants will all have an
opportunity to find and keep a selection of Jurassic fossils,
including ammonites, belemnites and even marine reptile bones with a
bit of luck!
Full
details will be provided to participants prior to the event.
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Adults
£10 / Children £5
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Cotswold
quarry fossil hunt
- Saturday 26th July '08 |
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Join
local fossil expert Dr Neville Hollingworth on a guided visit of
Colne Gravel Quarry in Gloucestershire to examine and collect from
the highly fossiliferous Jurassic deposits. Recent finds include the
bones and teeth of Ichthyosaurs, Plesiosaurs and crocodiles!.
Uncrushed fossil tree trunks and branches are also common. In
addition the Ice Age river gravels yield common Mammoth and other
remains including horse, mammoth, deer and straight-tusked elephant
bones.
This
trip will provide everyone with an opportunity to find something
rare or unusual. Following an introductory talk, participants will
be able to spend a whole day on site and advice will be given on
collecting and conservation techniques.
Full
details will be provided to participants prior to the day.
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Adults
£10 / Children £5
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Quantoxhead
(Somerset) fossil hunt
- Saturday 9th August '08 |
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Join
geologist Bill Verkaik on a guided tour of the famous Jurassic coast
of north Somerset. Quantoxhead has yielded some of the largest and
well preserved ammonites and marine reptiles in the country. The day
includes an introduction to the geology and fossils of the area,
followed by a guided fossil hunt along the coast. Everyone will have
an opportunity to find a variety of fossils.
Suitable
for all ages and levels of experience, including families.
Full
details will be provided to event participants prior to the day.
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Adults
£10 / Children £5
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Charmouth
to Lyme Regis fossil hunt
- Sunday 17th Aug '08 |
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Join
local expert and geologist Chris Pamplin to explore one of the most
famous stretches of the Jurassic Coast, from Charmouth to Lyme
Regis, taking in Black Ven.
This
classic fossil locality is where Mary Anning found her remarkable
fossils around 190 years ago! The day will include an informative
talk with Chris followed by the fossil hunt (approximately 4 hours)
to Lyme Regis, where you can catch a bus or taxi back to Charmouth. Participants
will all have an opportunity to find and keep a selection of
Jurassic fossils, including ammonites, belemnites and even marine
reptile bones with a bit of luck!
Full
details will be provided to participants prior to the event.
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Adults
£10 / Children £5
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Bracklesham
Bay fossil hunt
- Saturday 27th Sep '08 |
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Bracklesham
Bay is one of the lesser known, but highly productive fossil
collecting locations in the UK.
Discovering
Fossils and JuniorGeo will be joined by local expert and author
David Bone for a guided fossil hunt along the 46 million year old
coast towards Selsey.
The
day includes a 45 minute presentation at the nearby Fishbourne Roman
Palace, which introduces the geology and fossils of the local area
and provides an opportunity to see some of the best fossils
recovered from Bracklesham over the years. Participants will be
shown where to find a range of fossils, including: shark and ray
teeth, fish vertebrae, and if we're lucky, turtle carapace and
crocodile bones and teeth.
Full
details will be provided to participants prior to the event.
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Adults
£10 / Children £5
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Hastings
dinosaur hunt
- Saturday 22nd Nov '08 |
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A
prehistoric experience with local expert Ken Brooks along the famous
dinosaur hunting grounds at Hastings.
During
this event we'll be looking for fossil teeth and bones from animals
that lived in the area from 140 to 120 million years ago. Molluscs,
fish, crocodiles and turtles inhabited lakes and rivers, while the
land was dominated by dinosaurs such as Iguanodon, Polacanthus and
Baryonyx. The sandstones and clays also contain the fossilised plant
remains of ferns, horse-tails, cycads, conifers and tree-ferns - as
well as footprints left by dinosaurs.
Full
details will be provided to participants prior to the event.
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Adults
£10 / Children £5
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Future
fossil hunts - register
your email for event notifications
CLICK
HERE |
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Printing
guidelines: Discovering Fossils is designed to be printed in
landscape (horizontal) format; printing in portrait format will
result in text being missed. To print selected pages, simply
select print from your internet browser and specify landscape from
the printer's 'Properties' menu. Printing is permitted for
non-commercial use and is subject to international copyright law. If
you experience any difficulties printing or have a question
regarding the use of printed materials please contact us for further
information. |
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Safety
notice: Fossil hunting can at times pose a risk to personal safety, in
particular within environments close to the coast, cliffs or in quarries
and when using the tools and equipment illustrated. Discovering Fossils
provides a free resource to inform you about this fascinating subject and
does not accept any liability for decisions made using this information.
We recommend all individuals abide by the 'National Fossil Hunting Code'
and independently research the potential dangers before and during the
visit.
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Written
and designed by Roy
Shepherd
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