Description
Amaltheus margaritatus Ammonite Fossil
This genuine Amaltheus margaritatus ammonite fossil is a collectible Lower Jurassic marine specimen from Alderton Hill, near Cheltenham, Gloucestershire, UK. Dating to the Upper Pliensbachian stage, this fossil represents an attractive and scientifically interesting ammonite from the ancient Jurassic seas that once covered much of Britain.
The specimen is a carefully chosen piece, with the photograph showing the actual fossil you will receive. It is supplied with a Certificate of Authenticity lifetime guarantee generic card, making it ideal for fossil collectors, natural history displays, educational collections, geology enthusiasts and anyone seeking a genuine British Jurassic ammonite.
Geology, Age and Formation
This fossil dates from the Upper Pliensbachian of the Lower Jurassic, approximately 190 million years old. During this time, Britain lay much closer to the equator than it does today and was covered by warm, shallow epicontinental seas. These seas supported a rich marine ecosystem including ammonites, belemnites, bivalves, brachiopods, crinoids, fish and other marine organisms.
The Alderton Hill area near Cheltenham is associated with classic Lower Jurassic geology of the Cotswold region, including marine sedimentary rocks deposited during the later Pliensbachian. These deposits formed from muds, silts, sands and carbonate-rich sediments that accumulated on the seabed. Over millions of years, these sediments hardened into fossil-bearing rock layers that now preserve evidence of Jurassic marine life.
Ammonites such as Amaltheus margaritatus are especially important in Jurassic geology because they evolved rapidly and were widely distributed across ancient seas. This makes them excellent guide fossils for dating and correlating rock layers. The species is closely associated with the Margaritatus Zone, an important Upper Pliensbachian ammonite biozone.
Fossil Type and Species Details
Amaltheus margaritatus is an ammonite, an extinct marine cephalopod related to modern squid, cuttlefish and nautilus. Ammonites lived inside coiled external shells divided into chambers. The animal occupied the final body chamber, while the empty internal chambers helped control buoyancy as it moved through the Jurassic sea.
The genus Amaltheus is known for its elegant, compressed shell form, moderately open umbilicus and distinctive keel along the outer edge of the shell. Many examples show curved or slightly sigmoidal ribbing across the flanks, often with fine shell ornament that gives the fossil a decorative and highly collectable appearance. The species name margaritatus is historically associated with a pearl-like quality, reflecting the attractive appearance of this well-known Jurassic ammonite.
This ammonite belongs to the family Amaltheidae, within the superfamily Eoderoceratoidea and the order Ammonitida. Amaltheid ammonites are characteristic of the Lower Jurassic and are particularly associated with Pliensbachian marine faunas. The genus Amaltheus was formally named by Pierre Dénys de Montfort in 1808.
Jurassic Marine Environment
When this ammonite was alive, the area that is now Gloucestershire formed part of a broad Jurassic seaway. The seabed would have been inhabited by a variety of bottom-dwelling organisms, while ammonites and belemnites moved through the water column as active marine animals. Ammonites likely fed on small prey and organic material, using their tentacles to capture food while their chambered shells helped them maintain position in the water.
The shell of Amaltheus margaritatus was both functional and visually distinctive. The ribbing and keel helped strengthen the shell and are among the key features used by palaeontologists to identify the species. These natural structures also make Amaltheus ammonites highly appealing display fossils, combining scientific value with natural beauty.
Alderton Hill, Gloucestershire Locality
Alderton Hill, near Cheltenham in Gloucestershire, is a notable locality within the Jurassic geology of the Cotswolds. Fossils from named British localities are especially desirable because they carry strong geological and geographical provenance. This specimen represents a genuine piece of Gloucestershire natural history from a time when the region was part of a warm Jurassic marine environment.
A labelled Amaltheus margaritatus ammonite from Alderton Hill is a strong addition to any collection of British fossils, Lower Jurassic ammonites, Cotswold geology specimens or classic marine fossils. Its combination of recognised species, Upper Pliensbachian age and clear UK locality makes it suitable for display, study, teaching or collecting.
Genuine Fossil with Certificate of Authenticity
This fossil is a genuine specimen and includes a Certificate of Authenticity lifetime guarantee generic card. Full sizing please see photo. The fossil shown in the photograph is the actual specimen you will receive, allowing you to buy with confidence and add a carefully selected, authentic Lower Jurassic ammonite fossil to your collection.
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