Description
Genuine Pseudogrammoceras fallaciosum Ammonite Fossil
This carefully chosen fossil is a genuine Pseudogrammoceras fallaciosum ammonite from the historic Upper Lias deposits of Bredy Wood, near Stroud, Gloucestershire, UK. Dating from the Toarcian Stage of the Lower Jurassic, this specimen represents a marine cephalopod that inhabited the seas covering Britain approximately 184–174 million years ago.
The listing photograph shows the actual fossil specimen you will receive, allowing its natural preservation, colouration, matrix and individual geological features to be examined before purchase. Full sizing and scale information can be seen in the accompanying photograph.
Lower Jurassic Upper Lias Geology
The traditional term Upper Lias refers to a succession of Lower Jurassic marine rocks deposited during the later part of the Early Jurassic. These strata include mudstones, shales, marls and locally developed limestone beds formed on a marine shelf that extended across much of what is now southern and central England.
During the Toarcian, Gloucestershire lay beneath a broad sea connected to the wider north-west European marine basin. Fine sediment settled through the water column and accumulated across the seabed, preserving the remains of ammonites, belemnites, bivalves, brachiopods and other marine organisms. Variations in water depth, oxygenation, sediment supply and sea level produced a complex succession of fossil-bearing horizons.
The Upper Lias is especially important to palaeontology because it contains distinctive ammonite assemblages that allow geologists to correlate individual rock layers across Britain and continental Europe. Ammonites evolved relatively rapidly and were widely distributed, making their shells valuable index fossils for determining the relative age of Jurassic strata.
Pseudogrammoceras Ammonite Morphology
Pseudogrammoceras belongs to a group of elegant, generally compressed ammonites characteristic of the Toarcian. Its shell was planispirally coiled, with the whorls growing around a central umbilicus in a single plane. Members of the genus are typically recognised by their comparatively slender shell form, defined outer margin and curved ribbing across the flanks.
The ribs may develop from the umbilical region and sweep forward or curve gently as they approach the outer part of the shell. Rib strength, spacing and curvature can vary according to the animal’s growth stage and the preservation of the individual specimen. The venter, or outer edge of the coil, may appear relatively narrow and can carry a keel-like structure characteristic of many hildoceratid ammonites.
The ammonite’s shell was divided internally into a series of chambers. The living animal occupied the final and largest body chamber, while the older chambers formed the phragmocone. These chambers contained varying proportions of gas and liquid, helping the animal regulate buoyancy as it moved through the Jurassic sea.
Although ammonites are often compared with the modern chambered nautilus because of their coiled shells, they belonged to a distinct extinct branch of the cephalopods and were more closely related within the wider group to squid, cuttlefish and octopuses.
Scientific Classification and Fossil Details
Fossil type: Ammonite
Scientific name: Pseudogrammoceras fallaciosum
Family: Hildoceratidae
Superfamily: Hildoceratoidea
Order: Ammonitida
Geological period: Jurassic
Geological epoch: Lower Jurassic
Geological stage: Toarcian
Traditional rock division: Upper Lias
Locality: Bredy Wood, Stroud, Gloucestershire, United Kingdom
Hildoceratid ammonites are among the most recognisable cephalopods of the Toarcian. Their compressed shells, defined venters and distinctive rib patterns make them scientifically useful for comparing fossil-bearing strata and attractive additions to specialist ammonite collections.
Fossilisation and Natural Preservation
After the ammonite died, its shell settled onto or became incorporated within sediment on the Jurassic seabed. Continued burial protected the remains while compaction and mineral-rich groundwater gradually altered the original shell material. Over millions of years, geological processes transformed the surrounding sediment into rock and preserved the ammonite as a fossil.
Any attached matrix, weathering, mineral-filled areas, small fractures, incomplete sections or variations in surface detail are natural characteristics of a genuine fossil. These features record the effects of burial, fossilisation and exposure and give the specimen its individual appearance. No two naturally preserved ammonites are exactly alike.
Collectable British Toarcian Ammonite
This Pseudogrammoceras fallaciosum fossil is an excellent specimen for collectors of British fossils, Gloucestershire fossils, Lower Jurassic ammonites, Toarcian fossils and Upper Lias palaeontology. Its documented identification and locality also make it suitable for educational displays, geological study collections, natural history cabinets or as a distinctive gift for an ammonite enthusiast.
The fossil has been individually selected for its collectable qualities, and the photographs show the exact piece that will be supplied. It is presented as a 100% genuine specimen and includes a Certificate of Authenticity generic card with a lifetime guarantee.
Full sizing please see photo.
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