Description
Genuine Pictonia densicostata Ammonite Fossil
This listing is for a genuine Pictonia densicostata ammonite fossil from the Kimmeridge Clay Formation at Kimmeridge Bay, Dorset, UK. Dating from the Lower Kimmeridgian Stage of the Upper Jurassic, this specimen represents a classic British Jurassic ammonite from one of the most famous fossil-bearing coastal localities in southern England.
Pictonia densicostata is a highly collectable ammonite species, valued for its attractive ribbed shell form, scientific importance, and close connection with the ammonite biostratigraphy of the Kimmeridge Clay Formation. This fossil is a carefully chosen piece, and the photograph shows the actual specimen you will receive. Full sizing can be seen in the photo.
Geology, Age and Location
This ammonite comes from the Kimmeridge Clay Formation, a major Upper Jurassic rock unit exposed along the Dorset coast and across parts of southern and eastern England. The formation is composed mainly of dark mudstones, organic-rich shales, calcareous bands, and marine sediments deposited in a relatively quiet offshore sea.
The fossil is Lower Kimmeridgian in age, approximately 157 to 155 million years old. This places it within the early part of the Kimmeridgian Stage, an important interval of the Late Jurassic. The Kimmeridge Clay is especially famous for its ammonites, marine reptiles, fish, bivalves, belemnites, and other fossils that record life in the ancient seas that once covered southern Britain.
Kimmeridge Bay, Dorset Jurassic Coast
Kimmeridge Bay is one of the most iconic fossil locations on the Dorset coast. The cliffs and foreshore expose layers of the Kimmeridge Clay Formation, giving collectors and geologists access to a rich sequence of Upper Jurassic marine sediments. This area forms part of the wider Dorset and East Devon Jurassic Coast, internationally recognised for its outstanding geological importance.
The sediments at Kimmeridge Bay were laid down in a marine basin where fine mud accumulated on the seabed. Periods of reduced oxygen helped preserve organic-rich layers, while harder limestone and cementstone bands formed within the sequence. These conditions created an excellent fossil record, making the locality particularly important for the study of Late Jurassic marine ecosystems.
Fossil Type and Species Details
Pictonia densicostata was an ammonite, an extinct marine cephalopod related to modern squid, cuttlefish, octopus, and nautilus. Like other ammonites, it possessed a coiled external shell divided into internal chambers. The living animal occupied the final body chamber, while the earlier chambers helped regulate buoyancy as it moved through the water.
The genus Pictonia is strongly associated with Lower Kimmeridgian ammonite faunas and is important in British Jurassic stratigraphy. Pictonia ammonites typically display a planispiral coiled shell with rounded whorls and well-developed ribbing. The species name densicostata refers to the dense or closely spaced ribbing that characterises the shell ornament in this ammonite group.
Scientific classification places Pictonia within Phylum Mollusca, Class Cephalopoda, Subclass Ammonoidea, Order Ammonitida, Superfamily Perisphinctoidea, and Family Aulacostephanidae. Pictonia species are useful index fossils in the Lower Kimmeridgian, helping palaeontologists and geologists correlate marine rock layers across different areas.
Lower Kimmeridgian Marine Environment
During the Late Jurassic, the area now known as Dorset lay beneath a broad marine basin connected to wider European seas. These waters supported a diverse ecosystem of ammonites, belemnites, bivalves, gastropods, fish, sharks, marine reptiles, and other sea life. Ammonites such as Pictonia densicostata were part of this marine food web, using their chambered shells for buoyancy control while moving through the water column.
The Kimmeridge Clay Formation represents a relatively low-energy offshore setting, where fine sediment settled slowly over time. This environment helped preserve the shells of ammonites and the remains of other marine organisms, creating one of Britain’s most important Jurassic fossil records.
Collectible British Jurassic Ammonite
This Pictonia densicostata ammonite fossil is an excellent specimen for collectors interested in British fossils, Dorset geology, Jurassic Coast material, Upper Jurassic ammonites, Kimmeridge Clay fossils, and scientifically labelled fossil specimens. Its named species, Lower Kimmeridgian age, Kimmeridge Bay locality, and classic ribbed ammonite form give it strong display and educational appeal.
This fossil is a genuine specimen and includes a Certificate of Authenticity lifetime guarantee generic card. The photograph shows the actual fossil you will receive, making this a carefully selected and accurately represented collector’s piece from the Upper Jurassic marine deposits of Kimmeridge Bay, Dorset, UK.
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