Pseudoholaster suborbicularis Fossil Echinoid Cretaceous Chalk Dorset UK Authentic Certified | Rare Sea Urchin from Sharpwick Grange

Description

Authentic Pseudoholaster suborbicularis Fossil Echinoid from Dorset

This listing offers a well-preserved Pseudoholaster suborbicularis fossil echinoid, collected from the Cretaceous chalk deposits of Sharpwick Grange, Dorset, UK. Belonging to the order Holasteroida, Pseudoholaster represents a fascinating group of irregular sea urchins that thrived in the chalk seas of the Late Cretaceous. The specimen shown in the photographs is the exact fossil you will receive, with a 1 cm scale cube included for accurate measurement.

All of our fossils are 100% genuine specimens and come with a Certificate of Authenticity, ensuring their provenance and making them suitable for collectors, educators, and natural history enthusiasts alike.

Geological Context – Late Cretaceous, Cenomanian Stage

This fossil originates from the Lower Cenomanian stage of the Late Cretaceous (approx. 100–94 million years ago). During this period, much of southern England was covered by shallow, warm seas, where vast chalk deposits were formed from the remains of microscopic plankton. These conditions created a unique environment that preserved marine fossils with exceptional clarity.

The chalk exposures of Dorset are world-famous for their fossil content, and specimens such as Pseudoholaster suborbicularis are highly valued for both their rarity and their role as important biostratigraphic indicators within the Cenomanian stage.

Fossil Type and Classification

• Species: Pseudoholaster suborbicularis
• Genus: Pseudoholaster
• Order: Holasteroida
• Superfamily: Holasteroidea
• Family: Holasteridae

This species is a member of the Holasteridae family, a group of echinoids adapted to infaunal lifestyles within soft chalk sediments. Their unique morphology and evolutionary adaptations distinguish them from other Cretaceous echinoids such as Micraster and Cardiaster.

Morphological Features

This specimen shows the classic traits of Pseudoholaster suborbicularis, including:

• A rounded, subcircular test (shell) with a relatively flattened profile compared to other spatangoids.
• Slight anterior-posterior elongation, giving the echinoid a distinctive orbicular outline.
• Petaloid ambulacra on the dorsal surface, arranged in a subtle star-shaped pattern.
• A marginally positioned periproct (anal opening), reflecting its specialised adaptation to a burrowing lifestyle.
• A ventrally positioned peristome (mouth) suited to deposit feeding within soft chalk sediment.

These adaptations allowed Pseudoholaster to thrive as an infaunal deposit feeder, buried within the chalky seafloor, where it filtered organic material from sediment.

Scientific and Collector Importance

Pseudoholaster suborbicularis holds significant value in both palaeontology and fossil collecting. Scientifically, it contributes to our understanding of echinoid evolution and palaeoecology during the Cenomanian. Its distinctive form and stratigraphic occurrence make it a useful tool for defining biozones within the chalk successions of Europe.

For collectors, this fossil offers the chance to own an authentic and relatively uncommon echinoid from Dorset’s famous chalk exposures. Its excellent preservation and distinctive morphology make it both a scientific specimen and a striking display piece.

Depositional Environment

The chalk seas of the Cenomanian were shallow, warm marine environments, with stable conditions ideal for marine life. Rich in microscopic algae and plankton, these seas supported abundant organisms, including echinoids, molluscs, and fish. The fine-grained chalk acted as a perfect medium for fossilisation, preserving delicate sea urchins like Pseudoholaster suborbicularis in remarkable detail for millions of years.

Guarantee of Authenticity

Every fossil we sell is a 100% genuine specimen, carefully chosen for its preservation and display quality. Each comes with a Certificate of Authenticity, providing confidence in its provenance. The photographs show the exact fossil you will receive, with scale references for accurate sizing.

This Pseudoholaster suborbicularis fossil echinoid from Sharpwick Grange, Dorset is a rare and scientifically significant piece of England’s Cretaceous past – a genuine sea urchin fossil that combines historical importance with natural beauty.