Rare British Chalk Fossil Echinoid – Stereotaxis placenta – Middle Chalk Cretaceous, Birling Gap Sussex UK

Description

For sale is a rare and scientifically significant British Chalk Fossil Echinoid, identified as Stereotaxis placenta, from the Middle Chalk Formation of the Cretaceous Period. This specimen was discovered at Birling Gap, Sussex—one of the most iconic fossil localities along England’s south coast.

Taxonomic Classification:

• Order: Holasteroida
• Superfamily: Holasteroidea
• Family: Holasteridae
• Genus & Species: Stereotaxis placenta

Geological Context:

• Period: Cretaceous
• Stage: Middle to Upper Cenomanian (approx. 96–93 million years ago)
• Formation: Middle Chalk, part of the White Chalk Subgroup
• Depositional Environment: Shallow marine shelf in warm subtropical seas. Fine-grained carbonate mud (coccolith ooze) settled on the seafloor, creating ideal conditions for fossil preservation, particularly of infaunal echinoids.

Morphological Features:

• Disc-shaped or flattened, sub-circular test – a defining feature of Stereotaxis placenta
• Broad anterior sulcus and clearly sunken ambulacral areas
• Apical system slightly offset, with periproct and peristome areas well defined
• Adapted for infaunal burrowing in soft chalky mud, feeding on organic detritus

Scientific Importance:

• Stereotaxis placenta is a rare echinoid with limited stratigraphic distribution, making it useful in detailed biozonation studies of the Middle Chalk.
• Its unusual morphology sets it apart from more commonly found genera such as Micraster or Echinocorys.
• First formally described in the 19th century, this species contributes to our understanding of echinoid evolution and Cretaceous marine ecosystems.

Locality Information:

• Birling Gap, Sussex, UK – part of the renowned Seven Sisters chalk cliffs, this site offers some of the finest Cretaceous chalk exposures in Europe and is a hotspot for collectors and geologists alike.

Authenticity & Display:

All of our fossils are 100% Genuine Specimens and come with a Certificate of Authenticity. The photos in this listing show the actual specimen for sale. The scale rule cube = 1cm. Please refer to the photo for full sizing details.

This specimen has been hand-selected for its rarity, scientific value, and clear morphological features. It’s a superb addition to any palaeontological collection, especially for collectors of echinoids, British fossils, or chalk formation specimens.

Add a rare and beautiful piece of Britain’s ancient marine history to your collection today—an authentic fossil from over 90 million years ago!