Description
This listing offers a RARE Fossil Chalk Echinoid – Plesiocorys (formerly Sternotaxis), a beautifully preserved specimen discovered in the Cretaceous chalk deposits of Sussex, England. This is a superb example of an infaunal sea urchin from the iconic white chalk seas of southern Britain.
As with all our fossils, this is a 100% genuine specimen, carefully hand-selected and accompanied by a Certificate of Authenticity. The actual fossil shown in the photographs is the one you will receive. Please refer to the scale photo (each square/cube = 1cm) for full sizing.
Fossil Overview:
- Genus: Plesiocorys (previously referred to as Sternotaxis)
- Common Name: Fossil Sea Urchin / Chalk Echinoid
- Geological Period: Late Cretaceous
- Stage: Likely Santonian–Campanian (~86–72 million years ago)
- Formation: Upper Chalk Formation
- Location: Sussex, England, UK
- Preservation Type: Test in white chalk matrix
Geological & Depositional Environment:
The chalk formations of Sussex were laid down in the Late Cretaceous in a warm, shallow, epicontinental sea, teeming with calcareous plankton (especially coccolithophores). This fine-grained calcium carbonate mud slowly accumulated to form the thick chalk sequences of southern England.
Plesiocorys echinoids are typical of these chalk beds, often found in quiet, low-energy marine environments ideal for preserving delicate echinoderm tests. These conditions supported a rich diversity of marine life including ammonites, bivalves, brachiopods, and a wide variety of echinoids.
Taxonomy & Classification:
- Phylum: Echinodermata
- Class: Echinoidea
- Order: Holasteroida
- Superfamily: Holasteroidea
- Family: Holasteridae
- Genus: Plesiocorys (formerly Sternotaxis)
- Species: Undetermined
Morphological Features:
Plesiocorys is a distinct genus within the Holasteridae, with features including:
- A subovate to slightly domed test
- A broad anterior sulcus (groove)
- Bilateral symmetry with a sunken peristome (mouth)
- Posteriorly placed periproct (anus)
- Petaloid ambulacra on the aboral surface
These features suggest a burrowing (infaunal) lifestyle, likely living beneath the seafloor and feeding as a deposit feeder.
Notable Information:
- A rarer member of the chalk echinoid fauna
- Represents the transition of nomenclature from Sternotaxis to Plesiocorys, reflecting updated scientific classification
- Excellent preservation in natural chalk matrix
- A highly collectible fossil for palaeontology enthusiasts, educators, and display
Why Buy From Us?
- All fossils are 100% genuine specimens
- Includes a Certificate of Authenticity
- You receive the exact fossil shown in the listing photos
- Safe packaging and fast dispatch
Capture a rare and scientifically fascinating moment in Earth’s marine history with this Plesiocorys echinoid from the Cretaceous chalk of Sussex – a beautiful addition to any fossil collection or educational display.
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