Description
Genuine Sternotaxis plana Fossil Echinoid from Dover, Kent
This carefully selected fossil is a genuine specimen of Sternotaxis plana, an extinct irregular echinoid, or sea urchin, from the historic Chalk Group exposures at Undercliff, Dover, Kent, United Kingdom. Dating from the Turonian Stage of the Upper Cretaceous, this fossil represents an animal that inhabited the warm marine environment covering southern Britain approximately 90–94 million years ago.
The listing photographs show the actual fossil specimen you will receive. Please examine the photographs carefully for the full dimensions, scale, shape, colour, preservation and condition of this individual piece. As a naturally formed fossil, it may display variations in surface texture, mineral colouring, chalk attachment, weathering and preserved anatomical detail. These natural characteristics make every specimen unique.
Fossil Species and Scientific Classification
Sternotaxis plana is a distinctive irregular echinoid belonging to the phylum Echinodermata and class Echinoidea. It is generally classified within the order Spatangoida and family Echinocoridae, a group of specialised sea urchins adapted for living on or within soft marine sediment.
The species was formally described by the pioneering English geologist Gideon Mantell in 1822. It may also appear in scientific and museum records under the name Sternotaxis planus or the combination Plesiocorys (Sternotaxis) plana. These names refer to the same characteristic Upper Cretaceous echinoid widely recorded from the English Chalk.
Distinctive Echinoid Morphology
Unlike regular sea urchins, which commonly possess rounded tests with centrally positioned openings, Sternotaxis plana had a more elongated and bilaterally symmetrical body. Its test, the rigid shell formed from interlocking calcite plates, was typically oval to slightly heart-shaped when viewed from above.
Recognisable features can include a gently domed upper surface, a flatter lower or oral surface and five ambulacral areas containing paired pores through which the living animal extended its tube feet. The mouth was positioned towards the front of the underside, while the periproct, containing the anal opening, occurred towards the posterior end.
This arrangement reflects the directional movement and specialised lifestyle of an irregular echinoid. Depending on preservation, the specimen may retain portions of its overall test outline, plate structure, ambulacral pattern, pore pairs or openings. Please use the photographs to assess the exact anatomical details visible on this particular fossil.
Turonian Chalk Group Geology
This fossil comes from the Chalk Group at Undercliff near Dover, one of Britain’s most celebrated Upper Cretaceous geological areas. The Turonian Stage lasted from approximately 93.9 to 89.8 million years ago and forms an important part of the Late Cretaceous geological record.
The famous white chalk of Dover consists predominantly of extremely fine calcium-carbonate material derived from the microscopic plates of marine plankton known as coccolithophores. After these organisms died, their remains accumulated gradually across the seabed, producing thick deposits of soft carbonate sediment that later compacted into chalk.
The Dover coastal succession exposes extensive sections of the White Chalk Subgroup, including beds of Turonian and younger Cretaceous age. These deposits may contain nodular chalk, marl seams and bands or nodules of flint, together with a diverse assemblage of marine fossils.
Sternotaxis plana Biozone
Sternotaxis plana is closely associated with the traditional Sternotaxis plana Zone of the English Chalk. This biostratigraphical interval is generally placed within the later Turonian and may extend towards the base of the Coniacian in some regional schemes.
The occurrence of this echinoid helps geologists identify and correlate particular levels within Chalk successions across southern England. Fossils used in this way are valuable because their known distribution through geological time allows separate exposures to be compared, even when the individual chalk beds appear visually similar.
The traditional Sternotaxis plana Zone is particularly significant in the study of Upper Cretaceous strata in Kent and Sussex, where it is associated with distinctive chalk beds, marl seams and flint horizons.
Ancient Marine Depositional Environment
During the Turonian, Britain was located farther south than it is today and much of the land was submerged beneath a broad, warm sea. The Dover area formed part of an extensive marine basin connected to the wider north-west European Chalk Sea.
The water was generally clear and far from major sources of sand or terrestrial sediment, allowing microscopic calcareous remains to dominate the seabed deposits. The environment supported a varied ecosystem that included echinoids, bivalves, brachiopods, ammonites, sponges, crinoids, bryozoans, marine worms, fish and sharks.
Sternotaxis plana lived on or partly within the soft chalk mud. Its streamlined, bilaterally symmetrical form was suited to directional movement through sediment, while its tube feet assisted with locomotion, respiration and the collection of organic food particles.
Authentic British Fossil for Display or Collection
This authentic Upper Cretaceous echinoid is ideal for fossil collectors, geology enthusiasts, natural-history displays, educational collections and anyone interested in the remarkable geological heritage of the White Cliffs of Dover.
The fossil is supplied with a generic Certificate of Authenticity card carrying a lifetime guarantee of authenticity. The specimen has been individually chosen for its natural character and collectable appeal, and the photographs show the exact fossil that will be supplied. Full sizing and detailed visual condition information can be seen in the listing photographs.
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