This lovely duo is a personal favourite of mine. A small marvel from a vanished sea — a delightful wee ammonite measuring just 2.6 centimetres across, Anahoplites planns, from the Cretaceous Folkestone Gault Clay of Kent, in southeast England.
Sharing this ancient stage is a 3.2 centimetre section of Hamites sp., one of those wonderfully uncoiled ammonites that seem to have ignored the usual rules of shell design.
Together, they sit upon their original matrix, a handsome slab of Gault Clay — known locally, and rather poetically, as the Blue Slipper.
This fine muddy clay was laid down some 105 to 110 million years ago during the Lower Cretaceous, in the Upper and Middle Albian.
At that time, a calm, fairly deep continental shelf sea spread across what is now southern England and northern France. There were no rivers muddling these waters, no estuarine murk drifting in. The absence of brackish or freshwater fossils tells us this was an open marine setting, clear of freshwater influence and comfortably offshore.
The sea itself was not abyssal, but neither was it shallow. Evidence suggests depths of around 40 to 60 metres. We know this, delightfully enough, from borings made by specialist algal-grazing gastropods, and from studies of foraminifera undertaken by Khan in 1950.
Even the temperatures have been estimated: around 20 to 22 degrees Celsius near the surface, and a cooler 17 to 19 degrees on the seafloor. Quite balmy, really — especially for creatures wearing shells all day.
The Gault is perhaps best known for rather less peaceful behaviour. It is responsible for many of the major landslides around Ventnor and Blackgang on the Isle of Wight, where this slippery clay can transform stable slopes into geological chaos with unnerving enthusiasm.
Yet for fossil lovers, the Gault’s true fame lies in its extraordinary marine fauna, particularly from mainland localities such as Folkestone in Kent — the type locality for the Gault Clay and one of Britain’s most celebrated collecting sites.
The clay yields ammonites in abundance. The Isle of Wight Gault is less generous, though the south-east coast of the island has produced a fine variety of ammonites, especially members of Hoplites, Paranahoplites, and Beudanticeras.
Though less fossiliferous on the island, the Gault can still reward the patient collector with treasures from these muddy mid-Cretaceous seas: ammonites such as Hoplites, Hamites, Euhoplites, Anahoplites, and Dimorphoplites; belemnites including Neohibolites; bivalves such as Birostrina and Pectinucula; gastropods, including the splendidly elegant Anchura; solitary corals; fish remains, including shark teeth; scattered crinoid fragments; and crustaceans — among them the crab Notopocorystes, a name which sounds faintly like a Roman senator.
Occasional fragments of fossil wood may also be found, drifted from ancient shores and entombed in marine mud. The lovely ammonite before us comes from the Gault Clays of Folkestone.
Not all workers would split the genus Euhoplites so finely, and there is a respectable argument for viewing this beauty as a particularly robust form of E. loricatus, with Proeuhoplites regarded as a synonym of Euhoplites. Taxonomy, as ever, remains one of science’s more genteel battlegrounds.
Much of the fine knowledge surrounding these beds has been shared by collectors such as Jack Wonfor, whose collections contain many beautiful Gault ammonites.
For those wishing to delve deeper, the Palaeontological Association publication Fossils of the Gault Clay by Andrew S. Gale is available in Dinosaur Isle’s gift shop.
And there is also an excellent website maintained by Fred Clouter, filled with references, resources, and links to some of the finest books on the Gault Clay and Folkestone Fossil Beds. You can explore it here: http://www.gaultammonite.co.uk/
A tiny shell, a scrap of clay, and suddenly an ancient sea returns to life. Not bad for 2.6 centimetres of swagger.
