Ptychodus marginalis-England

Taxa: Ptychodus marginalis

Geology: Kent Chalk

Age: Cretaceous

Locality: England

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Ptychodus marginalis

Ptychodus marginalis was a large, extinct Cretaceous shark known for its broad, flattened teeth arranged in pavement-like plates, specialized for crushing hard-shelled prey such as mollusks. Its teeth had parallel, slightly wavy ridges that curved anteriorly and interconnected, distinguishing it from other Ptychodus species. Fossils of P. marginalis are found in Middle Cenomanian to Middle Turonian deposits, notably in the English Chalk. This shark likely reached several meters in length and played a specialized ecological role as a shell-crusher in ancient marine environments.

Kent Chalk

The Kent Chalk is a thick Upper Cretaceous limestone sequence forming iconic landscapes like the North Downs and the White Cliffs of Dover. It is divided into three main layers: a pure white, flinty upper layer; a compact, occasionally hard middle layer; and a lower layer, all together reaching up to about 500 feet thick in places. The chalk was deposited in a shallow sea around 65–100 million years ago and is often interbedded with flint and marl. It is well exposed in sea cliffs and is important for its geological, hydrogeological, and historical significance in Kent.