An overview of the Albian Ammonoidea of Kent, UK
Adapted from the systematic account of the Ammonoidea in the 1966 Geol. Soc. Memoire on the Geology of the country around Canterbury and Folkestone
The richness of the ammonite fauna in the English Albian is due in part to favourable conditions of preservation but also reflects a world-wide burst of evolutionary activity that took place in the group towards the end of the Lower Cretaceous. With few exceptions Albian ammonites belong to the "Trachyostraca", the highly ornamented types that are believed to have flourished in the shelf seas, and nearly all of these belong to two superfamilies (Hoplitaceae and Acanthocerataceae) within the suborder Ammonitida and the superfamily Turrilitaceae within the suborder Ancyloceratida.
The Hoplitaceae takes in Pseudosonneratia, Protohoplites and Otohoplites occurring in the mammillatum Zone of the Folkestone Beds, the ventrally grooved ammonites Hoplites, Euhoplites, Anahoplites and Dimorphoplites, which dominate the Lower Gault, and Epihoplites, Callihoplites and the rare Discohoplites, which characterise the Upper Gault. Also included among the Hoplitids are Lepthoplites, Pleurohoplites and Arraphoceras which occur sparsely in the highest bed of the Gault and have a raised siphonal line foreshadowing the Cenomanian keeled family Schloenbachiidae.
Ammonites with a keel at some stage of growth or with a median row of nodes on the venter belong to the Acanthocerataceae. Hysteroceras, Prohysteroceras, Mortoniceras and Dipoloceras are typical keeled genera; Neophlycticeras and Protissotia, with cockscomb venter are rather scarce. Although represented in the Lower Gault by Mojsisovicsia, Diploceroides, Dipoloceras and rare Eubrancoceras and Oxytropidoceras, this superfamily did not become important until the base of the Upper Gault, after which it gained supremacy over the Hoplitaceae.
The Turrilitaceae comprises heteromorphs or abnormally coiled types such as Protanisoceras, Prohelicoceras, Anisoceras, Idiohamites, Hamites, Proturrilitoides and Pseudhelicoceras. The Douvilleicerataceae is represented in the Albian by Douvilleiceras which flourishes in the mammillatum Zone and occurs sparsely in the lowermost Gault Clay. The Ancylocerataceae is represented in the Upper Gault by the micromorph ammonite Ptychoceras adpressum (J. Sowerby) and the Scaphitaceae by the tiny Eoscaphites. Except for the Desmoceratid Beudanticeras, which is common in the mammillatum Zone and occurs frequently in the early beds of the Upper Gault, the "Leiostraca", or smooth ammonites are known only by a few chance finds of Hypophylloceras, Tetragonites, Pictetia, Desmoceras, Puzosia and Uhligella. These ammonites are thought to have preferred open waters and to have had their European centre of dispersal in the Mediterranean region.
The Placenticerataceae are another exotic element in the Gault; this superfamily is represented by isolated finds of the Engonoceratid Engonoceras iris Spath in the dentatus Zone of the Lower Gault and by the Placenticeratid Hengestites applanatus Casey in the varicosum Subzone of the Upper Gault. The Engonoceratidae, with their curiously modified "pseudoceratitic" suture-lines, characterize Albian deposits of equatorial regions and seldom strayed into the northern waters where Hoplitids abounded.
A short-term penetration into the Gault Hoplitid province by the Haplocerataceae is indicated by the occurrence of the primitive Aconeceratid micromorph ammonite Falciferella milbournei Casey in the intermedius Subzone of the Lower Gault. That the Gault sea was open to immigrants from the north was proved by the discovery in cristatum Subzone of the Upper Gault by Raymond Casey at Folkestone of the Canadian genus Gastroplites, a member of an Arctic branch of the Hoplitidae.


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