Metoicoceras geslinianum Zone

Base: The base of the zone is immediately below the first appearance of the index species (Gale, 1995).

Top: The top of the zone is immediately above the last occurrence of the index species (Gale, 1995).

Range of index species: The zone is coincident with the total range of the index species (Gale, 1995).

Key fauna:

Brachiopoda:	Monticlarella jefferiesi
	Orbirhynchia multicostata
	O. wiesti
Bivalvia:	Entolium membranaceum
	Inoceramus pictus
	Oxytoma seminudum
	Pycnodonte vesiculare (large gryphaeate specimens)
Belemnoidea:	Praeactinocamax plenus
Ammonoidea:	Euomphaloceras septemseriatum
	Metoicoceras geslinianum
	'Sciponoceras sp. (locally abundant)
Asteroidea:	Crateraster quinqueloba

Faunal abundance & preservation: Relatively closely spaced acmes of different groups of fossils are common in the zone, and were used by Jefferies (1963) to subdivide the Plenus Marls into a series of 8 beds. Aragonite-shelled molluscs are locally common, and are preserved as moulds.

Bio-markers: The basal part of the zone contains common large, gryphaeate Pycnodonte vesiculare associated with Orbirhynchia multicostata (Jefferies, 1963). In the middle and higher parts of the zone Praeactinocamax plenus and Oxytoma seminudum occur, overlain by an acme of Orbirhynchia wiesti (Jefferies, 1963). Two acmes of Sciponoceras occur in the top of the zone, overlain by an acme of Crateraster quinqueloba (Gale, 1996).

Age: Late Cenomanian