Harpoceras exaratum (Young & Bird)

Scale bar = 5cm

Description

Lower Jurassic, Upper Lias (incl. Cotteswold & Midford Sands)
Ilminster
Somerset
England
M1179
Description:

Harpoceras exaratum is a zone fossil, that is a fossil that is used to define a certain geological time span. Ammonites, an extinct order of free swimming predatory cephalopods, make excellent zone fossils as they are geographically wide spread, common in the fossil record and evolved quickly and so are only found for limited geological time scales. This fossil defines a sub-Zone within the larger time frame of the Harpoceras falciferum Zone, Lower Jurassic (Upper Lias)(also in this image M1181).
Moore, C.

Classification

Mollusca
Visceroconcha
Cephalopoda
Ammonoidea
Ammonoidea order
Ammonoidea family
Harpoceras
exaratum