Aptychus of an ammonite

Scale bar = 5cm

Description

Lower Jurassic, Upper Lias (incl. Cotteswold & Midford Sands)
Ilminster
Somerset
England
M1213
Description:

An aptychus (plueral aptychi) is part of the jaw apparatus of an ammonite. In the past the interpreted function of this structure was controversial and some interpreted the aptychi as an operculum, a guard for closing the ammonites body aperture, this is no longer a common interpretation (also in this photo M1215).
Moore, C.

Classification

Mollusca
Visceroconcha
Cephalopoda
Ammonoidea
Ammonoidea order
Ammonoidea family
Aptychus
sp.