Back in the early 1970s this fossil was found in a heap of clay spoil when a new sewer was being dug for a housing estate close to Northampton. It has sat in a box in a drawer ever since but has always fascinated me as it is flexible rather than rigid. The individual component parts seem to have formed separately but are articulated to each other. The first piece detaches as the pictures show. My father had it looked at about 40 years ago and the note with the fossil shows it as an Amoeboceras? Please could someone advise if the articulated nature of this fossil is fairly common or is this unusual? Thanks in advance.
Amoeboceras is entirely feasible; it is of the right age and superficial appearance.
However, I don't have enough detailed knowledge to confirm that Amoeboceras is the correct ID.
Amoeboceras is an ammonite. Ammonites have coiled shells comprised of chambers (camerae), each of which is separated from the next by a thin wall (septum). As the animal grew, it successively added one camera after another, but it only lived in the most recent one (though it maintained a siphuncle connecting the old chambers so it could manage its byouancy). One of the features of ammonites (as opposed to other ammoids) is the complex wavy shape of the septa; by corollary the camerae are also complex in shape.
Ordinarily, the whole shell remains entire as a fossil. With your specimen, however, it seems that the fossilization process has resulted in your fossil being a jigsaw of loose camerae. In my experience, that is unusual. Nice.
Thanks very much Mike, I appreciate the reference links as well. By chance I also have a virtually identical ammonite to the one shown in your reference link to the Bedford Museum collection that was found in the same spoil as the articulated fossil. I very much appreciate your reply.