Asteroceras obtusum (Sowerby)
The pair of aptychi are the 'doors' that lose off then entrance to the body chamber when the animal retreats into it's shell. They are made of Aragonite and rarely preserve. Here we see the lozenge shaped aptychus lodged in the entrance to the body chamber. Very unusual and rare find.
Jurassic, Upper Sinemurian, Obtusum Zone.
Black Ven, Charmouth / Lyme Regis, Dorset.
Aptychus : 1.5 x 0.8 cm.