Diploporitans had subspherical thecae, which usually were attached to hard substrates either directly with an attachment disc at the base of their theca or with a stem and holdfast. After the death of the animal, isolated thecae were easily transported by currents over more or less consolidated sediment. We describe a case where 13 diploporitan thecae were trapped in the remains of a cephalopod with an orthoconic conch. Most of the thecae show a perfect fit and are size-sorted within the conch or siphuncle. We discuss the taphonomic processes that might have been involved in this rare kind of alignment and sorting.