Macroconchs is a paleobiological term introduced by J.Callomon. This term denotes ammonites which reached maturity at a relatively large size. Macroconchs also have other distinctive features: a lack of adult aperture modifications on the final apertural edge (lappets, long ventral rostrum), simplification and often smoothing of sculpture on the terminal body chamber, changing of coiling angle on the last whorl. Most paleontologists believe that macroconchs are shells of female ammonites, whereas microconchs are male shells. The same type of sexual dimorphism is present in modern octopods which belong to Argonautidae family. The large size of female ammonite shells is likely related to the production of large numbers of eggs or even brooding eggs inside the body chamber (ovoviviparity). At the same time the smallest macroconchs are often smaller than the largest microconchs (probably due to the fact that the fast-growing cephalopods reach maturity at different sizes, depending on the ambient temperature).

The text was added and/or edited by: Alex