New findings of rhynchaptychus-type ammonoid jaws

Ammonoids throughout their history had well-developed jaws of several types. One of these is the rhynchaptychus type, which is characterized by the presence in both jaws, the upper and lower, of sharp calcitic elements: rhyncholites and conchorhynchs, respectively. For a long time, rhynchaptychus-type jaws were only known from the Upper Cretaceous of Japan and Sakhalin, but last year they were described from the Middle Jurassic of Dagestan. Here we describe a large (more than 7 cm long) ammonoid lower jaw from the Middle Aptian of Dagestan, which contains a calcitic conchorhynch. Moreover, four ammonoid lower jaws with conchorhynchs were found in the Lower Cenomanian of the Crimea.