RHYNCHOLITES AND CONCHORHYNCHS (CEPHALOPOD JAW ELEMENTS) FROM THE UPPER CRETACEOUS MOUNT LAUREL FORMATION OF DELAWARE

Rhyncholites and conchorhynchs are the calcitic elements of upper and lower jaws of cephalopods, respectively. Rhyncholites and conchorhynchs occur in relatively high abundance and are widely distributed, with a long geological range, extending from the Triassic to the Eocene. The morphology of rhyncholites and conchorhynchs is comparable to those in modern Nautilus. Therefore, they are usually attributed to fossil nautiloids with some exceptions. They are often found in isolation and, thus, identifying the taxon that rhyncholites and conchorhynchs are associated with is difficult. As such, it is a common practice for paleontologists to apply the concept of parataxonomy when documenting and classifying fossil rhyncholites and conchorhynchs. While rhyncholites and conchorhynchs are relatively common in Europe, there are only a few reports from North America. Here, we document rhyncholites and conchorhynchs from the Upper Cretaceous Mount Laurel Formation in Delaware. We also carry out detailed morphometrics to discuss the taxonomy.