Desmoceratoidea

Desmoceratoidea is an extinct superfamily of ammonites, a diverse group of cephalopod molluscs that lived in the oceans during the Mesozoic Era. This superfamily is characterized by its tightly coiled, involute shells, meaning that the whorls of the shell significantly overlap each other, often hiding the earlier whorls. The umbilicus, the central opening of the shell, is typically very small or absent. Desmoceratoidea fossils are primarily found in Cretaceous period rocks, from the Early Cretaceous to the Late Cretaceous.

The shells of desmoceratoideans often exhibit complex suture patterns, which are the lines where the internal walls (septa) of the shell meet the external shell wall. These sutures are important diagnostic features for identifying and classifying ammonite species. Economically, some species of desmoceratoideans have been used as index fossils for dating sedimentary rock layers. Their widespread distribution and relatively short geological lifespan make them valuable tools for biostratigraphy. The exact phylogenetic relationships within Desmoceratoidea are still a subject of ongoing research, but they are generally considered to be a divergent and successful lineage within the ammonite evolutionary tree.