Belemnite Phragmocone & part of the Pro-Ostracum, Germany 1.JPG
Belemnite Phragmocone and part of the Pro-Ostracum
Jurassic Period (201.3-145 million years ago)
Belemnitida (or belemnites) is an extinct order of cephalopods which existed during the Mesozoic era, from the Hettangian age of the Lower Jurassic to the Maastrichtian age of the Upper Cretaceous. The belemnite is the state fossil of Delaware. Belemnites studded with small inward-curving hooks used for grasping prey. However, they lacked the pair of specialized tentacles present in modern squid. Belemnites (and other belemnoids) were distinct from modern squid by possessing hard internal skeletons. The internal skeleton was composed of the guard or rostrum (plural: rostra), a heavy solid structure at the posterior of the animals. The rostrum was usually bullet-shaped and projects prominently backward, but in the suborder Belemnotheutina, it was only present as a thin layer. While the inherited camerate portion of the internal skeleton (see below) was of aragonite, the evolutionarily novel rostrum was composed of calcite. Due to its more geologically stable calcite constitution, the rostrum is often the only remains of the animals preserved, often in very large numbers in a given area.
Class: Cephalopoda Clade:†Belemnoidea