Belemnites are a group of fossil cephalopods. They existed from the Lower Carboniferous to the end of the Cretaceous. From about 358 to 66 million years ago. Their skeletal elements, the rostrums, are also called ┬┤thunderbolts` or devil's fingers`.
The belemnites resembled today's squid in appearance, had 10 tentacles and an ink sac. They had hooks rather than suction cups on their tentacles.

The belemnitic rostrum is mostly survived as a fossil. In the frequently occurring special case of an epirostral addition, ortho- and epirostrum are distinguished; both together are called holorostrum. In general, it is the orthorostrum that characterizes and is found in most species. Even when the art forms an epirostrum, it is often lost because of the vulnerable transition site, and both parts are found isolated from each other. For these reasons, it has become customary to refer to orthorostrums in general as rostrums.

For collectors, most identification clues come from the shape and surface features of the rostrums.

Common species in Holzmaden:

is a genus of belemnite an extinct group of cephalopods. The rostrum is very slender, elongated, rod-shaped, cylindrical and tapering.

Acrocoelites is a genus of belemnite, an extinct group of cephalopods. Mostly medium sized, ca 60-100 mm long, long, slender to strong and with more or less sharp tip.

Passaloteuthis is a type of belemnite an extinct group of cephalopods. Passaloteuthis is notable for being associated with a pair of mega-hooks known as onychites. These hooks are tentatively interpreted as male-specific features, though their exact function is still unknown.