Belemnitida

Part of speech: noun

Definitions

1. An extinct order of marine cephalopods characterized by elongated, bullet-shaped internal skeletons called rostra; important fossil group from the Mesozoic era; related to modern squids and cuttlefish
2. A classification of ancient squid-like creatures known for their distinctive hard internal structures used for identification; prevalent in fossil records from the Jurassic and Cretaceous periods; ancestors to present-day cephalopods
3. Fossil cephalopods belonging to an extinct group with streamlined, conical internal shells that contributed to marine ecosystems millions of years ago; serve as index fossils for dating Mesozoic strata; relatives of contemporary marine mollusks

Etymology: Ancient Greek "belemnon" meant a dart or javelin, from "belos," a missile. Scientists later borrowed the term as "belemnites" for fossils shaped like tapered spear points, and the order name "Belemnitida" was built from that genus using the standard ending for taxonomic groups. For centuries, people across Europe mistook these fossils for something else. They were often called "thunderstones" or "thunderbolts," on the belief that lightning had hurled them into the ground, and folk tradition sometimes kept them as protection against storms. The animals themselves were squid-like cephalopods. Their dense, bullet-shaped internal skeletons were made of calcite and survived well in sediment, which is why they are so common in Mesozoic rock. Their closest living relatives are squids and cuttlefish.

Synonyms: belemnite, extinct cephalopod