page_title: Belemnitida
section_title: Research history
hierarchical_section_title: Belemnitida / Taxonomy / Research history
caption_attribution_description: English: Fossil of Hibolites semisulcatus
context_page_description: Belemnitida is an extinct order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous. Unlike squid, belemnites had an internal skeleton that made up the cone. The parts are, from the arms-most to the tip: the tongue-shaped pro-ostracum, the conical phragmocone, and the pointy guard. The calcitic guard is the most common belemnite remain. Belemnites, in life, are thought to have had 10 hooked arms and a pair of fins on the guard. The chitinous hooks were usually no bigger than 5 mm, though a belemnite could have had between 100 and 800 hooks in total, using them to stab and hold onto prey.
  Belemnites were an important food source for many Mesozoic marine creatures, both the adults and the planktonic juveniles, and likely played an important role in restructuring marine ecosystems after the Triassic–Jurassic extinction event. They may have laid between 100 and 1,000 eggs. Some species may have been adapted to speed and swam in the turbulent open ocean, whereas others resided in the calmer littoral zone and fed off the seafloor. The largest belemnite known, Megateuthis elliptica, had guards of 60 to 70 cm.
context_section_description: The first mention of belemnites in writing comes from the Greek philosopher Theophrastus, who lived in the 4th and 3rd century BCE, in his book De Animalibus Quæ Dicuntur Invidere who described it as lyngurium, lynx urine which had been buried and solidified. Pliny the Elder, in the first century CE, did not believe in lyngurium, and called the gemstone a belemnite for the first time—though not recognizing it as a fossil. The name is from Ancient Greek βέλεμνον bélemnon meaning dart for the guard's shape. Subsequent authors either considered it to be lyngurium or amber. The first mention of a belemnite representing a fossil was made in 1546 by German mineralogist Georgius Agricola, and subsequent authors gave several hypotheses to its nature in life, including them being shellfish, sea urchin spines, sea cucumbers, coral polyps, or some internal shell.
  In 1823, English naturalist John Samuel Miller classified belemnites as cephalopods, comparing the newly discovered phragmocone remains to that of a nautilus, and concluding a resemblance to Sepia cuttlefish. He also erected the genus Belemnites with 11 species. This classification was confirmed when the first impressions of belemnite soft body anatomy were described by English paleontologist Richard Owen in 1844. In 1895, German paleontologist Karl Alfred Ritter von Zittel organized the clade Belemnoidea and included the families Belemnitidae, Asteroconites, and Xiphoteuthis.
  The guard—also known as the rostrum, scabbard, gaine, and sheath—is the part of the animal most likely to be fossilized. Guards are difficult to distinguish at the species level, and, consequently, synonyms are common and inflate the group's apparent diversity. Preserved hooks can be used to distinguish belemnite species as each species has unique hook shapes. However, scolecodont segmented worm fossils have been mistaken for belemnite hooks and vice versa. Preserved fossil guards are used to measure the ancient isotopic signature of the waters the individual inhabited in life, which gives information on the climate, habitat, and the carbon cycle.
caption: Hibolites from the early Cretaceous at the State Museum of Natural History Stuttgart
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