Belemnites are an extinct cephalopod that existed between the late Triassic and Late Cretaceous, related to modern cuttlefish and squid. Though not as colorful as its relative, Ammonites, Belemnites are one of the most interesting fossils. Their guard (the fossil) is a complex and fascinating structure.
Belemnitida is an extinct order of Cephalopod. As with modern cuttlefish, they had an internal structure that provided shape and buoyancy. Like squid, they had tentacles but unlike them, Belemnites had hooks on their tentacles instead of suction cups. Belemnites are the state fossil of Delaware.
Artists reconstruction of a belemnite (Youngibelus). Image by NobuTamura, Creative Commons License
When Did Belemnites Live?
Belemnites appear in the fossil record at the end of the Late Triassic Period about 234 million years ago and disappeared about the same time as the dinosaurs, about 66 million years ago.
How Big Were Belemnites?
Because the only part of most Belenites that survives is the solid end of the shell, called the guard, total size is speculative. The largest guards found belong to Megateuthis elliptica and was 24- 28 (60-70 cm) inches long. This suggests that the total length of the animal could have been as much as much as 20 feet long. The shortest guard is from the genus Neohibolites and was 1.2” (3 cm) inches.
Where Did Belemnites Live?
Belemnites were marine organisms. As a result they occupied most of the same ocean environments that modern cuttlefish and squid occupy today. Some were quite fast and mobile and probably occupied the open ocean much the same as modern squid. Others were probably more sluggish and kept to shallower areas.
What Did Belemnites Eat?
Belemnites were carnivores and probably ate any animal they could safely subdue. There is some evidence that some species of Belemnitida that traveled in large schools and swarmed prey. This would be most likely in medium to larger species. Smaller and slower moving species would have likely relied on crabs and other crustaceans much the same as modern cuttlefish.
How Did Belemnites Move?
Belemnites, like cuttlefish and squid had two ways of moving through the water. If they were moving slowly or just making small movements, they could move by oscillating the fins near the top of the mantle. If they needed to move rapidly, they had the capacity to move by pushing a jet of water out their syphon, just as squid and cuttlefish today.
What Are Belemnites Closest Living Relatives?
Belemnites were most closely related to modern cuttlefish. They probably looked a lot like squid but unlike squid, cuttlefish have an internal shell similar to the rostrum of Belemnites.
What Part Of The Belemnite Is Fossilized?
The most common part of the Belemnite in the fossil record is the guard and the hooks of the tentacles. This guard is the solid end of the rostrum (inner shell). The hollow end of the rostrum is often destroyed before it can be fossilized. Most soft tissue does not survive fossilization, but there are a few instances where the impression of the soft tissue is preserved. In a few specimens a structure that appeared to be an ink sack has been found.
Very rare Belemnite fossil from Posidonia Shale of Germany with soft bodied preservation. On display at the Museum am Löwentor, Stuttgart in Germany. Creative Commons License
Washington state has now joined over a dozen other states to put in place “shelter in place” or “stay at home” orders. While we agree this is the correct course of action, it will have a substantial impact on our business. It effectively shuts down much of our company for several weeks.
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