Early Scientific Illustration of Orthocerata
Ca. 1860's / 1880's
 
Orthocerata are extinct marine animals that belong to the phylum Mollusca and the class Cephalopoda. They lived during the Paleozoic era, which lasted from 541 to 252 million years ago. Orthocerata are one of the earliest known cephalopods and are considered to be the ancestors of modern squid, octopuses, and nautiluses.
 
The name Orthocerata comes from the Greek words "ortho," meaning straight, and "keras," meaning horn, referring to the long, straight, conical shells that these creatures possessed. These shells were composed of calcium carbonate and ranged in size from a few centimeters to over six meters in length. The shell had a series of internal chambers that the orthoceratids used to control their buoyancy and movement through the water.
 
Orthocerata were predators, and their long tentacles were equipped with suction cups and sharp hooks for grasping and capturing prey. They likely fed on small fish, crustaceans, and other cephalopods.
 
Orthocerata were widespread during the Paleozoic era, and their fossils have been found in rocks all over the world. These fossils provide valuable information about the evolution and diversity of early cephalopods and the marine ecosystems of the time.