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ORTHOCERAS FOSSILS FOR SALE
What Is Orthoceras?
Orthoceras is genus of extinct cephalopods related to modern squids, octopuses, and nautili. They are characterized by long, straight, conical shells; tentacles; and the ability to use jets of water for locomotion.
On a technical level most of the fossils people refer to as Orthoceras are not actually in the genus Orthoceras, but in other closely related genus'. For example the Devonian deposits in Morocco that produce most of the polished Orthoceras fossils have several genus including Michelinoceras and Arionoceras found in association. The look nearly identical so unless you are one of the world's leading experts on fossil cephalopods, good luck telling them apart.
What Did Orthoceras Look Like?
Othoceras species had long conical shells covered with fine lines called lirae. The shells are made up of increasingly large rings. Inside each ring is a septa, or chamber: These are where the animals lived as they grew. The large open end of the shell would have been the current living chamber and contained the animal itself: this is very similar to how modern nautili and even ancient ammonites lived. Othroceras had tentacles, a squid-like beak, and large eyes. Their original colors are unknown.
Artists rendering of an Orthoceras. Image by Nobu Tamura Creative Commons License
When Did Orthoceras First Appear?
Orthoceras first appeared in the early Ordovician Period, about 488 million years ago. Their diversity peaked in the Late Ordivician through the Devonian Period before the genus finally dwindled in the Triassic.
When Did Orthoceras Go Extinct?
Orthoceras disappeared from the fossil record during the lower Triassic Period, about 200 million years ago.
How Did Orthoceras Move?
Orthoceras had two modes of locomotion. As a bottom-dwelling organism, they likely crawled across the bottom using tentacles like a modern octopus or cuttlefish. To move around in the water column, they used forced water jet propulsion. They would take in water and force it out through siphons at high speed, thus propelling themselves in the opposite direction. This is the same way modern cuttlefish, squids, and octopuses move quickly underwater. On the bottom, Orthoceras held their shells horizontally. Both on the bottom and in the water column, they could maintain their positions by filling empty chambers in their shells with air or water to adjust buoyancy.
Why Are Orthoceras Fossils So Common?
While they lived, Orthoceras was an extremely common animal that probably made up the majority of the biomass in the world's oceans. They also had a hard shells that easily fossilized.
How Big Was Orthoceras?
Orthocerida were one of the dominant orders of their time, and as a result ranged widely in size. The smallest were less than an inch (2.5 cm) long, and one species grew to 14 feet (4.2 meters)!
Where Did Orthoceras Live?
Orthoceras were bottom-dwelling organisms that occupied deep ocean ecosystems. No specific depth information is available, but it is thought that they occupied the zone below available sunlight.
What Did Orthoceras Eat?
Orthoceras probably ate anything they could safely subdue, including fish, invertebrates, and even smaller Orthocerida species.
Does Orthoceras Have Any Living Relatives?
Orthoceras' closest living relatives are modern squid, cuttlefish, and octopus.
What Is The Difference Between Orthoceras And Baculites?
There is ongoing confusion about what is an Orthoceras and what is a baculite. Orthocerida existed from the Ordovician until the Triassic. Baculites lived during the Late Cretaceous. Both had straight shells, but the patterns developed between the inner and outer shells (sutures) are much simpler in Orthocerida and much more elaborate in Baculites.