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Marine Fossils and their Living Relatives


CEPHALOPODS: Octopus, Squid, and Nautilus 
Fossil: Nautiloid 
Aturia angustata

This Aturia is a long-lived species that has been found in rocks 30 to 15 million years old in western Washington. Nautiloids are squid-like animals with coiled external shells and were once common around the world but now only a few species live in the South Pacific.

The nautiloid shell is separated into chambers by cross-walls, called "septa," with a tube running down the middle and connecting of all of them to the living chamber— the last one. In life, soft tissue covers this septum, and the animal can pump gases in and out of the chambers to change its buoyancy—thus it can go up and down in the water column to look for food or to hide from predators.

Most Aturia angustata specimens have been found in rocks that indicate the sediment was deposited off shore at water depths of more than 200 meters. These nautiloids apparently lived as Nautilus does today by remaining in the water column and staying away from the shore.

For more scientific information, see the Tree of Life pages for cephalopods and for living Nautilus.

Aturia specimen
This Aturia specimen is a fossil nautiloid.
Photo by Ron Eng

giant octopus
This charismatic cephalopod, the giant octopus (Enteroctopus dolfleini), is the mascot of the Port Townsend Marine Science Center.
Art by Diane Gussett/PTMSC

Giant octopus 
Enteroctopus dofleini 

Octopus, squid, and nautilus are living members of the molluscan group called cephalopods, characterized by having tentacles. Fossil cephalopods include the very large and diverse group of shelled cephalopods called ammonoids, which became extinct 65 million years ago along with the dinosaurs. However, another group of shelled cephalopods, the nautiloids, survived this mass extinction, and although they were not very numerous or diverse, they continued to live off the west coast of North America until about 15 million years ago. Today nautilus species only live in the southeastern Pacific, deep within tropical seas.

The giant octopus Enteroctopus dofleini is the world's largest species of octopus. Adults generally reach lengths of 7 meters from one arm-tip to another and weigh 60–80 kilograms, but museum records from California show one that measured over 9 meters and weighed 180 kilograms. They live along the shallow coast of the northern Pacific Ocean and are most common close to the shore in depths of approximately 5 meters of water, where they hunt for crabs, shrimp, snails, and clams. They can change the color of their skin rapidly to blend in with the background: seaweed, kelp fronds, sand, or rocks.

Enteroctopus dofleini live for around 4 years. The female lays 20,000 to 100,000 eggs over a few days, then she stays to tend to the eggs. She continues to clean and care for the eggs until they hatch over about a 4-month period. During this time she doesn't feed, and when the juveniles swim away she dies.