6.4" Polished Nautilus and Ammonite Fossil Association - England

This is a natural nautilus and ammonite fossil association that was collected from the Lower Jurassic age Falciferum Zone near Lincolnshire, England. The nautilus is of the species Cenoceras astacoides and the ammonite is of the species Harpoceras serpentinum. The shell of the nautilus fossil has been polished, away revealing the mineral replaced chambers. The fossils have been partially exposed from the hard limestone that they were found in, creating this aesthetic specimen.

The entire specimen measures 6.4 x 5.4" and the base has been cut flat for presentation purposes. The nautilus measures 3.7" wide and the ammonite is 2.2" wide.

Ammonites were predatory mollusks that resembled a squid with a shell. These cephalopods had eyes, tentacles, and spiral shells. They are more closely related to a living octopus, though the shells resemble that of a nautilus. True ammonites appeared in the fossil record about 240 million years ago. The last lineages disappeared 65 million years ago at the end of the Cretaceous.

What an ammonite would have looked like while alive.
What an ammonite would have looked like while alive.

The shell of a Nautilus is made up of two layers. The inner layer has the iridescent shine while the outer layer provides protection from external forces. Inside the shell are septa which divide the living area of the shell into compartments and help the animal maintain balance and position in the water column.

Nautilus are "living fossils" in that species similar to this one still exist in our oceans.
Cenoceras astacoides (Nautilus) & Harpoceras serpentinum (Ammonite)
Lincolnshire, England
Falciferum Zone, Upper Lias
Entire specimen 6.4 x 5.4". Nautilus 3.7" wide
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