13.3" Fossil Ammonites With Petrified Drift Wood - Dorset, England

This is a gorgeous association of ammonite fossils and petrified wood within a concretion, collected from the Lyme Regis region of England. The largest ammonite Promicroceras planicosta) is 1.1" wide sits right at the center of the specimen. The petrified wood is just beneath the large cluster of ammonites and runs across the entire base of the specimen. One edge of the rock has been cut flat, facilitating aesthetic presentation of the fossils. A truly stunning specimen!

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.

Petrified wood is the name given to wood that has been turned into stone (fossilized) through the process of permineralization. All of the organic matter becomes replaced by minerals, while much of the original structure such as tree rings in retained. For this to happen the wood needs to be buried in an environment both low in oxygen (preventing decomposition) and with flowing, mineral-laden water. The coloration is due to the various minerals that are present during fossilization. For example red colors are due to iron compounds, greens due to copper, etc.
Promicroceras planicosta & Unidentified Wood
Lyme Regis, Dorset, England
Lower Lias, Obtusum Zone
Entire specimen 13.3 x 7.6"
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