Jurassic Ammonite & Petrified Wood Association - 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 (Asteroceras confusum) is 1.7" wide and has a bite mark from a predator. The smallest ammonites are of the species Promicroceras planicosta. The preparation of the petrified wood is excellent and is centered across the middle of the specimen. It comes with a metal/acrylic display stand.

Ammonites were predatory cephalopod mollusks that resembled squids with spiral shells. They are more closely related to living octopuses, though their shells resemble that of nautilus species. True ammonites appeared in the fossil record about 240 million years ago during the Triassic Period. The last lineages disappeared 65 million years ago at the end of the Cretaceous.

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. In this process, all of the organic matter becomes replaced by minerals, while much of the original structure, such as tree rings, is retained. For this to happen, the wood needs to be buried in an environment low in oxygen to prevent decomposition and with flowing, mineral-laden water, so minerals may replace structures. The coloration is caused by various minerals that present in that water during fossilization. For example, red colors are due to iron compounds, greens due to copper, and so on.

More about ammonites