Large Polished Goniatite

Goniatites are Ammonoids with a distinctive goniotitic zig-zag pattern in the sutures that mark the spiraling growth of the shell. The extinct ammonite that decended from Nautiloids is an example of the remarkable symmetry often found in nature. Mineral exchange over the eons can create an amazing array of contrasting colors and the beautiful natural display you see here. Ammonites were Cephalopods sharing a common ancestor with the squid and octopus. The ammonites that appeared in the Devonian became very diverse and widespread in the Paleozoic and Mesazoic before going extinct along with the dinosaurs at the end of the Cretaceous period. The goniatites lived early in the Devonian period, some 400 million years ago, and became extinct during the Permian period.

The pictures tell the story of this large, beautifully polished display fossil exhibiting a mixture of earth-tones. The thin walls between the internal chambers of the shell are called the septa, and as the goniatite grew it would move its body forward in the shell secreting septa behind it, thereby adding new chambers to the shell. The sutures (or suture lines) are visible as a series of narrow, wavy lines on the surface of the shell. The sutures appear where each septa contacts the wall of the outer shell..