These beautiful ammonites are an extinct group of marine mollusk that were distant relatives of the living squid and octopus. The name ‘ammonite’ was given by Pliny the Elder because of the resemblance to the ram’s horns of Ammon, the Egyptian god of life and procreation. ‘Dactylioceras’, on the other hand, comes from the Greek word for ‘finger’, describing the ribbed shell that reaches out from a centre. Widespread and diverse in Jurassic and Cretaceous periods, ammonites then died out, but have been found world wide. These beautiful ammonites date to 170 million years ago and come from North Yorkshire which at that time was considerably nearer to the equator due to continental drifting. Only one in twelve ammonites is suitable to be polished and made into these weights.
Cross-Section of Dactylioceras commune
One interesting example of the fossil Dactylioceras commune, here sliced into equatorial cross-sections and highly polished. The chambers have been filled wiuth minerals, while the final body chamber is a dark grey, as it was filled with sediment soon after the death of the animal.