A gift from the sea

If your idea of fossils is dull, dusty, old bones, a dazzling new specimen on display in the 77th Street Grand Gallery at the American Museum of Natural History is sure to challenge that notion. The fossilized shell of an ammonite that lived approximately 80 million years ago is alive with color, shimmering with orange, yellow, purple, red, and green like psychedelic mother-of-pearl.

The two-foot-diameter fossil is a large and particularly rare example of a marine cephalopod that was once one of the most common invertebrates in the ocean. They went extinct around 65 million years ago, after a massive asteroid impact wiped out nearly half of all living species, including most of the dinosaurs, at the end of the Cretaceous Period.

The name ammonite comes from the Egyptian god Ammon, whose ram-like horns resemble the spirals in the sea creature's shell. The shape of the shell is reminiscent of today's chambered nautilus, but the ammonite's nearest living relative is the modern squid.

High temperatures and pressures acting on this shell for millions of years preserved its iridescent nacreous layers. Ammonite fossils that exhibit this characteristic are known as ammolites, and share the spotlight with amber and pearl as one of only three gemstones produced by living organisms.

Scientists greatly value ammonites, colorful or not, as clues to the relative age of the rocks in which they are found, because different species of ammonites lived during different time periods. Their presence also indicates the location of ancient seas, such as the Western Interior Seaway in the middle of North America where this ammonite lived.

The fossil was unearthed by ammolite miners near Lethbridge in Alberta, Canada, and donated to the Museum by Korite International and Canada Fossils Ltd.