Psiloceras planorbis (Sowerby, 1824)
Hettangian Stage of the Jurassic Period (201-199 million years old)
A naturally iridescent shell showing nice neon colors including blues, greens and deep reds. This iridescence is the natural result of more than a dozen minerals replacing the shell and forming together over millions of years.
Unlike most earlier ammonites, which had complex shell shapes and ornamentation, Psiloceras had a smooth shell.
Something else to consider about this amazing group, all Ammonites, with the sole exemption of the genus Psiloceras were wiped out at the Triassic–Jurassic extinction event (201.3 million years ago). Hence all ammonites that lived during the Jurassic and Cretaceous are descendants of the Psiloceras!