Out of This World II Tuesday, 18 April 2023, 4pm

928* SPINY AMMONITE Crioceras Nolani Cretaceous, Hauterivian, 129–132 million years Alpes de Haute-Provence, France 39 × 43 cm (without stand) Ammonites are an extinct group of cephalopods that were very rich in form. There are 1500 known genera of ammonites. Thanks to their variety of forms ammonites are a popular collector‘s item. Their shell – rolled up in the manner of a logarithmic spiral – recalls a snail, but this is not the case with all ammonites. The species Crioceras Nolani has a flat, spiral shell, where no coil is in contact with the other. Why the shape developed in this way is unknown. Possibly this species lived in the benthic zone at the lowest level of the sea, so there was no need for a shell suitable for swimming. The spines decorating the animal‘s shell served as protection for the ammonite, which was either sedentary or could only move slowly on the sea floor. The specimen presented here is in very fine condition, showing only restorations to the long spines. CHF 8 000 / 12 000 (€ 8 000 / 12 000) 929* FOSSIL WOOD Araucarioxylon arizonicum 225 million years Arizona, USA This fossil wood example from the southwestern US state of Arizona is of astonishing beauty. In 1988 the Arizona state legislature designated the petrified wood of Araucarioxylon arizonicum, a prehistoric conifer, as an Arizona state fossil. Arizona is famous for its vast petrified forest, part of which lies within the bounds of the Petrified Forest National Park. During the Late Triassic period, approximately 225 million years ago, Northern Arizona had a tropical climate that supported a vast forest of conifer trees. The majority of the trees were of the species Araucarioxylon arizonicum, which grew up to 200 feet (61 m) tall with a trunk up to 5 feet (1.5 m) thick. It likely would have resembled a modern pine tree. Occasionally fallen trees would become buried in sediment and volcanic ash. Due to its rapid burial and the lack of oxygen, the wood did not decay as it would if it had remained on the surface. Silica and other minerals present in the ground water seeped into the porous wood over many years. This caused the cellular structure of the wood to become crystallised and turned it into a fossil. The rainbow coloration with vibrant hues of reds, yellows and purples is typical for petrified fossils fromArizona. It is made up of almost solid quartz, like a giant crystal, and sparkles in the sunlight as if it were covered with glitter. The rainbow colours are produced by impurities in the quartz, such as iron, arbon or manganese. Purple amethyst, yellow citrine, clear quartz and smoky quartz have formed here into a wonderful piece of natural art. CHF 12 000 / 15 000 (€ 12 000 / 15 000) | 35