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November 23, 2016, 05:20 PM

Dreamy ammonites wiped out by asteroid, free to $100k

By Thornton Kay

Asteroceras ammonite from Lyme Regis with traces of ammonitic sutures [photo TK Salvo

Iridescent nacre ammonite [photo Sotheby's
Ammonitic sutures on a large ammonite
Ammonite varieties by Haeckel [cc wikipedia

West Sussex, UK - Ammonites were named after the ram's horns of the god Ammon by Pliny the Elder - the adventurous Greek naturalist who died during the eruption of Vesuvius, famously saying that fortune favoured the brave. He wrote Horn of Ammon is one of the most sacred stones of Ethiopia, has a golden yellow colour and is shaped like a ram's horn. The stone ensures without fail that dreams will come true. In medieval England ammonite fossils had magical powers and were known as snakestones. According to legend the Saxon abbess St Hilda (614-680) of Whitby turned snakes into stone ammonites.

The largest example of more than 2,000 varieties of ammonite, in Munster Natural History museum, is over 8ft in diameter, and the smallest are less than a millimetre across. They are found in hotspots around the world, one of them being the Blue Lias beds near Lyme Regis explored in the early 1800s by a local girl, who became the great paleontologist and dealer Mary Anning (1799-1847). Denied recognition in her lifetime because she was a woman, Anning is known by the English tongue twister - she sells seashells down by the seashore. In 2010 the Royal Society finally included Anning in a list of the ten British women who have most influenced the history of science.

Summers Place auctions is the UK fossil specialist with natural history sales which invariably include ammonites, its latest sale being no exception, although the top lot in this week's sale - featured far and wide by the mainstream press - was a dodo skeleton which sold for 346,000 including buyer's premium.

Size is of the essence when it comes to valuing ammonite fossils, although surface quality can also be important. During the clean up process, after they have been dug out of the softer bedrock, an ammonite fossil can be 'enhanced' by having its whorls recut towards the centre of the spiral. Some ammonites have leaf-like surface markings known as ammonitic sutures which also increase value.

Sotheby's and Christie's have sold top-end ammonites, those which have a natural iridescent nacre or mother-of-pearl known as ammolite (see the ammonite queen video below). These shells tend to be compressed and flattened. Fantastic less flattened specimens of up to 40cm diameter and fairly complete, with darker purple iridescence, can reach $100,000 or more at auction.

The spiral fossil shells of this cephalopod mollusc are mainly used by geologists as an index fossil to date rock strata, but not much seems to be known about the creature that lived inside because no-one has yet found fossils of any associated soft tissue. Although superficially similar to the modern deep-sea nautilus, apparently the ancient ammonite had more in common with a squid, cuttlefish or octopus.

Ammonites were carnivores which first appeared in the Devonian period around 400m years ago, and swam about in its warm seas, probably controlling flotation by filling their chambers with air or water, and living midwater feeding on passing fish, until 66m years ago at the end of the Cretaceous era when an asteroid landed in Mexico and caused the K-Pg mass extinction.

The resulting climatic mayhem not only annihilated the ammonites but also three quarters of the planet's living species including the dinosaurs.

Summers Place Auctions

YouTube: Ammonite queen and freaky friend
YouTube: Beadblasting an ammonite

Story Type:  Feature

ID: 97839

Date Modified: November 24, 2016, 11:26 AM

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