I’ve mentioned it before but it bears repeating: dinosaurs were my first love. Forget raindrops on roses and whiskers on kittens, fossilised trilobites and petrified wood were a few of my favourite things when growing up. This is just to provide a bit of context for the Christmas gift I bought myself last year: a slab of stone covered with the remains of ammonites.
It was my last day in the office before the holidays, and it was purely by chance that I spotted the sign for a fossil and mineral sale. I went to take a peek … and was a goner: trilobites and belemnites abounded; labradorite shimmered and sparkled like a rainbow that had been compressed so it could fit into the palm of your hand; and the ammonites … so many ammonites!
These now-extinct molluscs once ruled the ancient oceans of our planet, and are some of the most common fossils found, yet I am always amazed by their beauty. There were highly polished ones from Madagascar, others had been sectioned so you could see each individual chamber, and there were even a few that had been pyritised—the minerals in the shell replaced over time by iron pyrite instead of quartz or calcite— and turned into stunning works of metallic art.
I may have picked out one or two (or six) of these other things before fully turning my attention to some of the bigger items were on display, and that’s when I saw the slab. Ammonites covered it in layers, and wood had also been captured in the concretion. It became very easy to imagine the ammonites—believed to have been killed by a lack of oxygen in the water—being swept along with debris and tossed up on shore. Sediment quickly entombed the assemblage, protecting it from destruction and capturing a single moment in time that has survived into the present.
It has also turned the ammonites into time-travellers from the distant past, albeit ones who have taken the long way around. In the 165 million years since they set off on their journey, the planet has undergone extraordinary changes. At their start in the middle Jurassic, they would have shared the seas with ichthyosaurs and plesiosaurs, and dinosaurs continued to dominate the land (although cynodonts and mammals were slowly making inroads). Continents drifted. A meteor brought the non-theropod dinosaurs to an end, giving the mammals a chance to get a firm toehold and allowing the avian dinosaurs to develop into over 10,000 species of bird. Ice ages came and went a number of times. And a group of hairless apes set off to conquer the planet.
At £80.00, some may find the price tag for this piece of the past exorbitant. After all, it serves no ostensible purpose, and it is rather too large to be used as a paperweight. But the story it tells? Priceless.
A pyritised ammonite clearly showing suture lines on the shell. These lines get more complex over time, so it has become a useful tool for identifying the age of the ammonite and the rocks surrounding it.
The mother-of-pearl shell survives on this ammonite, providing a better idea of what these cephalopods–relatives of octopus, squid, and cuttlefish–may have looked like in life.
A few pieces from my ammonite collection. Ammonites take their name from the Egyptian god Ammon, who is represented by a ram. Those in antiquity thought the spiral looked like a ram’s horn and the name stuck.
A little bit of prehistoric wood that was caught on shore with the ammonites … and ended up in a Wiltshire quarry 165 million years later.
This is the impression an ammonite has made in the underside of the slab …
… and the surface of the slab is covered with their fossilised remains.
Not a fossil, but a piece of polished labradorite is also an incredible work of nature.
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