A downward spiral

Ammonites are often the first thing people thing of when fossils are mentioned. Their spiral-shelled form is iconic in palaeontology; memorably beautiful, appealing to artists and mathematicians alike.

They appeared in the Devonian, and died out alongside the dinosaurs during the extinction event at the end of the Cretaceous, 65 million years ago. Meantime, they survived two big extinctions, at the ends of both the Permian and Triassic. Tough cookies.

They are incredibly useful stratigraphic markers, providing clues as to the age of the rock layers they are found in, and by extension, helping show relationships between bodies of rock in different parts of the world.

The name ammonite comes from the Egyptian god Amun, who was, towards the latter part of his career as a deity, depicted as having the head of a ram. Rams, as most of you will know, have nice, tightly coiled spiral horns, and the resemblance to ammonites is obvious. See how convoluted I've managed to make this explanation? Pliny the Elder named the fossils he was finding after the horns of Amun. Pliny the Younger named them poo-stones (in Greek) and got a clip round the ear.

Going off at a bit of a tangent for a second, here, I love how the ancient Egyptians gave their gods animal heads. Real character. Maybe there were some that didn't get much press that had other animal body parts. A god with the legs of a chicken? The arms of a bear?

It is often assumed that the closest living relative of ammonites is the nautilus, and it's easy to see why. Most recent study, though, suggests that the octopus may be the true relative. Now a god with an octopus for a head - there's a winner. Don't think Cthulhu counts...

There's a fair bit of mythology attached to the ammonite. St Hilda of Whitby in the middle 600s AD was supposed to have killed all of the snakes in the area by decapitating them with her whip - the ammonites found around the Yorkshire coast were assumed to be the remains. Local craftsmen have carved heads on them to form lucky snakestones for centuries. In 5th Century India, ammonites were regarded as the embodiment of a god, 17th Century Germans considered them a charm against witchcraft, and many North American plains tribes carried them for good luck, too.

For me, though, they are simply one of the most appealing forms in nature. There's something magical about the spiral.

All the pretty fishes

The Green River Formation of Southwest Wyoming is has to be one of the favourite fossil localities of every fossil dealer on the planet. The many layers of micrite - muddy limestone - that compose the formation contain fossil fish of exquisite detail and in numbers that would make your eyes bulge from your head, pop and dribble down the front of your shirt.

And not just fish - bats, birds, reptiles and even a small horse have been found. These are rare, though, and fetch tidy sums. The beauty of the site is that it offers so much high quality material that there is sufficient to supply the academics with as much as they could possibly need whilst also providing a fantastic commercial line for the fossil trade.

The site(s) have been very well studied over the years and a great deal is known about the geological history. The rocks were laid down as a series of lakes, shifiting over time from about 58 million years ago for perhaps 15 million years. By far the most common fish found is the Knightia, below left, a relative of the modern herring, followed by Diplomystus, above right. Most of the fossil-bearing layers date to around the 50 million mark. There are 10 or 11 private quarries, many offering digging expeditions, and also a National Park, where some of the rarer material is carefully protected.

The amount and quality of the fossil material in the Green River Formation allows great insight into the environment of the area at the time. Leaves, seeds and even flowers from a number of plants can be found, and a good idea of the fauna is preserved within the rock - a snapshot of the area's wildlife.

Wyoming weather permits only a few months fossil hunting each year and the professional diggers make the most of it. They have to strike a delicate balance between keeping their potential finds intact whilst also shifting tons of rock about with heavy machinery. The more valuable finds are often from deposits from the edges of the lakes - mammals, birds, reptiles - and this material is also the hardest to access.

I've been invited to go digging a number of times. I'd love to go, but it would be difficult to justify financially, as I see the dealers at the Tucson show and buy from them there. One day, though.

Bright sparks

Yesterday was curtailed by a power cut. The joy often experienced by those excused work by elements beyond their control is not necessarily shared by small traders.

I had some customers in, and they stuck around for a while, as they had some questions about ammonite hunting. I showed them how it was usually possible to see the edge of the shell protruding from a nodule, and where the collector would then place the chisel to try to open it. By torchlight.

Yet again there are roadworks outside the shop - not sure why this time. On this occasion they drilled through an electricity cable, cutting off power to the bookshop next door. When my lights went off, I went next door to find that Mike had already been without electricity for a while and had done the sensible thing. Headed to the pub. I followed suit.

It can be exasperating, losing trade as a result of the ineptitude of others, especially when it's such a frequent occurrence.

Got to learn to stop griping about this stuff - back to geology next time.

Nesting

Yesterday marked the 200th birthday of Charles Darwin and I had an omelette for tea. Okay, so there's not really a direct link, but on the same day I saw an online poll asking the age-old question - 'Which came first - the chicken or the egg?'

There is no reason to be discussing this any more, as various beasties were laying eggs long before the chicken crossed the road. Dinosaur shell material and complete eggs from a number of sources have been on the commercial market for a while. Eggs from localities in Hunan and Mongolia were relatively common a few years ago, but Chinese legislature has made the exporting of the material illegal and supplies already outside of the country are beginning to dwindle. Shell from the Patagonian sauropod Saltasaurus was easy to source until another recent law change, but complete eggs were always much less available. Other shell sources included a small French locality and I think a Spanish one, but I haven't seen anything from there for a while.

The little theropod Oviraptor got its name from a famous misunderstanding. A find from a Mongolian site showed the remains of the dinosaur over a clutch of what was assumed to be ceratopsian eggs and it was thought the raptor had died getting some lunch. The name means 'egg thief'. A long time later further finds and new preparatory techniques showed the eggs to be those of the raptor and the maligned dinosaur had been nesting rather than pinching the eggs.
A prehistoric mis-trial.

The wait

After locking down the lids on my crates on the 5th of February, I now have to wait until the first week of April to actually see what I've bought again. It's a long and frustrating wait. All the British dealers and many of the other Europeans group together to share containers.

The containers arrive towards the end of the show, and once loaded are taken by road to Los Angeles. From there they go by rail to Houston, and from there by ship to Bristol. Then comes the usual customs hold up, which can take as long as two weeks, before the containers are unloaded and the individual crates go their separate ways.

This year will be the first with nice shiny plastic crates. It was always a chore to build up the wooden ones in the hot sun, and I was very glad not to have that waiting for me this year. As it turned out, I ended up building up two crates for other people, but at least mine were easy...

I'll at least benefit at this end. It was a bit of a scramble to take apart the wooden ones on the pavement outside the shop, and the new ones will make it a lot easier.

Elements

This morning, the wind blew my buttered muffin onto the ground. But that's okay.

Another postcard

All done bar the baking here in Tucson. Lids on the crates are locked down, paperwork is all done. Now I have a little time to get some heatstroke. 

I never remember how to translate farenheit to celcius, but it's in the 80s now. Hot enough to be difficult walking around, sitting, talking etc. I should go around with the camera for a while, but it seems like too much hard work.

The hotel I stay in, along with a lot of the dealers I know, is not the most exciting place. We're bordered on one side by the freeway, another by a building site, another by a dust bowl of a dry river, and finally by a Denny's diner and a petrol station. Perfect. Today Denny's had the weird idea of serving free breakfast from 6 until 2pm. Which meant massive queues for 8 hours, and a huge turnout of Tucson's many interesting characters. And a few police cars. 

A postcard

It's Sunday morning in Tucson. Two busy buying days behind me now, and a day to slow down a little and take stock. I run around picking out lots of stuff, then often have to wait a couple of days (or more) to find out exactly what I've spent. Which can be a problem. More than once I've found myself short of a fair bit of cash.

So - today I'll try to round up the various piles of fossils sitting in hotel rooms, tents and cars around the city. And put them in a big plastic crate. I've bought two collapsable shipping crates this year - will be a big help. I used to have to build up wooden one each time, and dissemble them on the pavement outside the shop. A real pain sometimes, and though I got it down to a reasonably quick time, it was still not something to look forward to on a very warm day.

So far, so sunny. It hasn't rained here since before Christmas. Doesn't seem like it's about to start.