Tag Archives: Trilobite

A pretty darn good bad cast

There. I have said it. This may be the only time I say it, so I will say it again. This is actually a pretty darn good bad cast. Two casts actually.

Can I say it? Go on. A rather beautiful cast of the top and bottom of a trilobite.

Can I say it? Go on… A rather beautiful cast of the top and underneath of a trilobite.

Apart from a few scuffs where the paint has rubbed off, and a little pink crayon where someone has used this for some children activity as a fossil rubbing, they are actually quite beautiful. (Please don’t use accessioned museum specimens for crayon rubbings. You can buy cheapish casts from fossil suppliers, then place a piece of paper over it and rub a crayon on top. It comes out with a lovely rubbing of the fossil.)

The previous bad casts have been awful. Shocking. So terrible that I have had to really look into what they are supposed to represent. But these are good. Really good in comparison!

What has me even more excited is that there is information written on the back! Can you imagine! A bad cast with information!

Striking gold! Information about a specimen with a specimen! A true rarity in itself!

Striking gold! Information about a specimen with a specimen! A true rarity in itself!

The information tells us what the fossil was, where it was found and who made it. It is a cast of a trilobite, which were pretty successful marine creatures living from around 520 million years ago until the whole group became extinct around 250 million years ago. From species smaller than a finer nail to the big Welsh beasts that would have terrified us paddling in the shallows, trilobites were amazing creatures. Some could roll up into balls for protection, like a woodlouse might today. Others had exquisite spines and spikes growing out of their hard external skeletons.

This cast is of the beautiful trilobite Triarthrus eatoni which lived around 440 million years ago (the Upper Ordovician Period). These casts are actually casts of models of this trilobite. But why the models themselves were made is wonderful is all part of their story.

The Ordovician sediments at a small site in Rome, New York, preserved trilobites and other creatures in unbelievable detail. They were discovered in 1892, and came to the attention of Mr Charles Beecher who was working at Yale University. Beecher noticed that almost everything of this trilobite was preserved, the antennae, and even the gills on the legs.

Gorgeous, almost perfect, pyrite fossils of the little trilobite.

Gorgeous, almost perfect, pyrite fossils of the little trilobite. Image from here.

The specimens themselves were about as long as my thumb. To truly show them off, Beecher made larger brass models with this new understanding of trilobite anatomy. The models are not exactly the same as the fossils, but Beecher appears to have been given a little artistic licence.

These casts are of Beechers models. They show a lot of detail of these extinct creatures. Long antennae coming out from under the head can be seen. These would have been used to sense movement and chemicals in the water. Feathery gills attached to each leg let us see how trilobites were able to breathe under the water. Such soft tissue preservation is very rare in the fossil record, because it decays so quickly.

This will be the only time we get excited about a rather good bad cast. There are a few shockers to come. Lets enjoy this one.

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Size is important for these bad casts

A nice circular cast of  a lovely trilobite. Its a bit trilobite, one of the biggest, and if you look close enough you might be able to make out its body. Just.

A nice circular cast of a lovely trilobite. Its a bit trilobite, one of the biggest, and if you look close enough you might be able to make out its body. Just.

For one of the biggest species of trilobites ever to have lived, you would expect a spectacular cast. I don’t want to disappoint; it wouldn’t be a bad cast if it was spectacular, would it?

This oversized trilobite* was first found in the early 1860s at St David’s in Pembrokeshire. The smallest city in the UK held one of the largest trilobites ever to have swam in the seas. It’s species name provided immortality to the place it was discovered; Paradoxides davidis. (Click here for some very nice images of real big fossils.)

This is a big specimen. Almost half a metre in length, as long as my fore-arm. It is badly painted (as we would expect by now) and very chipped. Being so chipped may indicate lots of use for displays and talks about this fossil; it is more likely that people didn’t really think it was important, so didn’t handle it well. You can just about make out the axial ring (what looks like the spine running down the middle of the trilobite) and possibly a few ‘rib’ like things coming off the axial ring. Nothing else is very clear.

You can see it is a trilobite, but I doubt you would use this specimen to examine the anatomy of these extinct creatures.

Luckily for us, there is a second cast of this beast. (Obviously, we use ‘luckily’ rather loosely.)

A trimmed Paradoxides davidis. The 'trilobite' is shinier than the 'rock'.

A trimmed Paradoxides davidis. The ‘trilobite’ is shinier than the ‘rock’.

It is another stonker of a specimen at almost half a metre long! This second cast of P. davidis looks intriguingly as though it has had its back and sides trimmed. The hairdresser went by the name of Plate Tectonics. The particular rocks this trilobite was preserved in had been heated and crushed causing fractures cutting through the rock in a thousand different directions when it eventually cooled. When the original fossil of this cast was excavated, it is likely that there were fractures running through the fossil. I have found similar fossils which have crumbled away in my hand. A fossil can be lost in a hundred fragments; after surviving for millions of years it is lost forever in an instant. Sometimes though, we may be more lucky and some of the fossil does survive the fractures.

The world these giants were living in was very different from today. They were swimming in ancient seas around 510 million years ago, during the Cambrian Period. 510 million years! Amazing! These remains have survived scavengers, being crushed by tonnes of rocks on top of them, being heated and deformed, being thrust up onto land, and exposed to the elements! And we can see them!

510 million years ago, life had really just begun. Well, complex life had; single celled organisms had been around for at least 3 billion years before. In the Cambrian Period, there was no life on land; it was a barren, desolate place. The seas, however, were teeming with life; trilobites swam below the water’s surface, while others buried themselves in the sediment. Our big friend was very likely to have been a hunter. Although you cant see from these casts, they had big eyes, most likely used for hunting. They would most probably hunted small invertebrates (animals without a backbone) in the seas.

These were some of the largest trilobites to have lived. There were bigger ones, such as the enormous Isotelus rex which was longer than a cat (up to 70cm long). These extinct creatures open up a world long vanished. Long vanished, but not forgotten.  

This giant is worthy of two casts. They may not be very clear, and were most likely painted by unskilled painters, but they are big. And it seems that the size of these casts compensates for other less satisfying features.

*A bit of background to trilobites can be found on the first bad cast post: The ghost in the rock.

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The ghost in the rock

 

One bad cast. The blurry shape is in fact a real cast of a fossil.

One bad cast. The blurry shape is in fact a real cast of a fossil.

There is nothing wrong with your computer screen. Do not attempt to adjust your monitor. I won’t make the volume louder or quieter, because I have no idea how to do that. I want to change the focus to sharpen it to crystal clarity, but this image is in focus, it is the cast that is crap. For the next three minutes, sit comfortably and try to read on (if you want to). You are about to participate in a great adventure. You are about to experience the awe and mystery which reaches from the inner mind to – the really bad world of fossil plaster casts.

And what an adventure. This is the first in a series of bad casts. And it is shockingly bad. The image is in focus, so it shows in all its beautifully terrible glory, just how bad the cast is. The makers didn’t even paint it to spruce it up a little.

(Before I begin, I should say, that none of the casts featured in this series were made in schools, or nurseries, or playgroups, or kindergartens. They were all done by professionals. This is important to remember as other casts are revealed.)

This cast could be a blurry centipede. It has segments and what appears to be long legs. The detail is very poor. Luckily, the old trusty old accession card reads Acidaspis buchii. A quick Google – it’s a trilobite.

Trilobites were a big group of arthropods (jointed animals) that lived from the Cambrian Period (around 520 million years ago) until the Permian Period (around 270 million years ago). Although incredibly successful animals, they only lived in the marine environment. To date there have been not fossils found in rocks from land environments.

Trilobites get their names from their body shape – ‘three-lobed’. They have a head (cephalon), a body (thorax) and a tail (pygidium). With a hard segmented exoskeleton, some could roll up into balls, whilst other grew elaborate spines, for defence.

Although you wouldn’t think so from this example, they are really quite cool creatures. Fossil remains of these extinct creatures show they were incredibly abundant during their 250 million year reign. These creatures evolved into hundreds of different species from as small as a 5 penny piece to bigger than a cat. Some were efficient swimmers, others browed deep in the mud. Some had eyes; deep sea ones didn’t.

This ghost of a trilobite, Acidaspis buchii, is from the Ordovician Period (around 450 million years ago). It was quite a big trilobite filling my outstreched hand. What looked like long legs are likely to be spines growing out from the segments in the thorax. You may be able to make out two very faint, faded circles on the head. These are eyes.

From this, I would say when this trilobite was alive, it was scurrying on the sea floor; spines on the side, and possibly top, were there to protect it from predators. It’s eyes suggest a shallow environment, where light could reach the sea floor letting the trilobite see.

Is this a good cast? Not particularly. Would you take it home to show the old folks? Not on your nelly. You can barely make out any features of the animal. Without the old accession card, I could have believed it to be a centipede.

It is a very bad cast. But there are worse to come. Much worse.

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