Monthly Archives: March 2015

The flamboyant cast

Another Bad Cast for your pleasure. Here we have a pretty small cast of a trilobite. You can just make out the outline of this specimen.

Just. But it is a trilobite.

There is a cast of a trilobite on this image. There really is.

There is a cast of a trilobite on this image. There really is.

Unfortunately, as is a recurring theme with these bad casts, this specimen does not convey the true flamboyance of this type of trilobite. It is a cast from the extravagant trilobite family Thysanopeltid. Species in this family of these extinct arthropods are noted for their big gabella (which is the bulging bit in the centre of the head). They also have very elaborate pygidiums (the ‘tail’ segment): almost as long as the main body in some species.

A beautifully preserved (Image from here)

A beautifully preserved Scabriscutellum sp. from Morocco. Note the very elongated tail section (towards the left of the image). (Image from here)

As with all trilobites, they lived in the marine environment. With their large eyes, and relatively flat, streamlined bodies, these unusual trilobites likely lived in the shallow coastal areas where there was light. Staying close to the sandy or muddy floor, they would have scurried along feeding on the tiny organisms in the water as they went.

These were creatures of the Devonian. From around 410 to 358 million years ago, several species from this family were swimming in the warm seas. From Morrocco, North America, and South England, this was a successful family.

The land was slowly being colonised by plants in the Devonian, with some primitive insects scuttling through these alien forests. The seas were different: they were rich, full of diverse life.  With giant armoured fish longer than me, coral reefs, and hundreds of different types of trilobites, this was a world owned by the marine creatures. Stepping barefoot into shallow Devononian waters, you would feel the tickle of trilobites running furiously over your feet, while others swimming would accidently bump into your legs. It was a wonderful world.

Towards the end of the Devonian the fossil record shows that there was a huge extinction event, with numerous families of trilobites, ammonites, corals, and some land animals vanishing forever. Around 22% of families had gone, and 75% of species. The causes may have been due to a meteorite impact, or the changing atmosphere due to the spread of the land plants. It was, and still is, a very fragile planet where slight changes have extremely dramatic effects.

Around half of the bad casts at the museum are trilobites. I get why. Plymouth is on very hard, tough limestone. What fossils have survived 400 million years of crushing, burial, heat and uplift, are fragments of corals or sea shells. When the museum opened, like all museums, they wanted to represent life past and present. Without real fossils to purchase, casts were the next best thing. Apparently.

Did they have to be so bad? We will never know why someone, 100 years ago, spent many shillings on so many bad casts. What is worse for this particular cast, is that species from this wonderful family, Thysanopeltid, have been found in Newton Abbot. Rocks, which are only 40 minutes away. 40 minutes away. Instead of looking for the real thing, we have ended up with this bad cast.

 

 

 

 

 

 

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The beauty of the beast

I will admit it. I am fond of this weeks bad cast. The cast is not unique or unusual. Nor is it particularly striking. The beauty of this beast is unseen.

A familiar cast? It is of course, the wonderful Archaeopteryx.

A familiar cast? It is of course, the wonderful Archaeopteryx.

You will immediately recognise this cast: Archaeopteryx. A cast of one of the most famous fossils in history. Preserved almost perfectly for around 150 million years, this is a truly beautiful creature. The preservation on the real fossil is so incredible even the feathers have been fossilised. This is down to the exquisite limestone they have been encapsulated for an immense period of time: the Solnhofen Limestone.

The limestone in Solnhofen, Germany, has been quarried for centuries. Forming around 150 million years ago this was once at the edge of the now extinct Tethys Sea. Here, there was a beautiful, sparkling lagoon. Beautiful but deadly. With the salinity so high, no organisms could live here. This was good news for future palaeontologists, because no organisms in the lagoon means there is nothing to eat anything that falls into it. Added to this was the incredibly fine carbonate mud falling to the bottom. So not only was anything that fell into the lagoon protected from scavengers, their bodies were covered in extremely fine sediment. The result – exquisitely gorgeous fossils including plants, insects, pterosaurs, and of course Archaeopteryx.

Admittedly it is not the most detailed cast ever produced. Made with a rather thick, powdery Plaster of Paris, you can only just make out the outline of the wings. Today, fine resins make much more detailed casts of fossils, often reproducing the smallest of details.

This cast is certainly not rare. Almost every museum in the UK will have a copy of this famous specimen. So confident that you are guaranteed to see this cast, my chum at UCL’s Grant Museum of Zoology, Mark Carnall, included it in his slightly tongue-in-cheek, ‘Museum Bingo’. Here you take the Museum Bingo card into a museum and cross off the specimens you see. More often than not, you will shout ‘Bingo’!

And it is true. There are plenty of them about. I have seen an Archaeopteryx proudly displayed in a case right next to the front doors welcoming all visitors. In another museum, a quirky ‘real life’ model of an Archaeopteryx is perched valiantly next to the cast. One museum goes one step further and boldly places the cast on the wall to explain bird evolution: it is the only specimen on the wall and I am really sure it works.

So why, if nearly every museum in the UK has a copy, do I have such a secret crush on this bad cast?

True beauty is not in what something looks like. Something that appears beautiful can actually be quite the opposite. I have known a couple of people whom many would say are beautiful. They have strong features, soft skin, big eyes. But to me, they were not beautiful. They lacked personality, humour, empathy, kindness, or warmth. These are the features that make someone (or something) beautiful. The ability to make someone smile; to have interesting, engaging chats; to understand others and to have that warmth of kindness in their eyes. There are so many truly beautiful people in the world. And it is their beauty that really shines.

This Archaeopteryx cast is beautiful. There are only 12 specimens of Archaeopteryx in museums in the world. Twelve. Being so rare, not every museum can hold a specimen. But that doesn’t stop every museum from wanting one. Because these were amazing animals.

Archaeopteryx is one of those ancient animals that have caused heated debate ever since it was first discovered. It is incredible because it has gorgeously preserved feathers; real, long, asymmetrical feathers, which are used in birds today for flight. But there are traits in this creature that cannot be seen in birds today:

  • Archaeopteryx had fingers: birds today have three fingers (digits ii, iii, and iv) which have shrunk or fused to form an extra one in the wing.
  • Archaeopteryx clearly has teeth: birds today lack teeth in their beaks. Some chicks have an ‘egg tooth’ to help them get out of the egg when they hatch.
  • Archaeopteryx had several bones in its tail: birds today have a small number of 5 or 6 tail bones fused together (called the pygostyle).

A strange creature indeed. And it clearly shows a very close relationship between dinosaurs and birds. Although maybe not a direct ancestor for modern birds, this was a very early type of bird which had wings for flying.

And even after 150 years after it was first discovered, we are still learning new things about this ancient bird. In 20122 a team used the incredibly powerful Scanning Electron Microscope (SEM) to look a feather of Archaeopteryx. Zooming in at such a high magnification brings out features that have not been seen before, including structures of melanosomes: the cells which store the colour of the feather. The team compared the structures to many other bird melanosomes, and it showed this feather was very likely black. Another study looking at more feathers indicated that some were dark and light. Each new fascinating bit of research adds a little extra detail to this enigmatic bird.

Using the bad cast. I like to use Archaeopteryx at events. This week I have been running an event for Science Week. School shave been learning about bird anatomy, plus a little bit of evolutionary history.

Using the bad cast. I like to use Archaeopteryx at events. This week I have been running an event for Science Week. Schools have been learning about bird anatomy, plus a little bit of evolutionary history.

All of these great features, and the historical tales of great debates of Archaeopteryx, make this a wonderful fossil to have a cast of. Does it matter that it is a cast? Not really, no. It was cast from the original fossil. And the cast can be used in many different ways. Many museums have it on display. I don’t. I actually use it for talking to schools or families about anatomy, evolution, adaptation, fossils, history of science…This is one of my regulars I get out for events. And it never fails to impress.

The beauty of this Archaeopteryx cast is it’s ability to inspire. Talking to people of all ages and letting them get up close to this fossil, give a real sense of awesomeness. It may not be the most perfect cast, but goodness me, it really is the most beautiful.

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Hidden beauty

They are back. After a little break, mainly to digest their pure awfulness, bad casts are back. This plaster cast of a real fossil is as bad as you would expect. (And I must remind you, that all the casts in this series are real casts.)

I’m not really sure what this bad cast looks like. But I do know that is looks nothing like the fossil it was cast from. This is another trilobite. Paying homage to the ghost in the rock, this rather blurry replica, gives little detail for the viewer to drool over. Which is a shame, because it is actually from a really cool group of trilobites.

 

A squashed bug you say? Nope. That's a cast of a trilobite.

A squashed bug you say? Nope. That’s a cast of a trilobite.

 

This rectangular slab of plaster does have an museum number with it, and an accession card! That is pretty exciting, because the accession card is a record of all the associated information with that specimen. (Today we have computer databases, but 100 years ago, there were wonderful accession cards.) Very exciting. Well, it would be, if the accession card had any information on it!

Written on the card is ‘Plaster cast white slab’. Yep. Got that.

Then it gives the measurements ‘5 ¼ x 4 ¾’. Pretty pointless.

Finally, the card tells us that this specimen was given by the crooksters Gregory and Gregory. (See previous posts. Several of these bad casts have been sold by those two.)

Accession cards should have information about where the specimen came from, who collected it, when it was collected and any other information. That is standard for museum objects. Without that information, the object may be pretty fro display or education, but scientifically useless.

My trilobite identification skills are not amazing. So I sent an image of this (and several other bad casts) to colleagues at the Natural History Museum, London. They were awesome and identified them as best they could, despite the fact that they were so bad. This trilobite was placed in the Family Cheiruridae. This was a fairly large family with around 83 different Genera, and numerous different species. These are a pretty cool Family of trilobites. With elaborate head spines, and extra large spines growing from the bottom, they are a distinctive group.

Trilobites are sadly now extinct, but they were a very successful group of invertebrates. The first fossils of them can be found at the very beginning of the Cambrian Period (around 520 million years ago), and they evolved to live in a huge number of marine environments. A hard, but thanks to the segments on the thorax, flexible outer shell protected the creature from most predators. Some groups grew elaborate spines from their backs, adding a little extra protection. Others we happy to be incredible simple looking. What a great group of animals. Hidden under the tough outer shell were two dozen or so little legs, each with gills on, furiously kicking giving the illusion of an animal elegantly gliding through the water.

The Family Cheiruridae first appear around 485 million years ago, and vanished around 360 million years ago. That is a long time for a Family to be on the planet. (The Family to which humans are in, along with the great apes, the Hominidae, have only been around for around 14 million years.) And they were are pretty stunning Family too.

A beautiful fossil of Paraceraurus exsul, from Russia. This little beast would have been swimming int eh waters (Image from here)

A beautiful fossil of Paraceraurus exsul, from Russia. This little beast would have been swimming in the waters around 460 million years ago.(Image from here)

Unfortunately we only got the Family for this trilobite cast. Such a terrible reproduction means a positive identification is very tricky. But I do know more than I did about this cast than I did before. These were beautiful animals. Scanning images online of the fossils (here), the detail in the preservation is incredible. Over 400 million years old, and they are exquisite.

It is such a shame that this cast is just so bad. It tells a tale of the beauty and diversity of trilobites. But to look at it, one would never know.

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