Tag Archives: fossil

The croc in the rock

Number 16 of this series of bad casts is another shocker. All the casts are actually really bad (possibly apart from that pretty darn good bad cast, but this is a cast of a model, not a real fossil). It is amazing how truly bad these casts are and nobody seems to have ever questioned them!

This week’s specimen fails to excite, as you would expect by now.

Another terrible bad cast. A head of a crocodile and a few vertebra. Remember, these bad casts actually belong in a museum. Why?!

Another terrible bad cast. Remember, these casts actually are in a museum collection.

 

The ‘rock’ for this cast is fairly good for a change. Normally, the ‘rock’ (the block the fossil sits on) is just splattered with one colour where you can see the enormously clumsy brush strokes. This one has a little shading, and even a couple of ‘cracks’ thrown in. Nice touch.

The ‘rock’ looks pretty real. This (momentarily) takes your eyes away from what you are supposed to be looking at; the tennis racket in the middle of the slab.

The tennis racket is, of course, the cast of the fossil crocodile head. There are a few other bones included; two vertebrae and a leg bone. Presumably these were on the original fossil.

‘Presumably’, ‘probably’, ‘may have’, are words that often come up in this series of posts, because there is very little information with the specimens. With this cast there is a faded number but no information.

We can make educated guesses about what it is and why the museum possibly has it.

Looking at the snout, I know it is a crocodile skull. Alligators have wider snouts, whereas crocodiles have long thin snouts. It is quite a small specimen, but why have one?

I have a tingly feeling that all of these bad casts may have once been used to illustrate life through time. The collection of casts includes some trilobites, some ancient fish and even a dinosaur tooth. There are some mammals as well (which will come in the next few weeks). This crocodile ‘fossil’ may well have been used to show the people of Plymouth in 1910 a selection of different creatures that lived millions of years ago. Although the fossil is pretty bad, the choice of animal pretty good.

True crocodiles evolved around 200 million years ago. Before these, the ancestors lived on land and looked a little different. In the skull you can see four holes;

Another terrible bad cast. A head of a crocodile and a few vertebra. Remember, these bad casts actually belong in a museum. Why?!

The crocodile skull has four holes on it’s head.

The front two holes are for the eye sockets. The two holes at the back are shared with many other animals, including, birds, snakes, lizards, dinosaurs, rhynchosaurs and others. These two holes (found in diapsids) would have attached muscles to the head. Because they are present in all these animals (including some other extinct ones), it shows that they are all closely related. But crocodiles and birds are even more closely related.

Crocodiles, dinosaurs and birds all belong to the group called archosaurs. This group is defined by the animals within it having two extra openings in the front of the skull (below the eye sockets). Sharing a similar feature like this means that the animals in this group all shared a common ancestor which split apart and evolved into some incredible forms!

Around 250 million years ago, during the Triassic Period, the dinosaurs were becoming the dominant land animals. The ancestors of crocodiles (known as crocodylomorphs) had evolved to take advantage of a number of food sources, including insects, meat, plants and fish. These land loving ancestors felt the pressure of the successful dinosaurs, and around 50 million years later, during the Jurassic Period, crocodiles were living solely in the water.

It was at this time, around 200 million years ago, that crocodiles began to look like crocodiles. Before then they were strange reptiles, some with nostrils on the tops of their heads (rather than at the end of their snouts), and others walks on two legs. They waited patiently in the rivers while large dinosaurs were taking sips of water, and some grew to enormous sizes to tackle this larger prey. The enormous Sarcosuchus was almost as long as a basketball court (around 20m), and would have enjoyed a dinosaur for dinner.

There is more information behind a bad cast than would first appear. A lot of information can be told around this bad cast and we can work out why the museum purchased it.

I may be trying to make this bad cast look extremely good with all the exciting information. Our educated guesses may actually be nothing more than an old Christmas present to a previous curator who left it in the office by mistake. I will never know.

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The king lizard whale

This weeks bad cast doesn’t really look like a fossil, yet it may be from a creature you might recognise.

 

A very very poor quality cast. Those pesky fossil cast dealers.

A very very poor quality cast. Those pesky fossil cast dealers. Doesn’t look like much, does it?

 

I nearly took the photo this way by mistake;

 

Has someone made a cast of a banana?

Has someone made a cast of a banana?

 

Even worse, I almost took the photo this way;

 

Well. Good job I didnt take the photo this way.

Well. Good job I didnt take the photo this way. Otherwise, this could have been mistaken for a cast of something unimaginable. 

Shocking. Not the shape of the fossil (which is a little), but the quality. How can this be sold as a cast of a ‘real’ fossil? It has. Frustratingly it was 108 years ago, so the dealers cannot be challenged by trading standards. There is no time travelling ombudsman. (Now there’s a cool job.)

This is actually a cast of a fossil tooth! The tooth does exist somewhere, but you wouldn’t be surprised to know that there is no information with this specimen about the original fossil. That would be giving us too much!

The label names the tooth as belonging to Zeuglodon cetoides. This extinct beast is actually one you may recognise; Basilosaurus cetoides. It’s an amazing creature, with an interesting history.

In the earl-1800s, huge fossil bones had been discovered in the sediment of the American South. Huge, and fairly common, these had been used as furniture! A couple of bones were sent to the American Philosophical Society for identification. (The American Philosophical Society was set up in 1743 by Benjamin Franklin and John Bartram and early members included three presidents of the United States of America).

The anatomist who looked at the bones (mainly the bones from the spine; the vertebra), Richard Harlan, compared them to the (then) recently discovered dinosaur bones of Megalosaurus and Iguanodon. Harlan thought they looked very similar, but bigger. So he named the creature ‘Basilosaurus‘ meaning ‘king lizard’.

Was this another type of giant extinct lizard? Another new dinosaur discovered? Nope.

Harlan visited England and took some of his newly described Basilosaurus specimens with him to show to the great Richard Owen. (Richard Owen was an incredible British  comparative anatomist who was able to identify an extinct animal by one bone. He was brilliant, but he was also very arrogant, egotistical and deceitful.) Owen looked at the fossils and there were traits that looked like a mammal, and lots of similarities to whales. He renamed the giant ‘Zeuglodon‘ and the American anatomist agreed.

However, there are rules when we name animals and plants (and bacteria). Them rules are there for a reason. The rules of taxonomy are there to make sure that an organism doesn’t have five different scientific names. It also gives priority to the first name given. So in the case of this big whale, it was scientifically described as Basilosaurus before it was called Zeuglodon, so Basilosaurus takes precedent.

This tooth belonged to this whale that lived during the Eocene (around 40 million years ago). About as long as 4 double decker buses, it was a heft animal! As you can’t really see, the teeth were quite chunky and pointy; the shape, and that one fossil had a stomach full of fish indicate that they fed on fish in the oceans. Closely related to modern whales, the Basilosaurus were not their ancestors; this group and the group of modern whales shared a common ancestor that lived around 50 million years ago.

A delightful little sketch of two Basilosaurus. Big, long, whales. Lovely. (Image from here)

A delightful little sketch of two Basilosaurus. Big, long, whales. Lovely. (Image from here)

Beneath this shockingly bad cast is the tale of an whale that once swam in the oceans millions of years ago. Fossils, and potentially casts of fossils, reveal such awesome clues to forgotten worlds. Many of the bad casts in this series do not give the original fossil any thing to get excited about. This bad cast is no exception.

 

 

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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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