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.
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.
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.