Who put footy prints all over my rock?

Doesn't look like much, does it? And, really, it isn't. That is a slab of shale, about 6 cm x 7 cm. And, it's about 1/2 cm thick. So, not very big.

But, it kind of looks like theres something on that rock, doesn't it?

Sort of reminds you of an aerial view of some N-Gauge train tracks, right?

That's not what it is, either.

It is my newest fossil. (yeah, I know....I've been on a buying spree lately...) I showed a picture to my friend and he asked if it was a fossil of a millipede.

Nope. It is not. Although, it does vaguely resemble one.

This is another example of an ichnofossil. For those that don't remember, or missed this post, an ichnofossil is a trace fossil that doesn't preserve the actual organism, but the evidence the organism left behind.

The last ichnofossil I showed was a rusophycus, or resting place of a trilobite. This fossil is called a Cruziana.

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Some trilobites swam suspended above the sea floor, but the majority of them walked along the sea bed. Cruziana are the footprints the trilobite left as it wandered around looking for food.

Some cruziana start or stop in a rusophycus, while others will preserve the evidence that the trilobite found something to eat. Generally in the form of disturbances in the muck where the trilobite attacked and devoured it's prey, and then moved on.

We can tell from this cruziana that the trilobite was walking. That's because the tracks are somewhat deep and merge together. When a trilobite ran, because it needed to escape or to catch food, the tracks would be more defined and further apart. When the tracks show running, they are called Diplichnites.

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Not all cruziana were made by trilobites. Some have been found in non-marine formations, and also in Triassic era deposits. (trilobites died out in the Permian Extinction event, before the Triassic).

Cruziana found in beds that date to trilobite eras, however, are generally considered to be trilobite as it was the prime arthropod of the time. But evidence shows other arthropods would make them.

We really have no sure way of telling what trilobite created these tracks as there are several species associated with the formation where the tracks were found.

These particular tracks come from formations that date to the Pennsylvanian Era, (323 million years ago to 299 million years ago), which is the later sub division of the Carboniferous Era. (the Carboniferous is when all the new vegetation died and was compressed into coal). The Pennsylvanian was the era just before the Permian, and the trilobites died off for good at the end of the Permian.

So, these tracks come from the later years of the trilobites reign.

I must apologize for the quality of the picture. It really doesn't do the tracks justice. They are much sharper and distinct when viewed with the eye, and not through the lens of my smart phones camera.

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I still have a few fossils to highlight, but will do those later. So for now, enjoy my little footy prints.

*Authors Note*

That line at the beginning of the post? The one about footy prints on my rock? That's a variation on one of my favorite lines from a Bugs Bunny cartoon. In the cartoon 'Sahara Hare', Yosemite Sam was riding a camel across the desert when he spots Bugs Bunnys foot prints in the desert. (shoulda taken that left at Albuquerque) Upon seeing the foot prints, he stops and yells, "Who put footy prints all over my desert?". But, I'm odd, so it stands to reason I like odd quotes.