Despite the title of this blog, I am a genuine enthusiast of pretty much all animals, though like most I am certainly far more partial to hypercharismatic megafauna* (an apparent piece of horrible corporate-speak but actually a genuinely useful term, c/o Desmond Morris) than others. Despite my bias, this is one of my favourite fossils of all time, and sadly the photo really does not do it justice.
As many palaeontologists will tell you, and as I mentioned recently with the new Chinese theropod tracks, working out which animals left which tracks can be a very tricky thing indeed. What you *really* need therefore is something like this to help you out:
This poor little Limulus (that’s a horseshoe crab) was tottering along on the bottom of a nice lagoon leaving a beautiful trial of tracks for future palaeontologists, right up to the point where he snuffed it and he himself was covered. Yep, this is one of only a handful of fossils worldwide where we have both the tack and trackmaker in direct association such that the identity is pretty much unambiguous. This is of course incredibly useful if you want to know what kind of tracks these animals leave, and also just an amazing fossil.
It comes, perhaps not surprisingly, from the German Solnhofen beds that yield Archaeopteryx (the urvogel), numerous pterosaurs (hooray) and plenty of other fossil life including numerous insects, plants, marine reptiles and rarities like squid and jellyfish (yep, they *do* have a fossil record). Even so it’s an exceptional piece about three metres long (it carries on to the right for soem way, the crab is only about 15cm across) and of course it is a wonder that not only was it found, but recognised for what it was (not may people bother to collect invertebrate trackways, well, not huge slabs of them) but that it was recovered unbroken and in superb condition. You can see it at the Jura Museum, base of the great Helmut Tischlinger and a number of other famous fossils including an Archaeopteryx, the dimunitive theropod Juraventaor, and plenty of important pterosaur specimens.
* If you had not worked it out, it basically means ‘big exciting animals’. It was originally intended to be somewhat tongue in cheek I think, but it has gained a certain popularity.
Dave Hone's Archosaur Musings 
Isn’t the Solnhofen xiphosuran Mesolimulus, not Limulus?
That being said, there are several of these “death march” specimens known from the Solnhofen: little guys get washed into dysoxic layers, and die in their tracks. Very useful in intro classes for illustrating the difference between trace fossils and body fossils.
You might be right there Tom, the identification was an assumption on my part (though the specimen itself is unlabelled in the museum). I’ll ask my Solnhofen colleagues and check back on this, thanks for the heads-up.
So, suppose I had spent more time at the beach when I was growing up (I come from northeastern U.S., where Limulus is reasonably common): do the traces look enough like those of modern horseshoe crabs and are they distinctive enough that I could have guessed who left them without the corpse?
(Spectacularly beautiful fossil, b.t.w. Solenhofen has yielded truly wonderful stuff.)
I don’t know but my suspicion is yes. That is, I bet Limulus tracks look a lot like this. What I don;t know is if the tracks of other beasties like crabs and lobsters could be mistaken for them.