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Specimen of the Week: Week 171

By Mark Carnall, on 19 January 2015

Scary MonkeyThis week’s Specimen of the Week is one of those animals that is easier to talk about in terms of what it isn’t rather than what it is. In a previous blog post I’ve written about the fun with naming and language that happens when common names meet scientific classifications and how we end up with eels which aren’t eels, crabs which aren’t crabs and the brilliantly named flying lemurs which don’t fly and aren’t lemurs.

When it comes to fossil organisms there’s often even more fun to be had as it’s very rare that fossil groups are given common names so we end up having to refer to them by what living animals they aren’t or nearly are. This week’s specimen of the week is one of those organisms, I’ll do my best to try to explain what it is below.

This week’s specimen of the week is…

 ** Xiphosuran fossil Euproops rotundata**

Image of LDUCZ-J23 Euproops rotundata fossil

LDUCZ-J23 Euproops rotundata

1) What’s in a name? Xiphowhonow? you may well be asking. Xiphosurans are a group (the taxonomic level of which is constantly fluctuating, some authorities list it as a class, others an order) of arthropods that are only represented today by four species of horseshoe crab. The name horseshoe crab is a bit of a misnomer as they are very poor for shodding horses with and aren’t crustaceans at all. They are most closely related to spiders, sea spiders, scorpions and the extinct sea scorpions although again the exact positioning and relationships of these groups are uncertain. Further confusing the issue is that fossils in this group resemble another group of arthropods, the trilobites, but this similarity is superficial, the ‘segments’ of Euproops are similar but not the same as in trilobites. The specimen of Euproops rotundata we have here is an extinct non-living possible horseshoe crab (it’s not clear the exact level that the name horseshoe crab applies to either) xiphosuran and that’s as close as we can get to some semblance of a common name so that’s as clear as mud then.

2) Swamp Thing This specimen was collected from the 310 million year old Carboniferous ‘Iron stone bands of the Dudley coal fields’, and specimens of Euproops are well represented from coal measures across Europe and North America. It’s thought that many Euproops species lived in coal swamp lakes and streams and at least one author has proposed that unlike living relatives who only leave the sea temporarily to breed, organisms in this genus may have spent some time fully living out of the water (Fisher 1979) although this theory is still largely contested today.

3) Transform and Roll Out A related species Euproops danae, possessed a unique armament of spines extending from the prosoma (the head) that lead one researcher, the same one from above, to suggest that this species could fold in half when threatened whilst swimming and then steadily fall through the water column without tumbling or rolling (Fisher 1977). It just so happens that when folded up this species resembles any number of science fiction space fighters, perhaps making this species the original transformer, albeit one that would hardly give Optimus Prime and co. a run for their money.

Image of reconstruction of a group of Euproops floating in fighter formation

Reconstruction of a group of transformed Euproops floating through water in ‘fighter formation’. That’s marine snow in the background, definitely not stars of course. Reconstructed by the author after Fisher 1977.

4) A Lankester Specimen? It’s not clear when this specimen came into the Grant Museum. The specimen carries one of our older labels and given that former curator E.Ray Lankester was the first zoologist to show the relationship between horseshoe crabs and arachnid arthropods it would be compelling to assume that this was one of the original specimens from Lankester’s collection and one he may have studied. However, this specimen doesn’t appear in the 1890’s catalogue of the collection that Lankester published, leading us to conclude that this specimen probably wasn’t added to the collection until after Lankester’s tenure here.

5) A Euproops by any other name.The old specimen label for this specimen records this individual as Prestwichia sp. named after Joseph Prestwich a businessman, geologist and UCL alumnus who described a number of xiphosuran species from British coal measures. Unfortunately, this name had already been given to a species of wasp. Prestwichianella was suggested as a replacement name but unfortunately this name was later synonymised to Euproops alsoDespite this error it is still very common to find fossils identified as Prestwichia in museum catalogues and displays. The name Euproops was coined in 1867 but I’ve not been able to track down the etymology of this slightly odd-looking combination. If there are any readers who enjoy hunting down the etymology of scientific names, please do leave a comment if you can succeed where I’ve failed and find out the meaning of Euproops. 


Fisher, D.C. 1977. Functional Significance of Spines in the Pennsylvanian Horseshoe Crab Euproops danae. Palaeobiology. Vol. 3, No. 2. pp.175-195

Fisher, D.C 1979. Evidence for subaerial activity of Euproops danae (Merostomata, Xiphosurida). In Nitecki, M.H.; ed.) Mazon Creek fossils. Academic Press, New York. pp.379-447
Mark Carnall is the Curator of the Grant Museum of Zoology

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