Animal of the Week -- November 26, 2007

So sorry about my absence last week,

I shouldn't let work get in the way of what's really important now, should I? So here it is to make up for my absence, a monster animal of the week, for this week's animal is Jaekelopterus rhenaniae.

You will no doubt have heard about the 45 cm claw of a sea scorpion discovered in Germany recently, its owner, at 2.5 m long and armoured with a broad carapace and jointed exoskelton would have dwarfed a human, had it ever met one. Fortunately for us, they've been extinct for more than 400 million years. Indeed, the whole group of sea scorpions are not something you need worry about bumping into on a day out in Bournemouth -- as you might a string jellyfish (Animal of the Week, November 12) or a bunch of chavs -- because they are all extinct, and although most of them did have a long spike at the end of their tails, this probably didn't have a sting in it. Sea scorpions, eurypterids, were possibly ancestors to all scorpions, spiders, and mites alive today.

Along with the 2.5 m millipede Arthropleura, Jaekelopterus rhenaniae is the largest arthropod (the group comprising crabs, insects, tardigrades, and spiders) ever to have lived. By comparison, the largest living arthropod is the Japanese king crab, which can have a leg-span of 3.5 m, but its body reaches only about 40 cm across and it weighs about 20 kg, its two largest relatives would have weighed a darn site more, even before they were fossilised, although the king crab is probably tastier, especially since they were fossilised. Insects and their ilk absorb oxygen through largely passive methods, Arthropleura and Jaekelopterus lived in times when the atmosphere and seas were far richer in oxygen than today, thus allowing the lazy blighters to grow to greater sizes than any modern creepy crawlies.

Anyway, there you go, the sea scorpion, extinct, huge.