Talk:Eurypterid

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I'm amazed! I add a little to the eurypterid stub from my off-hand knowledge, intending to come back and add to it in a more scientific manner, and here a few hours later it's nearly all been filled in! Great! One quarrel though,

   "They also had a pair of pincers, known as chelicera."

I do believe the pincers constitute pedipalps, not chelicerae (singular chelicera), which are more like mouthparts/fangs. I won't change it, though.

umm, '8 pairs of walking legs' ? i believe it's 4 pairs, 8 total. the thing is i remember entering 8 pairs, as a typographical error, and correcting it later.. so if that's still there, someone must be challenging it?

I am adding to the discussion:

Pedipalps like the ones in scorpions are homologous to the first pair of walking legs in Eurypterus. The chelicerae in scorpions are anterior to the pedipalps and smaller. In the case of scorpions both the chelicerae and the pedipalps have pincers (chelae), but in spiders for example, the pedipalps are non-chelate. In male spiders the pedipalp carries a spermatheca. In horseshoe crabs, and apparently in some eurypterids, the first pair of legs in males has a hook-like modified distal segment specialized for holding onto the female carapace during mating. Horshoe crabs have the same number of prosomal appendages as Eurypterids and scorpions (6), but the walking legs with the exception of the last pair are chelate. One has to specify "prosomal" appendages because these animals have also abdominal appendages (gills). It is tricky to be precise, and at the same time concise and plain-spoken.

Concerning the walking legs in eurypterids, the total number of prosomal appendages is always six, but the number of walking legs is variable, because some appendages are specialized for uses other than walking: swimming, grasping. Thus, Eurypterus and Pterygotus have four pairs of walking legs, one pair of swimming appendages or paddles, plus the chelicera with pincers at the front end. Stylonurus has five pairs of walking legs, plus the chelicera and Mixopterus and Megalograptus have two pairs of grasping appendages, two pairs of walking legs and one pair of swimming appendages plus the chelicera. Thanks for reading.

Manuel O. Diaz

[edit] The most fearsome swimming predators of the Palaeozoic?

"Eurypterids were the most fearsome swimming predators of the Palaeozoic." Well, let's see -- "The largest [eurypterids], such as Pterygotus, reached 2 m or more in length ..." Compare with Placoderm fish such as Dunkleosteus, "around 8 to 10 m (27 to 33 feet) long", "scientists at the Field Museum of Natural History and the University of Chicago concluded that Dunkleosteus had the most powerful bite of any fish, well ahead of sharks, including the Great White. Dunkleosteus could concentrate a pressure of up to 8,000 pounds-force per square inch (55 megapascals) at the tip of its mouth, effectively placing Dunkleosteus in the league of Tyrannosaurus rex and modern crocodiles as having the most powerful known bite." -- 201.51.231.176 20:28, 6 March 2007 (UTC)

Well that might be true for a preserved specimen, in should be staed that of all fossilised species discovered so far.....etc. As you know not all species are preserved and there might have been bigger, meaner, nasties things alive back then. But you are generally correct. I think the statement comes from the show, 'Walking with Sea Monsters. Enlil Ninlil 03:53, 7 March 2007 (UTC)