Wednesday, November 21, 2007

sea scorpion

THE discovery of a giant claw from an ancient sea scorpion suggests creepy crawlies such as spiders could have been much larger than previously thought.

The prehistoric pincer, found in a quarry in Germany, was 46 centimetres long, which means the creature it came from probably stretched to 2.5 metres.

That is almost half a metre longer than previous estimates for this sea beast, making it the largest arthropod that ever lived.

"This is an amazing discovery," said researcher Dr Simon Braddy, of the University of Bristol's department of earth sciences.

"We have known for some time that the fossil record yields monster millipedes, super-sized scorpions, colossal cockroaches and jumbo dragonflies, but we never realised until now just how big some of these ancient creepy crawlies were."

The 390-million-year-old claw comes from a species of sea scorpion known as Jaekelopterus rhenaniae that lived between 460 and 255 million years ago.

Arthropods, like this ancient monster, are characterised by segmented bodies, jointed limbs and a hard external skeleton, and include insects and crabs.

These sea scorpions are thought to be the aquatic "sisters" of scorpions, and possibly all arachnids, including spiders.

The findings were reported online yesterday in a paper published by the Royal Society's Biology Letters, which outlined theories about why giant arthropods evolved.

Some scientists believe it was due to higher levels of oxygen in the atmosphere, which reached 35% during the Carboniferous period between 359 and 299 million years ago, compared with 21% today.

Others attribute their size to an "arms race" with their prey, such as armoured fish.

Dr Braddy, a co-author on the paper, said there was no simple explanation for the giant beasts. "It is more likely that some ancient arthropods were big because there was little competition from the vertebrates, as we see today," he said.

"If the amount of oxygen in the atmosphere suddenly increased, it doesn't mean all the bugs would get bigger."

Enormous arthropods already revealed in the fossil record include millipedes that were two metres long, and dragonflies with wings that spanned 75 centimetres.

Dr John Long, head of sciences at Museum Victoria, said this sea scorpion lived at a time of low oxygen, but one explanation for its size could be high levels of dissolved oxygen in the water.

"This was the largest sea creature of its day, it was the whale of the Devonian (period)." He also said that during this time, about 355 to 408 million years ago, fish were "evolving and radiating".

"It means there was a lot of interesting dynamics going on in the ecosystem. We have these giant arthropods at the same time as fish were trying to get a grip on evolution," he said.

"It's a very interesting discovery and it also means we have the potential to find other really large arthropods from beds of the same age."

Things were tough back in the Paleozoic Era. Violent storms, huge changes in oxygen levels, not much dry land. And in the water there were giant, carnivorous sea scorpions.

Scientists already knew these creatures were big. Now they've found a fossil from the biggest sea scorpion yet.

Four hundred million years ago was a bad time to go swimming. There were lots of predators. And Erik Tetlie, a paleontologist at Yale, thinks sea scorpions were the scariest.

"They kind of looked like a flattened submarine," Tetlie said. "Then they had these massive claws in front which could be up to a meter long. And then they have five pairs of legs, and the last of these were the swimming legs, which were flattened paddles."

Kind of like a lobster big enough to play in the NBA.

Scientists call the sea scorpions eurypterids. Tetlie said even the fossils are intimidating.

"My supervisor in Bristol used to say that he would rather be in a pool with a shark than in a pool with a eurypterid and I think I would agree with that," he said.

Tetlie, and his former boss, are part of an international team reporting on a new fossil that is likely to enhance the sea scorpion's frightening reputation. The fossil came from a quarry in Germany. It is part of a claw, and it is about 18 inches long. The creature it came from was probably eight feet long — a record.

Tetlie said giant sea scorpions apparently led a simple life.

"They probably ate primitive fish, other smaller sea scorpions, whatever they can get their claws into," he said.

But unlike modern scorpions, they did not kill their prey with a poison stinger.

"They would probably just sort of sink their fangs into it and start munching away," he said.

Lorenzo Prendini is a scorpion expert at the American Museum of Natural History in New York. He said eurypterids did not need a stinger to subdue their prey.

"The spines on the claws would have inflicted a lot of damage," Prendini said. "They may have even ripped them apart with the claws. But I think a combination of that and the actual jaws, which are quite well developed with fang-like structures would have done the damage."

Sea scorpions had their tender moments, too. Like when thousands would gather in the shallow water to shed their outer skeletons and mate.

About 255 million years ago, the sea scorpions disappeared.

One factor may have been a decrease in the amount of oxygen in the oceans, but Prendini thinks they just got eaten — when something even bigger and meaner evolved.

"There were certainly some enormous dinosaur relatives of the day — ichthyosaurs and the like. I think they would have made short work of these guys," he said.

And survivors may have become smaller and ended up on land — though the fossil record isn't entirely clear on that.

"Modern scorpions are more closely related to other arachnids like spiders and mites and a host of other peculiar creatures than they are to the sea scorpions, but all of them shared a common ancestor at some point in time," Prendini said.

As for the giant sea scorpion, it is still a big deal in places like New York — where it is the official state fossil.

The new finding is described in the current issue
European researches have discovered an immense size of a sea scorpion in Germany, the immense fossilised claw of a 2.5m-long (8ft).

The fossil record has yielded various gigantic arthropods, in contrast to their diminutive proportions today.

The recent discovery of a 46cm long claw (chelicera) of the pterygotid eurypterid ('sea scorpion') Jaekelopterus rhenaniae, from the Early Devonian Willwerath Lagerstätte of Germany, reveals that this form attained a body length of approximately 2.5m—almost half a metre longer than previous estimates of the group, and the largest arthropod ever to have evolved.

Gigantism in Late Palaeozoic arthropods is generally attributed to elevated atmospheric oxygen levels, but while this may be applicable to Carboniferous terrestrial taxa, gigantism among aquatic taxa is much more widespread and may be attributed to other extrinsic factors, including environmental resources, predation and competition.

A phylogenetic analysis of the pterygotid clade reveals that Jaekelopterus is sister-taxon to the genus Acutiramus, and is among the most derived members of the pterygotids, in contrast to earlier suggestions. - Source: Journal of
LONDON - This bug was so big it may have taken a whole can of Raid to take it out. Picture a scorpion that's eight feet long.

British scientists have recently stumbled on a massive fossilized sea scorpion claw, which has them thinking that spiders, insects, crabs and other such creatures were much bigger in the past than previously realized. One of the researchers says they knew ancient bugs were big, but the size of the scorpion is an "amazing discovery."

The study, published online in the journal Biology Letters, finds that before it became extinct, this ancient sea scorpion -- which existed in Germany about 400 million years ago -- was much longer than an average man's height. The researchers say the scorpions were cannibals, so their survival depended on their size.


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