Everything about The Eurypterid totally explained
The
eurypterids (sea scorpions) include the largest known
arthropod that ever lived (with the possible exception of
Arthropleuridae). They are members of the extinct class
Eurypterida (
Arachnomorpha,
Chelicerata) and predate the earliest fishes. The largest, such as
Jaekelopterus, reached 2
m or more in length, but most species were less than 20
cm. They were formidable predators that thrived in warm shallow water in the
Cambrian to
Permian from 510 to 248 million years ago. Although called "sea scorpions", only the earliest ones were marine (most lived in brackish or freshwater), and they were true
scorpions. The move from the sea to fresh water probably occurred by the
Pennsylvanian period.
Eurypterus is perhaps the most well-known genus of eurypterid, of which 18 fossil species are known. The genus
Eurypterus was created in 1825 by
James Ellsworth DeKay, a zoologist. He recognized the arthropod nature of the first ever described eurypterid specimen found by Dr. S. L. Mitchell. In 1984,
Eurypterus remipes was named the
State Fossil of New York.
Body structure
The typical eurypterid had a large, flat, semicircular carapace, followed by a jointed section, and finally a tapering, flexible tail, most ending with a long spine at the end (
Pterygotus, though, had a large flat tail, possibly with a smaller spine). Behind the head of the eurypterids were twelve body segments. These segments are formed by a dorsal plate called
tergite, and a ventral plate called
sternite. The tail, known as the
telson, is spiked in most eurypterids like in modern
scorpions and in some species it may have been used to inject venom, but so far there's no certain evidence any eurypterids were venomous. Most eurypterids have paddles toward the end of the carapace and beyond, which were used to propel themselves through water. Some argue that the paddles were also used for digging. It is possible that it was used for both. Underneath, in addition to the pair of swimming appendages the creature had 4 pairs of
jointed legs for walking, and two large claws at the front,
chelicerae. The walking legs had odd hairs, similar to modern day crabs. Other features, common to ancient and modern arthropods of this type, include one pair of
compound eyes and a pair of smaller eyes called
ocelli, in between the other larger 2 eyes.
Many eurypterids had legs big and long to do more than allow them to crawl over the sea bottom, a number of forms had large stout legs, and were clearly capable of terrestrial locomotion (like land crabs today). While functional studies suggest that eurypterids used amazing walking techniques, their
trackways indicate that they used in-phase, hexapodous (six-legged) and octopodous (eight-legged) gaits. Some species may have been amphibious, emerging onto land for at least part of their life cycle. They may have been capable of breathing both in water and in air.
The largest well-described genus of sea-scorpion was
Pterygotus, an arthropod the size of a crocodile. Fossils of
Pterygotus are relatively common although complete fossils are rare. At 2.1 meters long, they were until recently the largest known arthropod ever to have lived. Their fossils have been found worldwide, except in Antarctica.
Arthropleura came close in size, growing to slightly over 2 meters long.
In 2007 a 46 cm claw belonging to
Jaekelopterus rhenaniae (a species originally described in 1914) was discovered, indicating that
J. rhenaniae was 2.5 meters in length.
They had traditionally been considered close relatives to the common
Horseshoe Crab, but most recent evidence places them closer to the
arachnids.
Eurypterid fossils
Eurypterid fossils have a near global distribution. Among the largest eurypterids are the
Hibbertopterina, named after the British palaeontolgist S. Hibbert, who described
Hibbertopterus scouleri at a limestone quarry in
East Kirkton, Scotland, in 1836. Fossil tracks (a form of
trace fossil) were identified recently in
East Lothian, Scotland, as made by a 1.6 meter long
Hibbertopterus (Whyte, 2005).
Eurypterids are related to the modern marine
horseshoe crabs. About two dozen families of eurypterids are known. They went extinct during the
Permian-Triassic extinction event . A predatory
arthropod whose traces are known as
Protichnites, found in Cambrian strata dating from, is a possible
stem group eurypterid, and is among the first evidence of animals on land.
In 2007, a group paleontologists led by Simon Braddy at the
University of Bristol discovered a sea scorpion larger than a human being, which was claimed to have been the largest arthropod which ever lived. This discovery was made in a 390 million year old rock containing the fossil of a huge claw or chelicera.
Further Information
Get more info on 'Eurypterid'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://eurypterid.totallyexplained.com">Eurypterid Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
