Kingdom Animalia
Phylum Arthropoda
Subphylum Chelicerata
Class Merostomata
Order Eurypterida
Suborder Eurypterina
Family Megalograptidae
Genus Megalograptus
1st Species Megalograptus welchi
2nd Species Megalograptus alveolatus
3rd Species Megalograptus ohioensis
4th Species Megalograptus shideleri
Other attributes
Time Range 449.5-443.8 mya
Location United States of America
Name Meaning Giant writing
Physical Dimensions 1.2 meters long
Dietary Classification Carnivore

Megalograptus is a megalograptid eurypterid merostomate arthropod from the Late Ordovician of the United States of America. It was named in 1874 by Hugh Miller. It was one of the earliest eurypterids, and was confused for being a graptolite, right before people discovered that it was a eurypterid.


Megalograptus had a build very similar to generic eurypterids, with a rounded cephalothorax, large eyes, long arms, a pair of paddles for swimming, and a long tail ending in a fork-like telson (also used for swimming). However, it had a few major differences; for example, it had 2 regular pairs of walking instead of 4 (the 1st and 3rd pair were vestigial), and instead of regular eurypterid claws, it had extended, spiny arms that were capable of folding. Its body would have been covered in a hard, chitinous exoskeleton.


Megalograptus was a predator, preying mainly on fish, trilobites, small orthoconic cephalopods, smaller eurypterids, and other small invertebrates. The many spines on its arms were long and pointy; along with the ability of the arms to fold, this would help it grab onto struggling prey (with an even lower chance of its meal escaping).


Megalograptus's long, spiny arms were used for catching fish, trilobites, and other small animals, as well as snagging worms out of the sandy seafloor; in . It is often assumed that it would have used its big arm spines to feel the sand and mud, detecting any prey in the way; however, eurypterids that rake through the sediment to catch prey are not very visually-oriented, as opposed to Megalograptus itself, which had large, forward-facing eyes on its cephalothorax (thus making it very visually-oriented). Like all eurypterids, Megalograptus had a telson (last segment in an arthropod tail); although Megalograptus' telson bore a slight resemblance to a large pincer, it was not used for capturing prey, and it would have used its arms to rip its prey apart. Its telson was most likely used alongside its paddles to propel it through the water.

In popular cultureEdit

Megalograptus was featured in the 1st episode of the 2003 documentary Chased by Sea Monsters, where it is shown as holding middle ground in the food chain, being bested by Cameroceras. As well as this, it was shown as behaving similarly to horseshoe crabs, stepping out of the sea to mate and lay eggs.

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