Question 1

How do you say Megarachne?

Accepted Answer

Megarachne is pronounced MEG-ah-RAK-nee, with the stress on the third syllable RAK. A good trick is to say the word mega, then add rack-knee at the end: mega-RACK-knee. The name comes from Ancient Greek, so the ch makes a hard k sound rather than a soft ch sound like in the word cheese. Once you hear it a couple of times, it sticks pretty fast.

Question 2

What does Megarachne mean?

Accepted Answer

Megarachne means great spider in Ancient Greek. The mega part means great or large, which is the same prefix used in words like megaphone and Megalosaurus. The rachne part comes from arachne, the Greek word for spider, which is also where the word arachnid comes from. The name was chosen in 1980 because scientists at the time thought they had found the biggest spider ever, though they later discovered it was not a spider at all.

Question 3

Was Megarachne really a giant spider?

Accepted Answer

No, and this is one of the greatest plot twists in paleontology. When paleontologist Mario Hünicken described Megarachne in 1980, he genuinely believed the fossil was a giant prehistoric spider with a body span of about 34 cm, which would have made it the largest spider ever known. For over 20 years, that story appeared in books and magazines. Then in 2005, researchers led by Paul Selden examined new fossil material and proved conclusively that Megarachne was actually a eurypterid, a kind of extinct aquatic arthropod more closely related to horseshoe crabs than to spiders.

Question 4

What actually is a eurypterid?

Accepted Answer

Eurypterids are an extinct group of aquatic arthropods that lived from roughly 450 to 252 million years ago, and they are sometimes called sea scorpions, though many species like Megarachne actually lived in freshwater. They were distant relatives of modern horseshoe crabs, spiders, and scorpions, and many were fierce predators with powerful clawed appendages. Some eurypterids grew to enormous sizes, with the largest, Jaekelopterus, reaching nearly 2.5 meters in length. Megarachne belongs to a subgroup called Stylonurina, which were mostly bottom-walkers rather than active swimmers.

Question 5

How big was Megarachne?

Accepted Answer

The original 1980 estimate suggested Megarachne had a body span of around 34 cm (about 13 inches) if it were a spider, which would have been enormous. After the 2005 reclassification as a eurypterid, researchers could make more accurate size estimates based on its actual body plan, placing it as a moderately large eurypterid. The fossils come from the Bajo de Veliz Formation in Argentina and are fragmentary enough that precise size estimates remain somewhat uncertain even today.

Question 6

Where did Megarachne live?

Accepted Answer

Megarachne lived in what is now the San Luis province of Argentina, in a freshwater environment that existed approximately 298.9 million years ago during the Late Carboniferous period. The fossils were found in the Bajo de Veliz Formation, a rock deposit that preserves the remains of an ancient lake or river system. Back then, Argentina was part of the supercontinent Pangaea, and the climate in that region was very different from the dry, rugged landscape of San Luis province today.

Question 7

Why did scientists think it was a spider in the first place?

Accepted Answer

The original fossil material of Megarachne was fragmentary, meaning scientists were working with incomplete pieces rather than a complete skeleton. Certain features of eurypterid anatomy, particularly when viewed in specific orientations in rock, can look surprisingly similar to spider features when only partial remains are preserved. Mario Hünicken made an honest scientific mistake based on the evidence available to him in 1980. It was not until 2005, when Paul Selden and colleagues examined new and better-preserved specimens from the same Argentine formation, that a proper comparison could be made and the eurypterid identity confirmed.

Question 8

If Megarachne is not the biggest spider ever, what is?

Accepted Answer

After Megarachne was reclassified in 2005, the title of largest known prehistoric spider shifted to other candidates. Mongolarachne jurassica, a true spider discovered in Jurassic deposits in China, is currently considered one of the largest fossil spiders ever found, with a body length of about 2.5 cm and leg span estimates around 15 cm. For comparison, the largest living spider today is the Goliath birdeater tarantula, which can have a leg span of up to 30 cm. So even the biggest real prehistoric spiders were not nearly as dramatic as Megarachne was once rumored to be.

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