While a fossilized creature once held the title, the biggest spider to ever exist in history, based on current scientific understanding, is the Goliath Birdeater (Theraphosa blondi).
The Case of Megarachne servinei: A Historical Misidentification
For many years, the fossilized remains of Megarachne servinei, discovered in the Permo-Carboniferous Bajo de Véliz Formation of San Luis Province, Argentina, were believed to represent the largest spider that ever lived. This massive arthropod, with a described body length of 339 mm (approximately 13.3 inches), was initially identified as a giant mygalomorph spider, akin to a tarantula. Its immense size led to its widespread recognition as the largest known spider to have graced Earth.
However, subsequent in-depth research and re-examination of the fossil revealed a different truth. Megarachne servinei was reclassified not as a spider, but as a type of extinct aquatic arthropod known as a eurypterid, or "sea scorpion." This re-evaluation corrected a long-standing misconception, meaning that despite its impressive size, Megarachne servinei does not hold the record for the biggest spider.
The True Giant: The Goliath Birdeater
Currently, the undisputed title for the biggest spider by mass and body size belongs to the Goliath Birdeater (Theraphosa blondi). Native to the rainforests of South America, particularly regions of Suriname, Guyana, French Guiana, northern Brazil, and southern Venezuela, this colossal tarantula is a formidable creature.
Key characteristics of the Goliath Birdeater include:
- Size: Its body alone can reach lengths of up to 13 cm (5 inches), but its leg span can extend to an astonishing 30 cm (12 inches) – roughly the size of a dinner plate.
- Mass: Adult Goliath Birdeaters can weigh over 170 grams (6 ounces), making them the heaviest spiders in the world.
- Diet: Despite its name, the Goliath Birdeater primarily preys on insects, frogs, lizards, and small rodents. While it is capable of eating small birds, this is not its primary food source.
- Habitat: These spiders are terrestrial, living in deep burrows in the forest floor, often lined with silk.
- Defense Mechanisms: When threatened, the Goliath Birdeater can flick urticating hairs from its abdomen, which can cause irritation to predators. It also has large fangs capable of delivering a bite, though its venom is generally considered mild to humans, similar to a bee sting.
Comparative Overview of Giant Arthropods
To better illustrate the scale, here's a comparison between the historical misidentification and the actual largest spider:
| Feature | Megarachne servinei (Reclassified) | Theraphosa blondi (Goliath Birdeater) |
|---|---|---|
| Classification | Eurypterid (Sea Scorpion) | Spider (Tarantula) |
| Era | Permo-Carboniferous (Ancient) | Modern (Still exists) |
| Origin | Argentina | South America |
| Body Length | Up to 339 mm (13.3 inches) | Up to 13 cm (5 inches) |
| Leg Span | N/A (not a spider) | Up to 30 cm (12 inches) |
| Weight | N/A (not a spider) | Over 170 grams (6 ounces) |
While other large spiders exist, such as the Giant Huntsman Spider (Heteropoda maxima) which boasts the largest leg span among extant spiders, the Goliath Birdeater remains the most massive and therefore holds the title of the "biggest spider" based on overall body size and weight.
