Arthropleura holds the record as the largest known arthropod, reaching over 2.6 meters (8.5 feet) in length and an estimated weight of 50 kg. [1, 13, 14] Another giant, the sea scorpion Jaekelopterus rhenaniae, was estimated to be 2.3-2.6 meters long. [21] Giant dragonflies like Meganeura boasted wingspans of up to 75 cm. [2]