The Meganulons' name comes from Meganeura, a species of extinct dragonflies from the Carboniferous period approximately 300 million years ago.
Presumably, they are, like the Rodan, from the Cretaceous Period. They were reanimated by mining operations in Kitamatsu village, Kumamoto Prefecture.
HistoryRodan. They were first awakened during a nuclear, and they attacked and ate a few trapped miners. They escaped the mine and attacked a nearby village, and they captures another miner. The miner finds an egg in the cave, which hatches into Rodan. Rodan begins to eat the Meganulon until it has enough strength to escape the cave. Tokyo, and he releases it into the sewers when it starts to ooze. The egg hatches into a Meganulon, and it kills citizens of the city before turning into a Meganula.
MeganulaThe Meganula (メガニューラ?, Meganyūra) were the second form of the Meganulon. They attacked Godzilla because he was a source of energy. Godzilla managed to kill most of them, but some escaped with his energy. The flew to Tokyo and gave the energy to Megaguirus, and dying in the process.
- The Meganulon is an actual species of giant dragonfly that lived during the Devonian Period nearly 300 million years ago. Of course, the real Meganulon never reached the size of the monsters that appeared in Rodan and Godzilla vs. Megaguirus.