Monster evolution theory

Wyverns: Similar to the dragon these creatures evolved in a normal way but had a breakthrough during the predatory times. These lizards evolved shells that could protect from the more dangerous predators such as ancient fanged wyverns and brute wyverns. The shells were still not enough and over time grew bigger and evolved wings. But while this happened above ground creatures even older than Zhegrus grew wings too, but left to live in the caves were unlike the other wyverns they didn't need shells. soon after wyverns became more wide spread and took over the title of main monster.

Leviathans: These creatures started off from the wyvern family but like real life mosasaurs took to the sea. Instead of front arms or wings, they grew fins which made them rulers of the sea along with a few other species.

Fanged wyverns: These creatures also evolved from a relative of the wyverns but became the first mammal like reptiles in monster hunter history. Unlike wyverns these creatures stayed four legged becoming more adaptable to land than most other species.

Piscine wyverns: These species are technically fish but evolved from the commonly known lung fish. These creatures were very settle until both leviathans and elder dragons took to sea. This time mean they had to grow bigger and more powerful to compete with such strong creatures, but in one of the great seas of monster hunter a severe drout went on and land changes lowered sea levels completely thus still giving time for these tricky creatures to evolve to such changes and evolved a special type of scale to keep them from drying out. Soon before the Old ddesert made its appearence these wyverns learned to swim in sand after flopping about to get to other water sources nearby.

Fanged beast: More of the futuristics of them all these creatures evolved to mammals after the furry breakthrough of fanged wyverns in a similar manner to today mammals from mammal like reptiles.

Elder dragons: Some dragons are not technically dragons but still own up to there title. These creatures evolved from a similar fish to the celeocanth but instead of five fins they had six. They soon became the world wide famous basilisk lizard (not to be confused with the mythical or the real life basilisk lizard) having six limbs. the front limbs were only used to grab thus being a very clumsy monster although strong was still very weak. It evolved wings soon later from there pointless arms and also grew shells for protection. Also they had a good elemental advantedge like the fanged wyverns, and is know questioned if dragons are slowly losing there elemental powers becuase of there high adaptation to land and sky making them really tough.

I will add more tomorrow morning if I get the chances thanks :D