The most diverse clade of vertebrates to ever exist, changelings or metamorph birds range in size from a few millimeters to tens of meters in length. They exist in every environment Serina can offer and include the biggest flying birds and smallest ever birds to have evolved. A complex evolutionary history involving the evolution of free-living larval offspring, born at an extremely early developmental stage, has effectively reset the evolution of this clade to a basal template. Marsupial-like young with poorly-formed skeletons at hatching allowed these birds to evolve soft-shelled and increasingly small eggs, and allowed them to reform their bodies in ways impossible for other bird groups which hatched at a more specialized level of development. Metamorphs by the Ultimocene include insect-like parasites, gigantic megafauna, fully-aquatic sea animals, and almost everything in between.
As of 2023, most Serinan animals have up-to-date family trees visible here!