Homo mermanus - Young Justice: Phantoms

The descendants of both Vandar Adg (the first Homo meta) and Arion (the first Homo magi), Homo mermanus were born during the horrific cataclysm that destroyed their home, the continent of Atlantis. 

Undergoing extreme psychological and physical distress, the devastated remnants of the Homo magi developed the ability to breathe underwater when their latent meta-genes were forcibly activated, leading to their eventual evolution into the modern-day Atlanteans. 

Homo mermanus continued to expand across the seven seas, till at last the new kingdom of Atlantis controlled 3/4ths of the Earth. 

Homo magi - Young Justice: Phantoms

The direct descendants of Arion, Lord of Atlantis, the Homo magi were a subspecies of meta-humans (Homo meta), who could perform incredible magical feats. This was due to their progenitor's prolonged exposure to the magical Circlet of Order, an artefact gifted to Arion by the Lords of Order.

These magical beings lived in harmony with both Homo meta & sapiens and thrived in Atlantis. Their presence helped the once-small settlement grow into the capital of the entire Atlantean continent.

Almost all Homo magi were wiped out when The Lord of Chaos Klarion submerged Atlantis, killing millions. However, a handful survived when their meta-genes activated from the intense psychological pain and trauma of the ordeal. This event led to the birth of yet another new species, the water-breathing Homo mermanus; more commonly known in the 21st Century as the Atlanteans.