Aside from the pisceans and the selachians how many other mers are there? maybe seal mers or octopus mers or even crustacean mers?
Anon, you opened a can of worms fish. Here is a portion of my Encyclopedia Nautica, which I began back in 2002 and have been building on ever since:
Pisceans - Fish folk, more bendy tails and semi-transparent fins (classic Little Mermaid look), scales instead of skin. Most prolific mers of the sea with many sub-species and variations in tail shape and color. Most lay eggs (oviparous), though a few give birth to live young (viviparous). Large extended families are called shoals, though some have adopted the term “pod” to describe their social units
Delfins - Dolphin folk, powerful tails and thick fins, possessing skin, not scales. They give birth to live young and have complex social structures and families (pods)
Serpenians - Sea snake folk, long ribbon-like tails. Ovoviviparous, meaning they carry their young as eggs which hatch in utero and are then born
And then there were the Serpenians, the sea snake people, who lived in the shadows and on the fringes of civilized society. Of all the merfolk, they and their cousins, the Muray, or eel people, were considered the most wild and dangerous, their ways heathen and arcane, their bites rumored to kill, and rumored to possess magic powers
Cetaceans - Whale folk (technically Delfins are classified as cetaceans as well) with dorsal fins and species-specific flukes
Selachians - Shark folk, dorsal fins and vertical tail fins. Depending on the sub-species, they may lay eggs (oviparous), give birth (viviparous), or do both (ovoviviparous). Unjustly rumored to be vicious, aloof, gluttonous barbarians who sometimes committed acts of cannibalism against their own (or other merfolk)
Carcarins - My old term for shark folk. But not all sharks are of the carcharodon genus, so I decided to go with the broader term “selachian”, from the superorder Selachimorpha
Sirenian - The first mer species I coined back in 2002, though I’m sure others have thought of this name as well. Sirenians have very long, thin, snake-like tails and large flowery fins, and scaly, aquatic ears. The only mer species capable of enchanting humans with their songs as well as being the species closest to humans, literally and biologically
Cephalopeans - The genus that contains such mer species as Nautilans (squid folk) and Octopians (octopus folk)
There were the Nautilans and the Octopians, all part of the greater clan of Cephalopeans. They possessed tentacles instead of tails and were known for being very intelligent and incredibly shy. As a result, they often found themselves ostracized from the rest of the merfolk for being “strange”, and they faced discrimination for not having fins. But such bias against Cephalopeans is unheard of in these modern times
Sygnathians - Seahorse folk
There were the Syngnathians, who had bony, backward-curving tails and were a very cheerful and small-sized people. Their defining trait was that their reproduction worked in the opposite direction: the females would pass their eggs to the males through a special tubelike organ and the males would become pregnant and give birth to their offspring. It was a pleasing arrangement for them, even though other merfolk found it peculiar
Like in real-life nature, gender is very fluid in these AUs. Males can morph into females and vice versa, males can give birth, females can inseminate, and dual-sexes are common. It’s a GNC rainbow paradise down here
