Merfolk

Merfolk are a branch of elves that split during the Age of Legends. They evolved quickly from secondary gills and webbed digits to a full tail in place of their legs. They can venture above the water for short periods of time as long as they remain moist.

A merfolk has the upper torso of an elf and the lower half of a fish.

The skin of merfolk is always moist to the touch and slightly less pliable than their terrestrial species. Instead of being nearly hairless like elves, merfolk upper bodies are covered with a very fine hair which helps keep their upper body warm.

The eyes of merfolk are unique among species on Miranda. They look very close to other elves with the exception of a second nictating eyelid and bioluminescence ring around the outside of their iris. This ring is barely visible in sunlight, only giving the eye a natural sparkle, but in the cold and darkness it illuminates the entire eye. This illumination is a magical effect that allows the merfolk to see hundreds of feet even at the deepest depths are clear as a moonlight night above the water.

Split Tail

A strange anomaly that occurs once per thousand births is a merfolk with a split-tail. The merfolk will have legs as their ancestors, but instead of feet they have longer and flexible fins. These merfolk are unable to swim as efficiently as typically live in shallower waters and estuaries.

Merfolk, like nearly all sapient species on Miranda, are live births. A mermaid (female merfolk) will become fertile once every ten years and remain fertile until around one-hundred and eighty (180 years menopause). Mermaids carry their young for ten (10 pregnancy) months. Multiple births are very rare and never are more than twins. Mermen will be sexually mature by their twentieth year (20-22 male sexual maturity) and fully physically mature by their fortieth (40-42 male physical maturity), while mermaid are sexual and physical maturity in their thirties (30-32).

Most merfolk will not reach their elderly years until past their second century and show little signs of aging until then. The average lifespan of a merfolk is about two-hundred and fifty years (250 average lifespan)

Equatorial

As per above

Arctic

The arctic merfolk differ physically from their equatorial cousins. Their upper bodies are covered in hair far thicker and courser than any other elf. In addition their tail fin is turned vertically and the edge of the tail extends nearly up to the point where their fish-body begins on their backside.

Arctic merfolk are also shorter and with thicker chests to account for the additional fat they carry. It could also be accountable to the foods that she eat, which are higher in fats.