Alien Race (physiology)

Physiology - Body Structure
Above the waist, they are generally humanoid, however with a more willowy figure. Below the waist, they resemble a cross between a tadpole and sea lion. That is, they follow the general shape of a sea lion, however thinner, and with the upper and lower fins similar to a tadpole. They have 4 flippers, all of which can function as legs as well as for swimming.

They have several gill slits along their tail, acting as jet propulsion, as well as a way to exhale while breathing underwater.

Below the elbow, their arms are slightly flattened and oar-like. Their hands typically have five fingers.

While appearing mainly aquatic, they are amphibious, and can breathe both water and air. They spend roughly equal time in land and sea, though preferring sea slightly more. When it comes time to mate, they bury eggs in the sand and one parent watches over them while the other hunts.

Physiology - Head
Perhaps their most striking feature besides their mermaid tail and bright skin is the fact that they have two to three tails sprouting from their skull, reaching down to their waist. It is used as a super-sensitive antennae for detecting faint smells, air vibrations, and electromagnetic pulses. It is also used in fat storage, similar to a camel’s hump.

The Red People and Green People have three head-tails (two on side; one on back) which are the same colour as their horns. The Blue and Grey People have two head-tails, both in back, which are the same colour as their skin.

They have two rows of teeth on each jaw; 128 total. The front row is sharp and needle-like, while the back teeth are broad and flat. The back teeth are half the height of the front teeth, making it easier for their teeth to interlock.

While their facial features are mainly humanoid, their eyes are 10-15% larger and slightly almond-shaped. Their iris takes up most of the space such that the sclera isn’t visible. Their pupils are also rather large.

Physiology - Internal Structure
They have three stomachs, designed to digest still-living prey. The first stomach is little more than a carrying case, to hold something before actually digesting it. It is filled with a sedative so living prey can’t damage them or try to escape. The second stomach is the actual stomach, filled with acid and intended to break apart food. The third stomach is little more than a shortened intestine; it gains materials from digested food by holding them inside it for a long amount of time rather than by pushing them through twenty feet of useless bowel.

It is hypothesized that, in early evolution, it was easier to simply sneak behind and swallow prey without killing them --similar to a gulper eel. However, this method rarely sees use, as most food is cooked before consumption. That said, some small animals are still eaten alive as a delicacy.

Replacing what would be their left lung is an internal gill structure. They have two throats to accommodate both the lung and the gill; and when they are on land/in water the unnecessary throat will automatically close. Both have a larynx, albeit one adapted for use in water, allowing them to talk underwater.

Their heart is 25% larger than that of a human’s, and placed right below the lung. It is a basic 4-chambered heart, similar to that of a human’s. However, each chamber resembles a flattened teardrop and are stacked on top of each-other, originating from one point. 

Physiology - Subspecies
Blue People: Evolved in shallow waters and reefs. As dexterity is not much of an issue, their fingers are webbed like a frog’s. They have evolved light blue skin as the shallow water ensures no predators will be above them, and no other angle will silhouette them in the ground. Green People: Formed in the kelp forests. Their hands are very dexterous, allowing easy manipulation of kelp plants. Their skin is a jade green, blending in with the surrounding kelp. Their front row of teeth is not as sharp as the other subspecies, and while they are omnivorous, prefer plant matter. Their flippers resemble broad kelp leaves. They have two small (about the same height as their head) antelope-like horns used for self-defense and mating disputes.
 * Skin = #1A486A.
 * Eyes = #FEEC40.
 * Skin = #1D673C.

Red People: Born in the bloodgrass plains. While their skin is red with white markings, their head-tails are white with blue markings. They also have two large (about 1.5 the height as their head) antelope-like horns on the crest of their head, for self-defense or mating disputes. Grey People: They grew in dark caves and nocturnal environments. Their skin is darkened to match the rock or dark waters, and their eyes are more capable in darkness than the others. They are also capable of passive echolocation. Their flippers resemble insect wings and are used similarly to a cat's whiskers, allowing them to feel their way around in darkness.
 * Horns = #E7E7E7
 * Horn markings: #2D2D24
 * Eyes = #FEB63A
 * Skin = #601818.
 * Horns = #E7E7E7
 * Horn markings: #2D2D24
 * Eyes = #FDA73F.
 * Skin = #284C46.
 * Eyes = #A31090