"The flowerjaw body plan reached its peak diversity in marine environments, where this group inhabits almost every major ecological niche. The deep oceans, while low in energy and deprived of oxygen and sunlight, are nevertheless home to numerous creatures. The beings of this ecosystem are able to exploit the abundant surface environment through either migrating vertically at night to feed, or by preying on creatures migrating into the deep to escape surface predators.
Sit and wait predation is an energy efficient way to hunt, and the Crystalline Cloakmouth represents an extreme adaptation to this way of life.
The reduced, soft body hangs below the highly modified mouthparts, which are dominated by huge vertical jaws spanning 13 inches from tip to tip. Sharp semitransparent mandibles are poised ready to snap shut on any prey lured inwards by the bioluminescent tip of the tongue. Prey that comes too close is skewered by the mandibles and then enclosed by the heavily pigmented jaws. This prevents they preys' defensive bioluminescence being detected by larger foes.
The two huge lower eyes are oriented upwards and modified to detect the bioluminescence of prey, or their shadows' against the downwelling surface light. The horizontal jaws, thin and elongated, are spread to the sides and covered in a line of fluid filled spheres able to detect vibrations in the water, a system also present around the rim of the main jaws. The horizontal mandibles are shorter and more robust than the crystalline seizing jaws, and are hidden away until prey is captured, which they proceed to butcher and then pass downwards into the pharynx.
The upper eyestalks are highly elongated and the post-ocular sections bifurcated into sensors adapted to detect the sex pheromones of conspecifics. Currents are so slow and the environment so vast that highly sensitive antennae are needed to detect minute concentrations of chemicals in the water. The small eyes on these tentacles are still functional but of low resolution; they monitor the light from the surface world and allow the Crystalline Cloakmouth to tell night from day.
Although ungainly, the Crystalline Cloakmouth can move quickly in short bursts to escape predators. Defence consists of several stages: First, the jaws with their large surface area are clamped rapidly together, shooting the creature away in the opposite direction. At the same time, thin translucent threads are extruded from modified limbs near the tail to form a mesh in the fleeing animals' wake. Predators caught in this are tangled by the sticky threads, which bioluminesce on contact and thus render the predator visible to its own enemies. Proteins on the Cloakmouths' skin inhibit this reaction when it becomes entangled in its own threads. As a final defence, the Crystalline Cloakmouth leaves the area using paired fins usually held tightly against its body, swimming slowly backwards to new hunting grounds. "
The informative description of the work is so believable that one could learn a lot of real world biology from it. For instance, it describes how the Cloakmouth comes close to the surface at night, which is exactly what real world deep sea creatures to.
And at the same time even our own deep sea has plenty of strange and alien-looking creatures (all of them discovered only in relatively recent years and many more possibly yet to discover), to the point even something like this seems like something we can discover there one day