The cave xxeljet split from its ancestor, the polar xxeljet. There they grew to twice its ancestor's size but had to have a more stout shape to retain heat. It still has the anti-freeze-like chemical in its blood stream to keep it from freezing. It can still filter feed but mostly feeds on the abundant icecave swarmers which are latched on to the cave walls. Their jaws have gotten larger and have bigger teeth to strike and bite them.
Like its ancestor, it has a methane producing chamber which is not only used for buoyancy when swimming, but can be used as a jet when escaping predators. The methane is produced as a by-product of digestion. Their compound eyes have now adjusted to seeing in the even fainter light in the caves.
Living Relatives (click to show/hide)
These are randomly selected, and organized from lowest to highest shared taxon. (This may correspond to similarity more than actual relation)
