Twilight Arrowhead

Evolving rather closely alongside its surface dwelling cousin, the twilight arrowhead features much of the same internal features and anatomy as their ancestors, from which they have split. Differences, however, do exist. For one, they are capable of producing clicks by smacking their tusks against the sides of their head. The sharp sound produced bounces off distant objects, and the sightless twilight arrowheads will then detect the returning vibrations in order to aid them in navigating through water, in a matter not unlike a weak form of sonar. This complements both their chemosensory senses as well as their primitive capacity to detect bioelectric signals.

Adults have small, notably thinner patches exoskeleton along their sides where they can form small bioelectric currents and - unintentionally - flashes of light so that they may more effectively communicate with one another. This light come about by sudden retractions of muscles visible through the chitin, which is intended to produce a bioelectrical signal but also forces oxygen into the regions. Luciferin-like compounds, present in the flesh, are triggered by this sudden flush of oxygen to begin undergoing luminescence. In the darker depths of the ocean, and with le need to compete against surface currents, the twilight arrowheads are not as powerful a swimmer as their surface-dwelling kin, but this has not proved evolutionarily disadvantageous for them as their are fewer predators in the regions they inhabit with which they would need to deal with.