[3] The only known fossil genus is Carpathichthys from the Early Oligocene of Poland, although an undescribed species of Bathyprion and several indeterminate taxa are also known from the same formation.

They are shaped in an eel-like elongation, with large eyes, gill rakers that range from moderate to long and numerous, and spineless fins.

[6] Their early life development is from large eggs directly into yolk sac juveniles that travel in deep waters.

[10] Vertical shift could occur due to predation being higher close to the sea floor and/or warmer water having a larger abundance of plankton.

Juvenile slickheads may have a preference to travel upwards to take advantage of the lack of predation and abundance of food to increase survival rates.