It can also possess bright yellow pelvic and caudal fins, especially during spawn.
The mantle narrows towards the back and possesses large terminal fins.
They were probably relatively good swimmers, possessing dorsal fins, paired pectoral fins, and a strong tail.
A group related to the Exocoetidae, one or two hemirhamphid species possess enlarged pectoral fins and show true gliding flight rather than simple leaps.
Relative to its mantle size, it possesses larger fins and arm suckers, the latter being predominantly arranged in two rows.
Many extinct cephalopod groups also possessed fins.
Grimalditeuthis and larval Chiroteuthis are unusual in that they possess a pair of flotation devices or "secondary fins" attached to the tail.
Although it emerged over 300 million years ago, Deltoptychius was similar in appearance to modern-day chimaeras, possessing a long, whip-like tail and large, wing-like pectoral fins that it probably used to glide through the water.
In 1861 Thomas Henry Huxley had created an order: Crossopterygii to house those extinct and extant animals that possessed lungs and fleshy pectoral fins with lepidotrichia.
Clear distinguishing features among congrids are few; they all lack scales, and most possess pectoral fins.