Eurypharynx pelecanoides is a species of deep-sea marine eel in the family Eupharyngidae with an extraordinarily large expanding mouth, extremely long jaws containing numerous small teeth, a large distensible abdomen, and a long, tapering compressed tail. The cranium is very small relative to the body. (Nielsen 1989). The black scaleless body, relatively longer jaw, smaller abdomen, smaller gill openings which are closer to the anus than the snout, minute teeth and pectoral fins, and more anterior origin of the dorsal fins distinguish the Pelican Eel from the related saccopharyngid eels (eupharyngids and saccopharyngids are both known as “gulper eels”). Mature males undergo a morphological transformation that makes the head appear notched in dorsal view (Charter 1996). The shape and use of the mouth of E. pelecanoides gave rise to the common name Pelican Eel (this species is also known as Umbrellamouth Gulper).
For most of the 20th century, this was considered to be a rare deep-sea fish, but in recent decades hundreds of specimens have been taken, mainly in the Atlantic Ocean. Specimens have ranged from 90 to 620 mm in length. Complete specimens are rarely found. The long, slender tail, the long jaws ,and the soft buccal and abdominal skin tend to become entangled and torn in nets. Most specimens that have been examined have lost part of the tail, but the preanal length is almost always obtainable and there is a clear linear function between preanal and total lengths. Thus, an approximate total length can be estimated if the preanal length is known. The Pelican Eel has been reported from temperate and tropical regions of all oceans. In the eastern Pacific, it is known from northern California to Peru. In the Atlantic, it is known from off Iceland (65°N) to 48°S. It is believed to occur at depths ranging from 3000 to 500 m. Analysis of the stomach contents of specimens indicates that the diet includes crustaceans, fish, Sargassum seaweed, cephalopods, chaetognaths, pelagic tunicates, scyphozoans, and nemerteans. (Nielsen 1989) Most bony fish are "gape and suck” feeders, sucking food into the mouth by creating a sudden negative pressure in their orobranchial cavity. In these cases, the fish remains more or less stationary while food and surrounding water move into the gape. However, the morphology of the Pelican Eel’s skull and jaws do not permit a sudden expansion of the enormous buccal cavity. Nielsen (1989) describes a hypothesized alternative thrusting method of feeding, analogous to that used by a diving pelican. (Nielsen 1989)
Pelican Eels reproduce by releasing eggs that hatch into planktonic larvae. Data from Pelican Eels that have been collected suggest that females are semelparous, i.e., that they die after reproducing once (Charter 1996). Studies of the mitochondrial genome of the Pelican Eel and related fishes have revealed that eupharyngid and saccopharyngid gulper eels share a large-scale gene rearrangement relative to
other vertebrates (Inoue et al. 2003).