Notacanthiformes

(vertebrate zoology) An order of actinopterygian fishes whose body is elongated, tapers posteriorly, and has no caudal fin.

An order of actinopterygian fishes known also as the Heteromi (spiny eels or notacanths) and the Lyopomi (halosaurs). The body is elongated, tapers posteriorly, and has no caudal fin (see illustration).

Spiny eel (Notacanthus nasus). (After D. S. Jordan and B. W. Evermann, The Fishes of North and Middle America, U.S. Nat. Mus. Bull. no. 47, 1900)

This small order, which has a history extending back to the Upper Cretaceous, includes 3 families, about 8 Recent genera, and about 25 species. Spiny eels and halosaurs inhabit deep seas of all oceans; some have photophores. They are like true eels (Anguilliformes) in that they lack a firm suspension of the pectoral girdle from the skull, but some have fin spines like the perciform fishes. See also Actinopterygii; Anguilliformes; Photophore gland.

Notocanthiformes Fossil range: Late Cretaceous–Recent PreЄ Є O S D C P T J K Pg N [1]
Snubnosed Spiny Eel, Notacanthus chemnitzii. From plate 50 of Oceanic Ichthyology by George Brown Goode and Tarleton Hoffman Bean, published 1896.
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Notacanthiformes
Families
Halosauridae Notacanthidae

Notacanthiformes is an order of deep-sea ray-finned fishes, consisting of the families Halosauridae and Notacanthidae (spiny eels)

The order is of relatively recent vintage; Fishes of the World lists it as a suborder Notacanthoidei of Albuliformes. The notacanthiforms are much more eel-like than the albuliforms; for instance, the caudal fin has disappeared.

Fish of the order are found in oceans worldwide, at depths from 120 metres (390 ft) to 4,900 metres (16,000 ft). They are elongated fish, although not as much so as the true eels. They typically feed on slow-moving or sessile animals, such as molluscs, echinoderms, and sea anemones. Like the true eels, they have a leptocephalus larva that floats in the surface waters before transforming into an adult. Unusually, the larva can often be larger than the adult.^[2]

References

1. ^ "Notacanthiformes". FishBase. Ed. Ranier Froese and Daniel Pauly. January 2009 version. N.p.: FishBase, 2009.
2. ^ McCosker, John F. (1998). Paxton, J.R. & Eschmeyer, W.N.. ed. Encyclopedia of Fishes. San Diego: Academic Press. p. 86. ISBN 0-12-547665-5. 

• "Notacanthiformes". FishBase. Ed. Ranier Froese and Daniel Pauly. January 2006 version. N.p.: FishBase, 2006.
• Joseph S. Nelson. Fishes of the World. John Wiley & Sons. ISBN 0-471-54713-1. 

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