Halosaurs are eel-shaped fishes found only at great ocean depths. As the family Halosauridae, halosaurs are one of two families within the order Notacanthiformes; the other being the deep-sea spiny eels, Notacanthidae. Halosaurs are thought to have a worldwide distribution, with some 17 species in three genera represented. Only a handful of specimens have been observed alive, all in chance encounters with Remotely operated underwater vehicles.
The term "halosaur" refers to the type genus, Halosaurus, which is a Greek compound word, hals meaning "sea" and sauros meaning "lizard". Halosaurs have a spotty fossil record, the oldest known genus being Echidnocephalus from the Late Cretaceous strata of Westphalia, Germany, and the second-oldest known genus, Laytonia, from Miocene strata of California and Oregon. The fossil specimens already bear strong resemblance to the modern genera. The halosaurs' greatly elongated bodies end in whip-like tails; their scales are large. One small dorsal fin is close to the sharply pointed, mostly scaleless head. The tail fin is greatly reduced, with the anal fin being the largest fin. Their pectoral fins are slender and greatly elongated. Their mouths are somewhat large, with the lower jaw shorter than the upper jaw. The swim bladder is absent in all known species, except for Aldrovandia oleosa, which has a very small bladder.[2]
The largest species, the 90-cm (3-ft) long abyssal halosaur (Halosauropsis macrochir) is also one of the most deep-living fish, recorded at depths of 3,300 m (11,000 ft). Halosaurs have developed certain adaptations to life at these extreme depths, where no light penetrates. Their lateral line system enabling the detection of vibrations in the water is highly developed; the pores run the length of the fish's body. Some species are also known to hold their elongated pectorals erect and forward, possibly providing a further means of detection.
Halosaurs are benthic fish, spending their time cruising over or resting on the sea floor, where temperatures may be just 2-4 °C. They propel themselves with rhythmic, lateral undulations of their bodies, not unlike sea snakes. Halosaurs are thought to prey mainly on benthic invertebrates, such as polychaete worms, echinoderms, and crustaceans such as copepods, but they may also consume small fishes and cephalopods.
In life, most halosaurs are grey to bluish-black in colour. Like other notacanthiform fish, halosaurs are able to regenerate their tails easily if lost. This adaptation can be likened to certain terrestrial reptiles, such as the glass lizard, which sacrifices its tail to evade predators.
^"Part 7- Vertebrates". Collection of genus-group names in a systematic arrangement. Archived from the original on 5 October 2016. Retrieved 30 June 2016.
^Aldrovandia oleosa, a New Species of the Halosauridae, with Observations on Several Other Species of the Family
Halosaurs are eel-shaped fishes found only at great ocean depths. As the family Halosauridae, halosaurs are one of two families within the order Notacanthiformes;...
The abyssal halosaur (Halosauropsis macrochir) is a species of bottom-dwelling, deep-sea fish in the family Halosauridae that is found in all oceans at...
The goanna fish, Australian halosaur, or common halosaur, Halosaurus pectoralis, is a halosaur of the genus Halosaurus, found in the south west Pacific...
Echidnocephalus troscheli is an extinct, prehistoric halosaur. Fossils are found from Campanian strata of Westphalia, Germany. The complete and incomplete...
biomass. Other species include deep sea cods (morids), deep sea eels, halosaurs and notacanths. Benthopelagic sharks, like the deep sea squaloid sharks...
Forey et al. 1996 (bonefishes) Order Notacanthiformes Goodrich 1909 (halosaurs and spiny eels) Order Anguilliformes Jarocki 1822 sensu Goodrich 1909...
Aldrovandia phalacra, the Hawaiian halosaurid, is a species of ray-finned fish in the family Halosauridae. It is a circumglobal species found at bathyal...
Laytonia is an extinct genus of prehistoric halosaur that lived in deep water off the North American Pacific Coast from the Zemorrian Epoch (comprising...
Aldrovandia gracilis, also known as the gracile halosaur, is a species of ray-finned fish in the family Halosauridae. It is found in the north west Atlantic...
Halosaurus johnsonianus, also called the Sahara halosaur, is a deep-sea fish in the family Halosauridae. It is found in the eastern Atlantic Ocean from...
Order Albuliformes, the bonefishes Order Notacanthiformes, including the halosaurs and spiny eels Order Anguilliformes, the true eels Order Saccopharyngiformes...
Halosaurus ovenii, also called the Oven's halosaur, is a deep-sea fish in the family Halosauridae. It is found in the eastern Atlantic where it is widely...
This is a list of the fish species found in India and is based on FishBase. Albula vulpes translated "Thapi_Lesapo" by Mr Jasson Kemiso Mudongo, a young...
Order Albuliformes, the bonefishes Order Notacanthiformes, including the halosaurs and spiny eels Order Anguilliformes, the true eels Clade Osteoglossocephala...
Order Albuliformes, the bonefishes Order Notacanthiformes, including the halosaurs and spiny eels Order Anguilliformes, the true eels and gulpers Order Saccopharyngiformes...
troscheli is an extinct, prehistoric halosaur. Fossil specimens suggest an animal already looking very much like modern halosaurs. †Egertonia Late Cretaceous-Eocene...
examples include the jellyfish Stellamedusa ventana and the eel-like halosaurs. In the US, cutting-edge work is done at several public and private oceanographic...
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