Halosauridae
| Halosaurs Temporal range: Late Cretaceous to present |
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|---|---|
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| Aldrovandia sp. | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Notacanthiformes |
| Family: | Halosauridae |
| Genera | |
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Aldrovandia |
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Aldrovandia
Halosauropsis
Halosaurus
†Laytonia
†Echidnocephalus
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 gas bladder is absent.
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