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'Elusive' brainless fish discovered in waters off Scotland

The prehistoric Amphioxus, described by the Scottish Government as ''elusive'', was found in waters off Tankerness in Orkney.
The fish has a nerve chord down its back and is said to be regarded as a representative of the first animals to evolve a backbone.

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Amphioxus
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The lancelets (from "lancet"), also known as amphioxi, comprise some 22 species of fish-like marine chordates with a global distribution in shallow temperate and tropical seas, usually found half-buried in sand. They are the modern representatives of the subphylum Cephalochordata, formerly thought to be the sister group of the craniates.
Lancelets serve as an intriguing comparison point for tracing how vertebrates have evolved and adapted. Although lancelets split from vertebrates more than 520 million years ago, their genomes hold clues about evolution, particularly how vertebrates have employed old genes for new functions. They are regarded as similar to the archetypal vertebrate form.

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Laccognathus embryi
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New species of ancient predatory fish discovered

The Academy of Natural Sciences has announced the discovery of a new species of large predatory fish that prowled ancient North American waterways during the Devonian Period, before backboned animals existed on land.
DRs. Edward "Ted" Daeschler and Jason Downs of the Academy and colleagues from the University of Chicago and Harvard University describe the new denizen of the Devonian they named Laccognathus embryi in the current issue of the Journal of Vertebrate Paleontology.
The 375-million-year-old beast was discovered by the same group of researchers who discovered Tiktaalik roseae, the important transitional animal considered "a missing link" between fish and the earliest limbed animals. The fossil remains of the new species were found at the same site as Tiktaalik, on Ellesmere Island in the remote Nunavut Territory of Arctic Canada.

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Phreatichthys andruzzii
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A "day", for a blind, cave-dwelling fish in Somalia, is twice as long as ours.

Most animals have an internal body clock, or circadian rhythm, that lasts around 24 hours and is modified by the light-dark cycle of a day.
But an international team, whose research is published in the open access journal PloS Biology, shows that certain blind cave fish have a circadian rhythm that lasts almost two days.
The cavefish, Phreatichthys andruzzii, has evolved for nearly two million years in the isolated darkness of caves beneath the Somalian desert.

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Jaws vs jawless: battle for the seas

400 million years ago jawless vertebrates filled the oceans but today they are limited to only a few species: boneless, parasitic creatures such as lampreys and hagfishes.
So what happened to this 'lost tribe' of ancient mariners? Were they the victims of environmental change or thrust aside by jawed newcomers? And how did fish evolve jaws anyway?

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Deep in the Silurian seas, some 420 million years ago, a strange structure had just emerged in the bodies of many new vertebrates. Some fish began developing a defined upper and lower jaw that allowed them to devour large and hard-shelled organisms.
Today more than 99 percent of vertebrates have these handy eating apparati. But new research shows that for all of their utility, mandibles did not take over the oceans in one swift chomp, as many scientists had previously assumed. Rather, the early, jawed fish didn't make too much of a dent in their jawless compatriots' success for some 30 million years. The new findings were published online July 6 in Nature (Scientific American is part of Nature Publishing Group).

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Coelacanth
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Coelacanth slowly reveals its secrets

An odd-looking ancient fleshy fish continues to serve as a reminder of just how little we know about the natural world.
In 1938, scientists discovered the coelacanth, a large primitive deep-dwelling fish that was supposed to have been long, long extinct.
The fish provided an immediate link to our dim evolutionary past, resembling the lobe-fin fish that were likely the first to leave the water and take to land, ultimately begetting the amphibians, reptiles and mammals we see today, including the human race.

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Ky. man finds shark fossil in mine

A miner has found a fossil from a shark jawbone deep in a central Kentucky mine and now it is on display at the University of Kentucky.
The fossil was found in February in Webster County, Ky., where 25-year-old miner Jay Wright was working to bolt a roof 700 feet underground. The 300-million-year-old black jawbone is believed to be from a shark from the Edestus genus that once swam the seas over what is now Kentucky.

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Prehistoric Fish Extinction Paved the Way for Modern Vertebrates

A mass extinction of fish 360 million years ago hit the reset button on Earth's life, setting the stage for modern vertebrate biodiversity. The mass extinction scrambled the species pool near the time at which the first vertebrates crawled from water towards land.
Those few species that survived the bottleneck were the evolutionary starting point for all vertebrates--including humans--that exist today, according to results of a study published this week in the journal Proceedings of the National Academy of Sciences (PNAS).

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Xiphactinus audax
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Giant fish under the hammer

A detail of a giant predatory Cretaceous period (145 million to 65 million years ago) fish, discovered in Kansas, on display before sale at auction, in Los Angeles.
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