419-million-year-old armoured fish fossil resolves 'missing link' in evolution, scientists say

An artist's impression of an Entelognathus - an armoured fish. Image obtained on September 24, 2013. AFP: Brian Choo/Chinese Academy of Sciences

AM By Tom Nightingale

A team of scientists, including an Australian, have found a fossil of a 419-million-year-old ancient armoured fish, in what is being hailed as the most significant paleontological discovery in decades. 

Palaeontologists say the fossilised fish, which was found in the suburbs of a city in south-west China, is probably the earliest creature with a recognisable jaw.

Hundreds of millions of years ago, fish known as Placoderms had armoured plates and dominated the oceans.

For years, the world's top evolutionary scientists thought Placoderms died out and then somehow modern fish evolved.

Flinders University's Professor John Long say the discovery resolves a major missing link in evolution.

"The unknown question was where did modern fish fauna come from, who was their ancestor?" Professor Long said.

"This ancient fish called Entelognathus is the missing link because it shows that the extinct armoured Placoderms fishes, which dominated the seas, rivers and lakes of the world for 70 million years, actually were the ancestors to all the living fish on the planet today."

At the time of its existence, the fish lived in a warm tropical sea when China was a separate landmass to Asia.

Discovery calls for further research

Professor Long says the fossil dates to about 50 million years before fish became amphibious.
"This is a huge discovery for science, not just palaeontology," he said.

"This fish fills a gap between an extinct class of animals and the entire living fish fauna on the planet, which is 30,000 species.

"It's a huge discovery that fills a massive gap in our knowledge of the evolution of the first backboned animals."

The Chinese Academy of Science's Professor Zhu, who led the study, says the fossil's jaw looks a lot like those of modern fish.

She says this shows the Placoderm to be the ancestors of modern fish.

"It has a jaw similar to the modern fish, so we can see intermediary between Placoderms and modern fish or modern vertebrae," Professor Zhu said.

As well as in China, significant ancient fossils have also been found in Australia.

Professor Long says the Amadeus Basin, east of Alice Springs, is another place where scientists could unlock the mysteries of evolution.

"We think that the biggest gap in the whole of early vertebrate evolution, down the base of the whole tree, is gap between the jawless fishes and the first jawed fishes like these armoured Placoderms," he said.

"There hasn't been any transition intermediate fossil formed in that space yet found, but the oldest fossil fishes with bone occur right here in central Australia.

"I think a lot more searching needs to be done and we could find the answers to some of these really big questions right here in our own country."

The mainly Chinese research team includes an Australian former PhD student of Professor Long.

The study is published in the journal Nature today.

Guessing at Nessie

Artist's reconstruction of the plesiosaur. Illustration Orlando Grillo and Maurilio S. Oliviera

Those who are convinced that something larger than the average fish really does live in Loch Ness have come up with an abundance of theories. One of the most popular ideas is that Nessie is actually a prehistoric, aquatic animal called a plesiosaur, a creature that closely matches the Spicers' description of the beast that crossed the road. The main problem with this idea is that the plesiosaur has been extinct for 65 million years.

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Few prehistoric creatures come as close to matching the Spicer couple's physical description of Nessie as the long-necked plesiosaurs. These bulbous-bodied, flippered marine reptiles popped into the fossil record 220 to 175 million years ago, and they continued to flourish and adapt until about 65 million years ago when, it is assumed, they went extinct. Plesiosaurs came in a variety of species over the millennia, some with very long and slender necks, and others, called pliosaurs, with shorter necks and long heads. They ranged in size from about eight to just under 50 feet long!

It may have been the resemblance of the long-necked species to the famous "Surgeon's Photograph" that led people to suggest that Loch Ness contains a relict plesiosaur. But studies of fossil specimens, some discovered as recently as 2002, have caused zoologists to speculate that it might have been very difficult for a plesiosaur to hold its narrow neck out of the water while swimming. The neck would tend to bob forward due to gravity.

On the Web site, "The Plesiosaur Site," scholar and plesiosaur expert Richard Forrest says, "The long neck, being mainly bone and muscle will be denser than water, and denser than the main body which contains lungs, and a digestive system generating gasses. This would tend to make the head sink, and lead to a great waste of energy in trying to keep it up." The long neck would work admirably well, however, for foraging the sea bottom or surveying the surface from below.

Given its long rule of the prehistoric seas, the plesiosaur was a very successful animal in its time. Might it have been even more successful than scientists think, with a few individuals still cavorting along the bottom of Loch Ness?

Forrest, along with most other experts, thinks not. Plesiosaurs needed to breathe air, and sightings would be much more common in the Loch than they are since the animals would need to surface regularly. He also notes that Loch Ness is too cold for a marine reptile, that the lake is only 10,000 years old and the plesiosaurs went extinct 65 million years ago, and that its body shape does not match sightings that describe undulating humps in the water. True believers answer that the plesiosaur could have adapted over time to changing water temperature, that it could have entered the Loch through underground passageways, and that the humps might have been formed by its back and tail.

Loch Ness is not the only place where plesiosaurs are thought to roam. They have been claimed for many other water habitats around the world wherever monsters have been sighted. But until a live or well-preserved dead plesiosaur presents itself for human inspection, most scientific investigators will continue to consider it strictly a predator of the past.

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Other researchers have suggested Nessie could actually be a long-snouted Baltic sturgeon, an out-of-place porpoise, an elongated seal, a string of otters swimming in a straight line (creating the appearance of a series of humps), a type of whale, shadows, or even a floating log spewed from the depths by a narrow, standing wave of water called a seiche. Some think that although the lake has been shown to be too small to support the breeding population that would be required to keep a monster family thriving (estimated at between 30-50 individuals), undiscovered undersea caverns and connections to the North Sea could provide a habitat for a family of large marine creatures. That also would help explain how a 2003 sonar sweep using satellite navigation and conducted of the entire lake by the BBC could fail to turn up any sign of Nessie. She might simply have been lounging in an adjacent cavern or cruising at sea.

Another line of thought states Nessie doesn't need a breeding population because she is not a physical being. Scotland has a tradition of a mythic creature called a kelpie, or water horse. Kelpies were said to lurk alongside lake or river trails, appearing as a beautiful horse that stood saddled and ready to ride. But the instant a hapless traveler mounted the alluring creature, it would dash into the water, revert to its true form, and dine on its rider.

Whatever Nessie is, the towns around Loch Ness know a good thing when it swims by. The village of Drumnadrochit advertises the "Original Loch Ness Visitor's Center," which offers boat cruises and a variety of Nessie tourist paraphernalia. The rest of the local economy also benefits from the hordes of monster-seekers who come hoping for a glimpse of the lake's mascot.

Chances that a good photo may be taken of Nessie have increased in modern times with more and more people trying to capture a "money" shot of the monster. On June 9, 2007, organizers of a music event called "Rock Ness" handed out 50,000 cameras to attendees in the hope that one might catch an image of the lake serpent. Just a week before that, a bounty of $1 million British pounds was offered for Nessie's capture. If Nessie ever is discovered to be a real creature, perhaps the find will not be made by scientists but by one of the millions of visitors who have made the Loch a must-see destination.