http://www.canada.com/ottawacitizen/news/story.html?id=7dca07ac-ac50-...

OTTAWA- Cumbaa and four fishing buddies are back from the Northwest
Territories, toting 400 kilograms of ancient fish, preserved for the
really long term. They're fossilized.

And the specimens so far show some features not often found in fish
from 400 million years ago: jaws, for instance. And modern-style fins.
And a couple of armour-plated skulls that bend in the middle.

As a paleontologist at the Canadian Museum of Nature, he and a team
from the museum and the University of Kansas have been digging for
ancient fish where the modern Anderson River has cut through old rock,
350 kilometres east of Inuvik. This area was on, or near the equator
all those millions of years ago.

"It was an equatorial, warm, shallow sea," Mr. Cumbaa said, and a site
where he discovered preliminary scraps 11 years ago.

He says there's evidence it was a "hotbed for evolution."

This means, cutting through a lot of Greek terminology of placoderms
and melano-gnathuses and the like, that Canada's northern rocks hold
ancient tropical fish that don't fit the ancient pattern.

Most fish from the Devonian period didn't have jaws. "They looked like
little dustbusters, hoovering up the bottom sediments," Mr. Cumbaa
says. "They're pretty uninteresting looking things."

The Anderson River fish did have jaws, all of them. These include
fossils of tiny sharks, just two or three centimetres long; and a
species that may be the earliest ray-finned fish on Earth. Ray-finned
fish are the type we typically see today: Their fins are very thin and
stretched on a frame of spiky bones, unlike the lobe-finned variety
(with fleshy fins) that has nearly died out over millions of years.
Also, they have pieces of a fish with lungs.

And finally, of course, the top fish, a predator with an extremely
thick, heavy skull, belonging to a new genus (group of related
species) of fish in the bigger group called arthrodires, or armoured
fish.

Devonian fish were small by today's standards, but the first two
specimens of this predator are each a sturdy 1.5 metres long, making
them the biggest hunters in the sea back then. They also had a funny
skull with a gap midway, allowing the front part to shift position on
its own.

Overall, says Mr. Cumbaa, "it's a diverse group of fishes,
representative of some of the earliest lungfishes and certainly the
earliest ray-finned fish. And to have this kind of assemblage all at
once - more highly evolved, you might say - makes me wonder if this
wasn't some kind of hot spot for the evolution of these jawed
vertebrates."

The innovation of an armoured skull didn't last forever. Armoured fish
are extinct today.

Why?

"Other organisms just had a better game plan, I guess," the
paleontologist said. "You know, more flexible in habitat."

Now the job is to clean the fish. In this case, it means removing
rock, not innards.

"We've got to peel that rock off, sort of grain by grain," the
scientist said. It will take many months.

--
Bob.