'Fishapod' reveals origins of head and neck structures of first land animals

Oct 15, 2008
A new study of Tiktaalik roseae (middle), a 375-million-year-old transitional fossil, highlights an intermediate step between the condition in fish like Eusthenopteron (bottom) and that in early limbed forms like Acanthostega (top). The new data are described in a paper by Jason Downs, Ted Daeschler and Neil Shubin in the Oct. 16 edition of Nature. Credit: Kalliopi Monoyios

(PhysOrg.com) -- Newly exposed parts of Tiktaalik roseae--the intermediate fossil between fish and the first animals to walk out of water onto land 375 million years ago--are revealing how this major evolutionary event happened. A new study, published this week in Nature, provides a detailed look at the internal head skeleton of Tiktaalik roseae and reveals a key intermediate step in the transformation of the skull that accompanied the shift to life on land by our distant ancestors.

A predator, up to nine feet long, with sharp teeth, a crocodile-like head and a flattened body, Tiktaalik's anatomy and way of life straddle the divide between fish and land-living animals. First described in 2006, and quickly dubbed the "fishapod," it had fish-like features such as a primitive jaw, fins and scales, as well as a skull, neck, ribs and parts of the limbs that are similar to tetrapods, four-legged animals.

The initial 2006 report did not describe the internal anatomy of the head, because those parts of the fossil were buried in rock. In the October 16, 2008, issue of Nature, the researchers describe this region and show how Tiktaalik was gaining structures that could allow it to support itself on solid ground and breathe air.

"We used to think of this transition of the neck and skull as a rapid event," said study author Neil Shubin, PhD, of the University of Chicago and Field Museum and co leader of the project, "largely because we lacked information about the intermediate animals. Tiktaalik neatly fills this morphological gap. It lets us see many of the individual steps and resolve the relative timing of this complex transition."

"The braincase, palate, and gill arch skeleton of Tiktaalik have been revealed in great detail by recent fossil preparation of several specimens," said Jason Downs, PhD, a postdoctoral research fellow at the Academy of Natural Sciences and lead author on the new study. "By revealing new details on the pattern of change in this part of the skeleton, we see that cranial features once associated with land-living animals were first adaptations for life in shallow water."

"The new study reminds us that the gradual transition from aquatic to terrestrial lifestyles required much more than the evolution of limbs," said Ted Daeschler, PhD, of the Academy of Natural Sciences and co-leader of the team that discovered Tiktaalik. "Our work demonstrates that, across this transition, the head of these animals was becoming more solidly constructed and, at the same time, more mobile with respect to the body." These changes are intimately associated with the change in environment.

Fish in deep water move and feed in three-dimensional space and can easily orient their body in the direction of their prey. A neck, seen for the first time in the fossil record in Tiktaalik, is advantageous in settings where the body is relatively fixed, as is the case in shallow water and on land where the body is supported by appendages planted against a substrate.

Another important component of this transition was the gradual reduction of the hyomandibula, a bony element that, in fish, coordinates the cranial motions associated with underwater feeding and respiration. In the transition to life on land, the hyomandibula loses these functions and the bone becomes available for an eventual role in hearing.

In humans, as in other mammals, the hyomandibula, or stapes, is one of the tiny bones in the middle ear. "The bony part of Tiktaalik's hyomandibula is greatly reduced from the primitive condition," said Downs, "and this could indicate that these animals, in shallow water settings, were already beginning to rely less on gill respiration."

The discoveries were made possible by laboratory preparators Fred Mullison and Bob Masek, who prepared the underside of the skull of specimens collected in 2004. This painstaking process took several years. This work showed the underside of the skull and gill bones "beautifully preserved," said Shubin, "to a degree unlike any creature of its kind at this transition."

Having multiple Tiktaalik specimens enabled the researchers to prepare the fossils in ways that showed the bones of the head in "exceptional detail," Downs said.

The team discovered Tiktaalik roseae on Ellesmere Island, in the Nunavut Territory of Canada, 600 miles north of the Arctic Circle. Though this region of Nunavut is now a harsh Arctic ecosystem, at the time that Tiktaalik lived, the area was much further south and was a subtropical floodplain ecosystem.

The formal scientific name for the new species, "Tiktaalik" (tic-TAH-lick), was derived by the Elders Council of Nunavut, the Inuit Qaujimajatuqangit. The Inuktikuk word means "a large, shallow-water fish." The paleontology team works in Nunavut with authorization from the Department of Culture, Language, Elders and Youth. All fossils are the property of the people of Nunavut and will be returned to Canada after they are studied.

Provided by University of Chicago

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ZeroDelta
3 / 5 (2) Oct 15, 2008
There are some amizing fossils that
will never be found and it just kills me !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
AdseculaScientiae
3 / 5 (2) Oct 16, 2008
Intermediate fossils?!

My church tells me that is a myth!

Lies, lies, All these lies..

;)

Nice article.
mabarker
1 / 5 (2) Oct 20, 2008
Adsecula - your sarcasm aside, if you do not believe creation scientists just remember we have all heard this "missing link" story before. I.e. with coelacanths, a fish once known ONLY from the fossil record. The lobed fins on the fossil specimens fueled evolutionary claims that it walked on the ocean floor and 'evolved into' a land-walker.

Can darwinists show us how random genetic mutations can account for the genetic information to create working, useful anatomical features? I didn't think so.

Consider, for example, the variation in the head shapes of the many types of fish and aquatic creatures. To describe Tiktaaliks head as part of a trend is 100 percent darwinian interpretation. Anything more is sheer speculation based on the observers underlying presuppositions. Yes, darwinists presuppose people came from rock.

The interactions between other parts of Tiktaaliks head skeleton are also described as changing, something clearly impossible with fossilized skeletons. The change is not in the fossil record; it is occurring in the minds of those who already believe in macroevolution. And even if there is a clear evolutionary explanation for why a particular structure would be advantageous, that does not mean it evolved. Tiktaalik neatly fills this morphological gap, and helps to resolve the timing of this complex transition, said 1 darwinist. But it's only because he presupposes that morphological similarities indicate where a creature belongs in an evolutionary lineage. This is the same logic that says a middle-sized horse must be the intermediary between a small horse and a large horse, when in fact we see all three alive today. But when a creature is only known from the fossil record, evolutionists are free to speculate about its role in the evolutionary process.



geronimo454
not rated yet Oct 21, 2008

Gotta love those creationists...

>>Can darwinists show us how random genetic mutations can account for the genetic information to create working, useful anatomical features? I didn't think so. >Yes, darwinists presuppose people came from rock. >The interactions between other parts of Tiktaaliks head skeleton are also described as changing, something clearly impossible with fossilized skeletons. The change is not in the fossil record; it is occurring in the minds of those who already believe in macroevolution> This is the same logic that says a middle-sized horse must be the intermediary between a small horse and a large horse, when in fact we see all three alive today. But when a creature is only known from the fossil record, evolutionists are free to speculate about its role in the evolutionary process.
geronimo454
5 / 5 (1) Oct 21, 2008

Gotta love those creationists...

--Can darwinists show us how random genetic mutations can account for the genetic information to create working, useful anatomical features? I didn't think so. --

Your belief does not make it so or not so, my irrational friend. There are reams of material on how mutation leads to accumulated change over time. You don't need to believe in evolution. Evolution believes in you.

--Yes, darwinists presuppose people came from rock. --

An empty and bizarre quote that creationists seem to find meaningful. In fact, the theory is that life began in a primordial soup of amino acids. Amino acids are organic compounds not rocks. Wild guess here but can we suppose you are not an Organic Chem major?
Creationist Organic Chem student: Why did I fail my Organic Chem exam? Aren't amoebas made out of granite?

--The interactions between other parts of Tiktaaliks head skeleton are also described as changing, something clearly impossible with fossilized skeletons. The change is not in the fossil record; it is occurring in the minds of those who already believe in macroevolution--

Right. Fossils don't change... they are after all fossils. Good we can agree on something. Wild guess here, but can we suppose you are not a Homicide Detective?
Creationist Homicide Detective: You see your honor, just because we found a bullet in the wall behind the victim that matches the gun doesn't necessarily mean that a demon didn't just smite the victim with hellfire and make it LOOK like a gunshot wound. Now lets go find an old lady to burn as a witch and wrap up this case!

-- This is the same logic that says a middle-sized horse must be the intermediary between a small horse and a large horse, when in fact we see all three alive today. But when a creature is only known from the fossil record, evolutionists are free to speculate about its role in the evolutionary process. --

Science is about discovering these relationships. And you offer what exactly? the theory that these animals magically popped into existence fully formed in a magical land of lollipops and serpents?

If you have an alternative or conflicting hypothesis that involves reproducible experiments you are welcome in science. I suppose we may need to specify that automatic knowledge via revelation, burning bushes, reading chicken entrails, speaking tongues, casting bones, sacrificing animals (or sons, or virgins), or oblique parables from texts cobbled together by barely literate savages that condone slavery are not classified as actual scientific proof.

Good for you for actually reading a hard science site like Phyorg.com. Over time it might actually help you think for yourself. Keep up the good work, but leave the heavy intellectual lifting for those better suited for it.

Redeem you mind from the hockshops of authority. Faith in the supernatural begins as faith in the superiority of others.




AdseculaScientiae
not rated yet Nov 02, 2008
@geronimo

What about the shape of a banana that -CLEARLY- fits into our hands perfectly?

You can't refute thát piece of evidence for the existence of our personal God.

Take that, you heathen spawn of Hell!


Seriously;

Sorry for not responding to your post mabarker, but I think you should get some education before you start giving 'arguments' why evolution is false. First; evolution is not only driven by 'random pointmutations'. We are just beginning to understand how evolution works in detail and in big lines. There are several examples within our time of big anatomical changes (while most of them are disadvantuous; there is a slight chance of a advantuous change). Like geronimo already explained, darwinists (what is a darwinist anyway?) do nót think people came from rock.. In fact, your little faith describes God made humans out of mud. Fossils can, like you say, not change at all. We have found many fossils, intermediates (not to mention that every species is indeed a intermediate) too, but you must understand they are just a small, really small percentage of every species that ever existed. Even with this relatively small amount we can see great associations with eachother.

Scientists mostly don't have an special agenda, I can not imagine anyone who wants the theory of evolution to be true if all the evidence would point in favor of creation. Of course we deeply want to be special and the favorite species of the Celestial Granddaddy of All.

But truth is.. All the evidence (and that is A LOT) point toward evolution, not creation.

The sooner you become intellectually honest with yourself, the sooner you will acknowledge this this.