Transitional Species

[August]

Right, but how is this different from other tetrapods?

Tiktaalik was not a tetrapod. It has fins and fishlike jaws. It probably did not posess vertebrae but a primitive notochord like structure. Because of this it could not have lived primarily on land.

Of course, I read that before, I'm an idiot. I gues what I was trying to ask was what are the unique characteristics in this specimen that makes it an ancestor to tetrapods?

[BGoodForGoodSake]

Right, but how is this different from other tetrapods?

Tiktaalik was not a tetrapod. It has fins and fishlike jaws. It probably did not posess vertebrae but a primitive notochord like structure. Because of this it could not have lived primarily on land.

Of course, I read that before, I'm an idiot. I gues what I was trying to ask was what are the unique characteristics in this specimen that makes it an ancestor to tetrapods?

Well to be more specific it is not known whether this form was a direct ancestor to tetrapods or a related sister group.

The features are as follows.
The ability to move the head independant of the body due to a neck. (fish do not possess necks as outlined in a previous post.)
Shoulders and arm bones making up the elbow.
As well as a primitive wrist??
A flattened skull.
Wide rib cage with overlapping ribs.
Eyes on the top of the head.
Possibly had lungs??

[August]

Right, but how is this different from other tetrapods?

Tiktaalik was not a tetrapod. It has fins and fishlike jaws. It probably did not posess vertebrae but a primitive notochord like structure. Because of this it could not have lived primarily on land.

Of course, I read that before, I'm an idiot. I gues what I was trying to ask was what are the unique characteristics in this specimen that makes it an ancestor to tetrapods?

Well to be more specific it is not known whether this form was a direct ancestor to tetrapods or a related sister group.

The features are as follows.
The ability to move the head independant of the body due to a neck. (fish do not possess necks as outlined in a previous post.)
Shoulders and arm bones making up the elbow.
As well as a primitive wrist??
A flattened skull.
Wide rib cage with overlapping ribs.
Eyes on the top of the head.
Possibly had lungs??

Thanks. As always, I will ask how we know that this fits into a specific lineage, as opposed to being a seperate species? The question seems a bit redundant since you already said we don't know what lineage this is supposed to fit into.

[BGoodForGoodSake]

Thanks. As always, I will ask how we know that this fits into a specific lineage, as opposed to being a seperate species? The question seems a bit redundant since you already said we don't know what lineage this is supposed to fit into.

I not quite sure what your distinction between lineage and species is. As a lineage would be made up of distinct sequence of species.

The presence of features found in later tetrapods, in this fish would suggest that either this group or a related group gave rise to tetrapods.

[August]

Thanks. As always, I will ask how we know that this fits into a specific lineage, as opposed to being a seperate species? The question seems a bit redundant since you already said we don't know what lineage this is supposed to fit into.

I not quite sure what your distinction between lineage and species is. As a lineage would be made up of distinct sequence of species.

The presence of features found in later tetrapods, in this fish would suggest that either this group or a related group gave rise to tetrapods.

I meant that we can see this specimen as part of a series of species, or we can see it as a species that existed at a specific point in time, but was not an ancestor to anything.

Did we ever discuss common descent anywhere? That is the underlying premise of the conclusion you state above.

[BGoodForGoodSake]

I meant that we can see this specimen as part of a series of species, or we can see it as a species that existed at a specific point in time, but was not an ancestor to anything.

How would you classify a fish which possesses a neck, shoulder and arm bones?

Did we ever discuss common descent anywhere? That is the underlying premise of the conclusion you state above.

The term transitional species implies common descent. The conclusion is not mine per say, but that of the article.

[August]

I meant that we can see this specimen as part of a series of species, or we can see it as a species that existed at a specific point in time, but was not an ancestor to anything.

How would you classify a fish which possesses a neck, shoulder and arm bones?

It's still a fish. I also do not think that this specimen has "arm bones", or "shoulders", it was the extrapolation that the structures could develop into those.

Did we ever discuss common descent anywhere? That is the underlying premise of the conclusion you state above.

The term transitional species implies common descent. The conclusion is not mine per say, but that of the article.

I understand it is not your conclusion. On what basis is common descent postulated in this case?

[BGoodForGoodSake]

I understand it is not your conclusion. On what basis is common descent postulated in this case?

It's not a case by case issue.
A theory is an all encompassing idea with support and applications in multiple fields.

[August]

I understand it is not your conclusion. On what basis is common descent postulated in this case?

It's not a case by case issue.
A theory is an all encompassing idea with support and applications in multiple fields.

Ah, so it is a-priori accepted, and any new discovery is made to fit the theory?

[BGoodForGoodSake]

I understand it is not your conclusion. On what basis is common descent postulated in this case?

It's not a case by case issue.
A theory is an all encompassing idea with support and applications in multiple fields.

Ah, so it is a-priori accepted, and any new discovery is made to fit the theory?

Yes the entire fossil history is arranged to fit the theory, that is what creates the missing links. Any new evidence will be weighed againt existing theories, however fossil evidence in itself is insuffucient to support a theory.

Before this discovery was made a specific time span and location was selected based on subsets of the theory to locate the missing link. In a sence the discovery of a transitional form reafirms current theories on tetrapod evolution.
Lobefin fish --> Tiktaalik --> Early Tetrapods

380 Million Years ago
Lobefin fish lack shoulders and a neck.

365 million years ago
Early Tetrapods show eight digits in the forelimbs and seven in the back, and have flattened skulls with eyes on top.

375 million years ago
Tiktaalik has a shoulder and neck, with fins and a flattened skull with eyes on the top. And it occurs in the time period between the two existing finds.

The new findings form and date fits in with the current theories regarding the ascent of tetrapods from fish.

Genetic analysis also indicates a duplication of chromosomes occurred during roughly the same period.

[August]

I understand it is not your conclusion. On what basis is common descent postulated in this case?

It's not a case by case issue.
A theory is an all encompassing idea with support and applications in multiple fields.

Ah, so it is a-priori accepted, and any new discovery is made to fit the theory?

Yes the entire fossil history is arranged to fit the theory, that is what creates the missing links.

Before this discovery was made a specific time span and location was selected based on the subsets of the theory to locate the missing link.

The new finding fits in with the current theories regarding the ascent of tetrapods from fish.

Hang on, isn't that a tad circular? If common descent was induced from the homology of features, then you cannot state that this confirms the theory, because it has features that are common to ancestors.

[BGoodForGoodSake]

Hang on, isn't that a tad circular? If common descent was induced from the homology of features, then you cannot state that this confirms the theory, because it has features that are common to ancestors.

Common descent was deduced from homology of features in living specimens. Not from the homology of yet to exist fossil finds.
That is all discussed here.

There is a subset of the theory of Evolution regarding the origin of tetrapods.

Before the find, lobe finned fish were identified as the most likely candidate for tetrapod ancestor. This was based on certain anatomical features. However there still remained a large gap regarding the development of limbs, vertebrae, shoulder and elbow joints, and the ear.

The recent finding shows that perhaps the limbs formed before the digits, and may give us a clue as to how the ear developed.

It is not circular reasoning to apply a theory to a new discovery.

For example A therefore B therefore A is circular reasoning.
I exist therefore I know I exist.
Because I know I exist I must exist.

What we are doing is applying an idea.
I know I exist therefore I exist.
You also know that you exist therefore you must exist as well.

[August]

Hey Bgood, I will spin this off into a new thread. I have seen a different account for the origin of homology and common descent, based on cladistics.

[BGoodForGoodSake]

Hey Bgood, I will spin this off into a new thread. I have seen a different account for the origin of homology and common descent, based on cladistics.

Go for it.
=)

[tyler_demerhcant]

One thing I don't understand is why all fossils are thought to be fully developed?

There are several creatures that transfrom within their lifespan, frog's being the most obvious.

How many fossils of tiktalik were found?

What dating mechanism was used to aquire the age?

How was the fossil fossilized?

If you believe in a young earth as I do, this fossil proves unimportant, but I myself find it interesting.

However, no ammount of speculation can make up for the lack of transitional fossils. Two or three is it? and a large faction of creation scientists have logical reasoning to believe that the fossils were not "missing links" at all.

Over speculated indeed my the press. It is so unfortunate that so many people are subject to the teachings of evolution without a view point from the other side. The same goes for christian schools, they just don't teach the evolutionary side. If people aren't prepared for a debate, they often lose hope all to soon and are easily persuaded.

This fossil in no way changes the tide in the evolution vrs. creation debate.