Tetrapods are older than we thought!

| 96 Comments

Some stunning fossil trackways have been discovered in Poland. The remarkable thing about them is that they’re very old, about 395 million years old, and they are clearly the tracks of tetrapods. Just to put that in perspective, Tiktaalik, probably the most famous specimen illustrating an early stage of the transition to land, is younger at 375 million years, but is more primitive in having less developed, more fin-like limbs. So what we’ve got is a set of footprints that tell us the actual age of the transition by vertebrates from water to land had to be much, much earlier than was expected, by tens of millions of years.

Here are the trackways. Note that what they show is distinct footprints from both the front and hind limbs, not drag marks, and all that that implies: these creatures had jointed limbs with knees and elbows and lifted them and swung them forward to plant in the mud. They were real walkers.

trackway1.jpeg

trackway2.jpeg

Trackways. a, Muz. PGI 1728.II.16. (Geological Museum of the Polish Geological Institute). Trackway showing manus and pes prints in diagonal stride pattern, presumed direction of travel from bottom to top. A larger print (vertical hatching) may represent a swimming animal moving from top to bottom. b, On the left is a generic Devonian tetrapod based on Ichthyostega and Acanthostega fitted to the trackway. On the right, Tiktaalik (with tail reconstructed from Panderichthys) is drawn to the same shoulder-hip length. Positions of pectoral fins show approximate maximum ‘stride length’. c, Muz. PGI 1728.II.15. Trackway showing alternating diagonal and parallel stride patterns. In a and c, photographs are on the left, interpretative drawings are on the right. Thin lines linking prints indicate stride pattern. Dotted outlines indicate indistinct margins and wavy lines show the edge of the displacement rim. Scale bars, 10 cm.

They were also big, approximately 2 meters long. What you see here is a detailed scan of one of the footprints of this beast; no fossils of the animal itself have been found, so it’s being compared to the feet of Ichthyostega and Acanthostega, two later tetrapods. There are definite similarities, with the biggest obvious difference being how much larger the newly-discovered animal is. Per Ahlberg makes an appearance in a video to talk about the size and significance of the mystery tetrapod.

foot.jpeg

Foot morphologies. a, Laser surface scan of Muz. PGI 1728.II.1, left pes. b, Complete articulated left hind limb skeleton of Ichthyostega, MGUH f.n. 1349, with reconstructed soft tissue outline. c, Left hind limb of Acanthostega, reconstructed soft tissue outline based on skeletal reconstruction in ref. 8. We note the large size of the print compared to the limbs of Ichthyostega and Acanthostega, and that the print appears to represent not just the foot but the whole limb as far as the knee. d, digit; fe, femur; ti, tibia; fi, fibula; fib, fibulare. Scale bars, 10 mm.

What’s it all mean? Well, there’s the obvious implication that if you want to find earlier examples of the tetrapod transition, you should look in rocks that are about 400 million years old or older. However, it’s a little more complicated than that, because the mix of existing fossils tells us that there were viable, long-lasting niches for a diversity of fish, fishapods, and tetrapods that temporally coexisted for a long period of time; the evolution of these animals was not about a constant linear churn, replacing the old model with the new model every year. Comparing them to cars, it’s like there was a prolonged window of time in which horse-drawn buggies, Stanley Steamers, Model Ts, Studebakers, Ford Mustangs, and the Honda Civic were all being manufactured simultaneously and were all competitive with each other in specific markets…and that window lasted for 50 million years. Paleontologists are simply sampling bits and pieces of the model line-up and trying to sort out the relationships and timing of their origin.

The other phenomenon here is a demonstration of the spottiness of the fossil record. The Polish animal has left us no direct fossil remains; the rocks where its footprints were found formed in an ancient tide flat or lagoon, which is not a good location for the preservation of bones. This suggests that tetrapods may have first evolved in these kinds of marine environments, and only later expanded their ranges to live in the vegetated margins of rivers, where the flow of sediments is much more conducive to burial and preservation of animal remains. That complicates the story, too; not only do we have diverse stages of the tetrapod transition happily living together in time, but there may be a bit of selective fossilization going on, that only preserves some of the more derived forms living in taphonomically favorable environments.


Niedzwiedzki G, Szrek P, Narkiewicz K, Narkiewicz M, Ahlberg PE (2010) Tetrapod trackways from the early Middle Devonian period of Poland. Nature 463(7277): 43-48.

96 Comments

Wow. Wow, wow, wow.

Given the extinction record I can’t help wondering if this was a dead end or actually led to a tetrapod line.

I like the car analogy. Some started early and the line is unbroken, some started late and disappeared.

Doesn’t this put the emergence of land tetrapods surprisingly close to the emergence of boney fish?

The sedimentary structure would have been destroyed within weeks or months due to bioturbation, before hardening to rock. The footprints were preserved because they were rapidly buried in the global flood. This is similar to the Pterodactyl landing tracks recently found in France, footprints found in New Zealand, even a footprint in the Grand Canyon.

Why did it have to be a global flood? How come it could not have been a local flood? The pterodactyl landing tracks are from the Mesozoic. How could such flying reptiles have landed successfully in such a tempestuous storm?

Get stuffed, creationist twit. Find some other site to babble on, because I’m putting the hammer down on you here.

harold said:

Doesn’t this put the emergence of land tetrapods surprisingly close to the emergence of boney fish?

I thought the ancestors of what we humans recognize as “bony fish” today diverged from the sarcopterygians during the early Silurian.

Stanton -

That appears to be correct (*I am not even close to being either a paleontologist or an ichthyologist*).

However, I probably should have said “boney fish advanced enough to be temporally close ancestors to tetrapods with fully developed walking and capacity for respiration on land”.

Of course, I’m talking about tens of millions of years as “close” here.

However, it’s a little more complicated than that, because the mix of existing fossils tells us that there were viable, long-lasting niches for a diversity of fish, fishapods, and tetrapods that temporally coexisted for a long period of time; the evolution of these animals was not about a constant linear churn, replacing the old model with the new model every year. Comparing them to cars, it’s like there was a prolonged window of time in which horse-drawn buggies, Stanley Steamers, Model Ts, Studebakers, Ford Mustangs, and the Honda Civic were all being manufactured simultaneously and were all competitive with each other in specific markets…and that window lasted for 50 million years. Paleontologists are simply sampling bits and pieces of the model line-up and trying to sort out the relationships and timing of their origin.

Of course, that’s very similar to what we see in the modern biosphere - with apologies for using some “garbage can” terms, we see fish, amphibians, reptiles, and mammals temporally co-existing.

henry said:

The footprints were preserved because they were rapidly buried in the global flood…

The global flood happened 375 million years ago?

This is similar to the Pterodactyl landing tracks recently found in France, footprints found in New Zealand, even a footprint in the Grand Canyon.

And yet none of these animals made it onto Noah’s big boat?

How was that, Henry? Did God not command Noah to take 2 of every animal?

Did Noah just disobey? (that could go badly, look at what happened to Onan)

Did Noah manage go gather two of every know agricultural pest but somehow overlook the tetrapods, pterodactyls and other big lizards that were apparently out and about leaving footprints around weeks before the flood?

No PZ, don’t do it! I want to hear more about how the turbidity/viscosity of mud drying in air is so much higher than the turbidity of mud in a huge flood.

More rope, more rope!

Michael Buratovich said:

Why did it have to be a global flood? How come it could not have been a local flood? The pterodactyl landing tracks are from the Mesozoic. How could such flying reptiles have landed successfully in such a tempestuous storm?

A local flood could not have accomplished what only a global flood could do. This article from ICR describes how a recent study demonstrates that the current processes prohibit footprints from being fossils.

Sedimentary Structure Shows a Young Earth Share this Article by John D. Morris, Ph.D. *

1. Gingras, M. K. et al. 2008. How fast do marine invertebrates burrow? Palaeogeography, Palaeoclimatology, Palaeoecology. 270 (3-4): 280-286.

Cite this article: Morris, J. 2009. Sedimentary Structure Shows a Young Earth. Acts & Facts. 38 (7): 15.

Henry, you are a goddamned lying moron.

PZ Myers said:

Get stuffed, creationist twit. Find some other site to babble on, because I’m putting the hammer down on you here.

You are obviously a brilliant man. Too bad your God given gifts aren’t used for His glory, rather than for evolution or Darwin.

henry, please take Prof. Myers’ advice.

The only person you succeed in impressing with your copy and pasted quotemines and inane lies from Answers in Genesis is yourself.

Too bad your God given gifts aren’t used for His glory

Why is your insecure god so in need of glorification? And anyway, he’s supposedly omnipotent, so why doesn’t he just make his own glory, if he craves it so?

Three feet of rope awarded to Henry for his three posts. Two bonus feet awarded: one for citing ICR, another for telling us what God thinks of our efforts. (Remember Henry, you’re suppossed to be pretending that there’s nothing religious about ID.)

henry said: You are obviously a brilliant man. Too bad your God given gifts aren’t used for His glory, rather than for evolution or Darwin.

Isn’t a deity who craves “glory” from a being on a minor rock circling a mediocre star in an obscure corner of a slightly-above-average galaxy a bit rancid, when compared to the deity who created the nifty stuff we see in the starry heavens, and who has glory to spare in his own right?

henry Wrote:

A local flood could not have accomplished what only a global flood could do.

Have you discussed that with Discovery Institute folk? They seem to think (and at least one defnitely thinks) that there was no global flood. Also, since you referenced ICR, does that mean that you disagree with most DI folk and all RTB folk on when all sorts of events occurred. So have you chalenged them?

Henry, I recommend you take a look at Talk Origins, particularly http://www.talkorigins.org/faqs/icr[…]artelt4.html, which outlines some of the basic flaws in your arguments.

Shebardigan said:

Isn’t a deity who craves “glory” from a being on a minor rock circling a mediocre star in an obscure corner of a slightly-above-average galaxy a bit rancid, when compared to the deity who created the nifty stuff we see in the starry heavens, and who has glory to spare in his own right?

How about a deity that craves worship from idiots who despise the universe the deity created.

This sounds like a deity that wallows in the worst crap and mistakes it created.

Ben W said:

Henry, I recommend you take a look at Talk Origins, particularly http://www.talkorigins.org/faqs/icr[…]artelt4.html, which outlines some of the basic flaws in your arguments.

I hate to tell you this, Ben, but, people have showed henry that particular link, repeatedly.

henry apparently glorifies God by flaunting his willful stupidity and gross dishonesty.

I hate to tell you this, Ben, but, people have showed henry that particular link, repeatedly.

henry apparently glorifies God by flaunting his willful stupidity and gross dishonesty.

So he really is a goddamned lying moron? Aww, shucks.

eric said:

Three feet of rope awarded to Henry for his three posts. Two bonus feet awarded: one for citing ICR, another for telling us what God thinks of our efforts. (Remember Henry, you’re suppossed to be pretending that there’s nothing religious about ID.)

Point of clarification, henry is a hard-core YEC (even cites the ICR) and would have very little in common with the ID proponents, except for Paul Nelson, maybe.

This may be pure babble, but follow me here.

The date of first tetrapods would probably have to be pushed back even further.

I would suspect that this is a predator. 1) There were only simple land plants (at best) during this time period. A two meter animal like this would have a hard time surviving on hornworts. 2) It probably couldn’t swim well enough to catch larger fish (because of those large, stupid limbs sticking out from the side). 3) So it was probably a predator of other (smaller) tetrapods that couldn’t move as quickly because of size. (At this point, pretty much the only way to go faster was to be bigger, there wasn’t enough variation in limbs structure to produce sprinters and runners, etc) 4) So this ate tetrapods smaller than itself, so there must have been a pretty large population of those guys running around too. Which probably did eat the plants of the time.

… or did speculation go too far.

Having followed geology and biology for more than 60 years, I have been impressed by a general trend for evidence to surface that things had occurred earlier than we currently thought.

henry said:

1. Gingras, M. K. et al. 2008. How fast do marine invertebrates burrow? Palaeogeography, Palaeoclimatology, Palaeoecology. 270 (3-4): 280-286.

So henry did you read the Gingras et al. paper or did you just copy and paste it from Morris?

Jim Thomerson said:

Having followed geology and biology for more than 60 years, I have been impressed by a general trend for evidence to surface that things had occurred earlier than we currently thought.

Well that is usually the only way it could change. Once a tetrapod is known to exist at time x, it could not have first evolved afterwards. Ditto most everything else. ;-)

OgreMkV -

Related, it occurred to me - and this is really, really obvious; I’m sure I’ve seen it but it never quite hit me before - that all accurately dated fossil finds give the minimum age of a lineage.

It has to be at least that old if we found and accurately dated the fossil, but there could be older ones out there that we haven’t found yet. Not too much older, obviously, but older.

As long as we’re conjecturing things, I was wondering if walking or walking-like behaviors may have been evolving from an earlier time than expected in some fish lineages. There are modern fish that “walk” on the bottom.

OgreMkV said:

This may be pure babble, but follow me here.

The date of first tetrapods would probably have to be pushed back even further.

I would suspect that this is a predator. 1) There were only simple land plants (at best) during this time period. A two meter animal like this would have a hard time surviving on hornworts. 2) It probably couldn’t swim well enough to catch larger fish (because of those large, stupid limbs sticking out from the side). 3) So it was probably a predator of other (smaller) tetrapods that couldn’t move as quickly because of size. (At this point, pretty much the only way to go faster was to be bigger, there wasn’t enough variation in limbs structure to produce sprinters and runners, etc) 4) So this ate tetrapods smaller than itself, so there must have been a pretty large population of those guys running around too. Which probably did eat the plants of the time.

… or did speculation go too far.

I would think that it would be more of a land-visitor, rather than a land-dweller, as at the time, there were only hornworts, mosses, fungi and the primitive land plants like Rhynia or Homeophyton, and the only other terrestrial animals were semi-microscopic arthropods.

That, and the first fossil evidence of terrestrial vertebrate herbivores date to the mid to late Carboniferous.

Henry -

Just FYI, I don’t personally follow a formal religion, but I have no problem with religion.

I do have a problem with creationist denials and distortions of science.

Glorifying God, finding Jesus, etc - as far as I’m concerned, that’s your own business.

DS said:

Robert wrote:

“Darwin based much of his work on the presumption of geology conclusions of long ages. So before biology evolution is discussed the geology issue must be settled.”

Wrong again genius. Doesn’t it get boring being wrong every single time.

FIrst, Darwin had no idea how old the earth was. In order for this theory to be correct, the earth had to be very ancient, now we know that it is. The “geology issue” was settled over one hundred years ago. Do try to keep up Robert. You can ignore all of the findings of the last two hundred years, but that doesn’t mean that anyone else has to.

I have a quote from Darwin in 1859 A.D. “ He who can read Sir Charles Lyell’s grand work and yet does not admit how incomprehensibly vast have been the past periods of time may at once close this volume” I suppose in reference to one of Darwins books but i can’t quote.

Well I would say to Charles that biology founded on a separate subjects ideas should close its claims to being a true study of biology. If one must accept other concepts before his biological concepts then one can say Darwin is being influenced by ideas beyond biological observations. He is admitting that his conclusions don’t work if other conclusions are not already accepted. Indeed without geology timeframes evolution conclusions are just plain wrong. He also seems to be saying to the reader you will not be persuaded by his ideas without prior persuasion of long ages concepts. AMEN. The creationist is already rightly suspicious. Biology that can not stand on its own merits should stand aside.

To Darwin in 1859 “incomprehensibly vast… periods of time” meant tens of millions of years, which was the scale Lyell was working on. That worried Darwin, because it didn’t seem to be enough time for evolution, and he was right to worry, because it wasn’t. But the period wasn’t tens of millions of years. That rough estimate is under by two orders of magnitude, but Darwin didn’t know that. It wasn’t until after his lifetime that an accurate estimate could be made.

So Darwin was right, even though he had no idea of how old the Earth is.

Robert,

Do you have any point to make here at all? Your only point seems to be that evolution cannot be accepted without geology? So what?

Once again, Darwin dod not know how old the earth was. His theory required a very ancient earth. The earth has indeed been determined to be very ancient. Darwin has been proven to be correct. Deal with it already.

Robert Byers said:

I have a quote from Darwin in 1859 A.D. “ He who can read Sir Charles Lyell’s grand work and yet does not admit how incomprehensibly vast have been the past periods of time may at once close this volume” I suppose in reference to one of Darwins books but i can’t quote.

Well I would say to Charles that biology founded on a separate subjects ideas should close its claims to being a true study of biology. If one must accept other concepts before his biological concepts then one can say Darwin is being influenced by ideas beyond biological observations. He is admitting that his conclusions don’t work if other conclusions are not already accepted. Indeed without geology timeframes evolution conclusions are just plain wrong. He also seems to be saying to the reader you will not be persuaded by his ideas without prior persuasion of long ages concepts. AMEN. The creationist is already rightly suspicious. Biology that can not stand on its own merits should stand aside.

Totally bogus argument! Since the various fields of study in science are always made stronger by references to other and very different fields of study, your statement is absolute nonsense. For example, we can compare how old the Earth seems to be with the estimated age of the entire universe. If they are the same age, or if the Earth appeared OLDER than the universe as a whole, that would be a blow to naturalistic evolutionary time scales. Instead we find the opposite, that the universe itself seems much older than the Earth within it. Hench astronomy AND geology AND biology all debunk the notion that the universe could be only a few thousand years old.

Biology that can not stand on its own merits should stand aside.

and thus religion…?

Ichthyic said:

Biology that can not stand on its own merits should stand aside.

and thus religion…?

Which brings us back to Robert’s moronic claim of how the 1st Amendment of the US Constitution stipulates that Creationism can be taught in science classrooms because it’s allegedly word for word true, but one can not teach actual science because actual science conflicts with and offends Robert’s personal view.

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