Tiktaalik makes another gap

Paleontologists have uncovered yet another specimen in the lineage leading to modern tetrapods, creating more gaps that will need to be filled. It’s a Sisyphean job, working as an evolutionist.


This creature is called Tiktaalik roseae, and it was discovered in a project that was specifically launched to find a predicted intermediate form between a distinctly fish-like organism, Panderichthys, and the distinctly tetrapod-like organisms, Acanthostega and Ichthyostega. From the review article by Ahlberg and Clack, we get this summary of Tiktaalik‘s importance:

First, it demonstrates the predictive capacity of palaeontology. The Nunavut field project had the express aim of finding an intermediate between Panderichthys and tetrapods, by searching in sediments from the most probable environment (rivers) and time (early Late Devonian). Second, Tiktaalik adds enormously to our understanding of the fish-tetrapod transition because of its position on the tree and the combination of characters it displays.

Here’s the beautiful beastie as preserved:

a, Left lateral view; b, dorsal view with enlargement of scales; and c, ventral view with enlargement of anterior ribs. See Fig. 3 for labelled drawing of skull in dorsal view. Abbreviations: an, anocleithrum; bb, basibranchial; co, coracoid; clav, clavicle; clth, cleithrum; cbr, ceratobranchial; ent, entopterygoid; hu, humerus; lep, lepidotrichia; mand, mandible; nar, naris; or, orbit; psp, parasphenoid; ra, radius; suc, supracleithrum; ul, ulna; uln, ulnare. Scale bar equals 5 cm.

The analysis of the fossil clearly positions it as an intermediate: it has a more mobile skull/neck than a fish, and although its limbs are clearly fin-like, they also have features that presage the digits of tetrapods.

The lineage leading to modern tetrapods includes several fossil animals that form a morphological bridge between fishes and tetrapods. Five of the most completely known are the osteolepiform Eusthenopteron; the transitional forms Panderichthys and Tiktaalik; and the primitive tetrapods Acanthostega and Ichthyostega. The vertebral column of Panderichthys is poorly known and not shown. The skull roofs (left) show the loss of the gill cover (blue), reduction in size of the postparietal bones (green) and gradual reshaping of the skull. The transitional zone (red) bounded by Panderichthys and Tiktaalik can now be characterized in detail. These drawings are not to scale, but all animals are between 75 cm and 1.5 m in length. They are all Middle–Late Devonian in age, ranging from 385 million years (Panderichthys) to 365 million years (Acanthostega, Ichthyostega). The Devonian–Carboniferous boundary is dated to 359 million years ago.

The limbs alone have a whole paper dedicated to them. Tiktaalik‘s limb is third from the right in the diagram below, and you can see how it still has the fin rays of its predecessor, Panderichthys, but also has a robust bony axis with smaller bones branching off of it—it’s not quite the clear digits of Acanthostega, but it’s a step in that direction.

Unlike other tetrapodomorph fishes (1), Tiktaalik has reduced the unjointed lepidotrichia, expanded the radials to a proximal, intermediate and distal series, and established multiple transverse joints in the distal fin. The fin also retains a mosaic of features seen in basal taxa. The central axis of enlarged endochondral bones is a pattern found in basal sarcopterygians and accords with hypotheses that a primitive fin axis is homologous to autopodial bones of the tetrapod limb. In some features, Tiktaalik is similar to rhizodontids such as Sauripterus. These similarities, which are probably homoplastic, include the shape and number of radial articulations on the ulnare, the presence of extensive and branched endochondral radials, and the retention of unjointed lepidotrichia. Figures redrawn and modified from Glyptolepis, Eusthenopteron, Panderichthys, Acanthostega and Tulerpeton.

Those limbs tell us something about the evolution of limbs. Tiktaalik was definitely not a terrestrial animal, but had developed muscular, bony limbs and a strong pectoral girdle that had helped it prop itself up on the substrate, perhaps even holding itself partly out of the water. Those jointed digits were capable of extension and flexion, splaying out when they were pressed against the ground. That simple function, of spreading out to increase the surface area of limb contact, could be the precursor to the flexibility we now have in our hands.

a, b, Anterolateral view. c, d, Ventral view. a, c, Resting posture with the fin partially flexed at the antebrachium. In this position the radius is slightly more flexed than the ulna. b, d, Resistant contact with a firm substrate entails flexion at proximal joints and extension at distal ones. The shoulder joint is flexed by ventral muscles, including the trans-coracoid muscle. The elbow is flexed (d, arrow 1), with slight pronation of the radius (d, arrow 2) and rotation of the ulna (d, arrow 3). The transverse joints distal to the ulnare and intermedium are extended (d, arrows 4).

Lancelet has more.

As does Carl Zimmer, of course.

Ahlberg PE, Clack JA (2006) A firm step from water to land. Nature 440:747-749.

Daeschler EB, Shubin NH, Jenkins FA (2006) A Devonian tetrapod-like fish and the evolution of the tetrapod body plan. Nature 440:757-763.

Shubin NH, Daeschler EB, Jenkins FA (2006) The pectoral fin of Tiktaalik roseae and the origin of the tetrapod limb. Nature 440:764-771.


  1. Lago says

    Amazing. Looking at that, and knowing it is still basically a fish, blows my mind. You really do not expect to see something looking like that and still having fins instead of feet…

  2. Great White Wonder says

    I can just hear the creationist murmuring, “Yes, but how do you get from something to that to an animal that is incapable of swimming — like a human?!?!”

  3. llewelly says

    Inspiring. Now all we need is the plush animal version –
    Teddy Tiktaalik.

  4. wÒÓ† says

    This fossil is clearly a hoax. Someone took a fish fossil and a muskrat fossil and stuck them in the same box.

    If you do not think this is possible, how is it there are PYGMIES + DWARFS??!

  5. says

    Anyone know what “tiktaalik” means? It’s obviously a word in one of the Eskimo-Aleut languages.

  6. Johnny Vector says

    And I was just thinking it’s been a while since Carl Buell posted anything on his blog. I think this creature is calling his name.

  7. says

    Dan, it means “large shallow water fish.” (There’s an article on the NYT webpage about the discovery which gives the translation.)

  8. says

    googling “tiktaalik” turned up a hit on it as the common name for Lota lota, which seems to be a sort of freshwater cod.

    of course, I defer to anyone who actually knows anything about either fish or Inuktitut.

  9. Apikoros says

    I am curious as to the origin of the bone that forms the scapula. It looks like it originates behind the gill cover. Is it a modified rib or a modified gill arch?

  10. says


    If you mean the large, blade-like bone of the shoulder girdle, that’s the cleithrum, not the scapula. It’s actually a dermal bone that has nothing to do with the gill arches or ribs at all.

    The cartilage-derived scapula later invades the space occupied by the scapula, that’s why it’s easy to confuse these.

  11. Sean Foley says


    The scapula is derived from the cleithrum, which is an element of the pectoral girdle.

  12. Sean Foley says

    Oops. Not derived from, but allied with. It’s produced by endochondral ossification in the embryo.

  13. says

    I love those vertebrates; gotta admit, I’m partial to them.

    I wouldn’t characterize the work as Sisyphean, PZ, because Sisyphus never eroded the mountain into smaller peaks, whereas science will always narrow the gaps. (Though some nay-sayers will never be satisfied unless science provides a childish and improbable list of “begats,” with one fossil proven to be the mommy of another and the grandmother of the next. Sheesh.)

  14. Apikoros says

    Hmm… well, after posting that, I went off to do a little Googling and found this from an earlier incarnation of Pharyngula! Which implies (obviously, correction appreciated) that the scapula is not a bone, but rather a fusion of two bones together. It also implies that the scapula and coracoid bones have different (and mixed) origins. Alas, I am still confused :-(

  15. Keith says

    Since I live in the Canadian Arctic, allow me to say boo-ya! go home team!

    Tiktaalik is Inuktitut for “big freshwater fish”. It’s the modern term for the burbot (freshwater ling).

  16. Apikoros says

    Martin, Sean,

    Thank you! So it is independent of the ribs and gills and evolves de novo. I’d always thought that it, like the jaw, was a modification of a pre-existing part (usually a safe bet).

  17. Rocky says

    Damm, I love this web site PZ!
    Always get the hottest press on the newest finds.
    Keep it up and thank you.

  18. says

    Your title should be ‘Tiktaalik makes two gaps’, surely, unless of course Shubin et al. have cracked the mystery of abiogenesis.

  19. says


    Well, the “shoulder blade”, if we should call it that, is de novo only in a deep ancestral sense. Tiktaalik and early tetrapods are both expressing an ancestral feature of all bony fishes, which is to have a shoulder blade made from dermal bone. That is, it comes from bone that is deposited in the skin during development. The cleithrum is found in all bony fishes, and is variable in things like acanthodians, spiny shark-like fishes that preceded the origin of bony fishes.

    It’s “de novo” only in a very ancient sense, but Tiktaalik and all other bony vertebrates get it from their last commmon ancestor, at the latest.

    What later happens, for instance in mammals, is that the bone called the scapulocoracoid, which forms the shoulder joint, begins to take over the space occupied by the cleithrum. You basically get the same shape but the tissue forming it is different. In mammals, it is bone derived from a cartilage precursor within the body, rather than in the skin.

  20. Michael Geissler says

    Heard about this find on the way to work today on (Australian) ABC Radio National. Had to smack my head in frustration when the announcer said something like “fish that moved onto land and developed legs and a backbone”. Second smack followed when she said “scientists have known this happened but haven’t been able to prove it until now”. No wonder there is so much misinformation about basic science in the community.

  21. The Brummell says

    Michael Geissler:

    Sounds depressing. Has the US recently had a fling with Australia? Seems that happened recently with Canada, and now we have federal funding agencies rejecting grant applications for not clearly demonstrating that ID is not a scientific theory.

    Have you tried contacting ABC Radio National? Do they have a feedback link somewhere on their webpage?

  22. Apikoros says


    Check! I think “independently developed” would be better than “de novo”. I can certainly see the adaptation of skin plates to other functions and early fish certainly had enough bony plates in the skin!

  23. vandalhooch says

    Praise FSM!

    This post comes exactly one day before I give the first lecture on evidence for evolution to my sophomores. Yes I said first. I typically spend 7 to 8 weeks cover evolutionary theory and implications. The tradeoff is the loss of the typical “March through the phyla”. Both are valuable, but evolutionary theory is clearly more critical for student learning.

    The fact that Pee Zed relays the find just as I’m updating the lecture slides and notes demonstrates that the FSM is truly an Intelligent Designer!


  24. says

    Your title should be ‘Tiktaalik makes two gaps’, surely, unless of course Shubin et al. have cracked the mystery of abiogenesis.

    Nope, just one more gap. If Tiktaalik comes between A and B, it preserves the gap after A but creates a new one after B:

    A [gap] B — > A [gap] T [gap] B

    Just one more gap.

  25. says


    but aren’t you really saying that T has destroyed the A-B gap and created two new but smaller gaps (A-T; T-B) in its place?

  26. Chris Nedin says

    Regarding the Australian broadcast. There is a also a piece up on the ABC website. However the tag line is AFP (Agence France-Presse). So in (some) defence of Australia it appears the piece was a foreign-sourced report and the ABC simply regurgitated it.

  27. says

    Sisyphean job? Cool with me, as long as they keep funding our rock pushing… ;O)


  28. JohnnieCanuck says

    It’s always nice to find another cousin to add to our genealogy charts. Let’s see 380 Myears; maybe 10 years average per generation, (order of magnitude). 38 million grand parents between us and these ancient ones. Maybe tens of thousands removed, of course.

    I think my daughter has grandpa Tiktaalik’s costae.

  29. says

    but aren’t you really saying that T has destroyed the A-B gap and created two new but smaller gaps (A-T; T-B) in its place?

    Obviously for antievolution purposes each individual fossil’s life span occupies an entirely negligible amount of time, and is therefore best represented as a point. Putting a point between two other points on a line does not change the distance between the original two points. In other words, it is an immutable law of nature that in paleontology, total gap-ness is conserved in the fossil record.

    Would you like a smiley with that?

  30. Azkyroth says

    Even more impressive is a recently identified transitional form between mammals and reptiles. This organism has a stunning blend of the traits of both groups. Diagnostically mammal characteristics include the presence of hair and mammaries, while typically reptilian characteristics include cold-bloodedness, a virtually undeveloped cerebral cortex, a smaller and more primitive heart, and a forked tongue. An official taxonomic designation has not been selected for the species, but “Fasceophila vulgaris,” “Misanthropopsychosis belial,” and “Troglodyta macroscelidoides” have been suggested.

  31. says

    The reviewers that denied Alter’s grant application should now hang their heads further in shame, given this research going on right in (our) own country.

  32. says

    This organism has a stunning blend of the traits of both groups. Diagnostically mammal characteristics include the presence of hair and mammaries, while typically reptilian characteristics include cold-bloodedness, a virtually undeveloped cerebral cortex, a smaller and more primitive heart, and a forked tongue.

    Ironically, although there is only one member of this species known and its habitat is shrinking fast, it was denied a place on the endangered species list by Bush appointees at the EPA.

  33. Paul in LA says

    “Since I live in the Canadian Arctic, allow me to say boo-ya! go home team!” –Keith

    The specimen was FOUND IN THE TROPICS. Or at least that’s where it died.

    How’s that endless summer treating you?

  34. Rick Randall says

    Hasn’t Duane Gish ever heard about Urochordata or Cephalochordata, which have primitive notochords (precursor to an actual vertebrate) and only one set of Hox genes (like the inverterbate animals)?

    No, wait. . . that probably isn’t mentioned in the Authorized Version (i.e., King James) Bible or the Revised Standard Version Bible and so “doesn’t count as evidence”.

  35. Rudy says

    That is bull shat, It still leaves more Gaps, not to mention, that there useing a bunch of Fantasy art lol I bet the dateing comes back messed up lol

  36. says

    It’s clear to me that God wanted us to find this transitional fossil in 2004 so that it could be announced soon after Kitzmiller v. Dover discredited Intelligent Design. After all, God should be taken on faith, not squeezed into anti-scientific nit-picking!

  37. Jenn says

    Although research on Tiktaalik is in its more preliminary stages, I am hopeful that this specimen does prove to be a missing link. However, I am doubtful that any creationist will ever be satisfied with any evidence provided by the scientific commnunity. Even if every creature that had ever existed on Earth was found, documented in detail, and the entire theory of evolution was proven true, they would still say they don’t “believe.” You don’t have to believe in facts for them to be facts. However, you have to believe in faith for it to be faith. I believe it is unfair to approach facts as you would faith, and I believe it is equally unfair to approach faith as you would facts. They are completely unrelated, and quite frankly I don’t see what all the fuss is about. If evolution is true, then maybe God was a little more elaborate about “creating” all creatures great and small. I guess we will all have to revise our “poof and then there was life” view of God. It seems God is by far more complex than we ever thought, and this complexity is in keeping with the Bible, Koran, and other religious documentation. Most of the creationists also forget that the Bible and other books were written by more primitive people who didn’t fully understand what they observed and described the events as best they could. I’d hate to imagine how a person from a few thousand years ago would describe a car or a jet.

  38. Azkyroth says

    On that note, does anyone else think Ezekiel 10 sounds like he’s describing a UFO encounter?

  39. says

    There are many reasons why Tiktaalik cannot be greeted with the enthusiasm expressed by most contributors to this site. (1) The imbricate ribs of both Tiktaalik and Icthyostega do not make for mobility and to the best of my knowledge are not known in any (fully) terrestrial animal, alive or extinct. (2) The ribcages of these animals are unlike each other. (3) If Tiktaalik was on the way to walking on land, it cannot be transitional to Acanthostega since the latter was fully aquatic. (4) There is a large morphological gap between the pectoral fins of Tiktaalik and the forelimbs of Acanthostega/Icthyostega (as noted by Ahlberg & Clack). (5) There is an even larger gap between the respective rear appendages. (6) The fossil does not fulfil Darwinian predictions, which were that the gap between Panderichthys would be filled by an animal approaching the ‘rear-wheel drive’ condition – Tiktaalik is emphatically front-wheel drive (cf Nature 438:1145). And (7) tetrapod tracks have been found in sediments predating Tiktaalik. This is not to deny that Panderichthys and Tiktaalik are probably related, and therefore that the fossil has some (but relatively minor) evolutionary significance. More details may be found at http://www.earthhistory.co.uk/technical-issues/tiktaalik-roseae/.

  40. windy says

    Steven Robinson writes:

    The gap between the pectoral fin of Tiktaalik and the front foot of Acanthostega is large, as Ahlberg and Clack note. The gap between the pelvic fin of Tiktaalik and the hindlimbs of both Acanthostega and Icthyostega is so large that the authors omit to comment on it…

    Tiktaalik makes more and more gaps!!! OMG!

    If Tiktaalik was on the way to walking on land, it cannot be transitional to Acanthostega since the latter was fully aquatic.

    Of course it can. Don’t know if it is, but nothing to stop the descendant species from adapting slightly more or less aquatic lifestyles.

    Here is a recent report of a monkfish 380 metres below sea-level (Laurenson 2005):
    One of the monkfish was observed to move along the seabed for several metres at a time by walking. Several “walks” were observed. The gait involved both the pelvic and pectoral fins and the body and tail were lifted clear of the seabed.
    There is no reason to ‘think evolution’ when observing such behaviour. It’s just an example of how wonderfully unconventional life can be under water, as if whoever designed it was a non-conformist, a person who habitually subverts stereotypes.

    That’s just nutty. Of course there is reason to “think evolution” when we see a species with some apparently extensive adaptations to life on the sea bottom.

  41. MG says

    ‘Paleontologists have uncovered yet another specimen in the lineage leading to modern tetrapods, creating more gaps that will need to be filled. It’s a Sisyphean job, working as an evolutionist.’

    So yet again we find ourselves with more gaps in our theory than ever before. Somehow we still need to find proof that tigers are related to daffodils but that proof keeps getting weaker. How long before somebody else works out that this critter going straight from gilled fish to ear-bearing crocodilian reptile is in contradiction to the belief that fish became amphibians and then reptiles? Either it shows the long held belief to be wrong or it is not a transition at all. Still, it lets us carry on our belief that we are all mutant fish so we’ll put it in the text books and blast our school children with it to make sure they swallow the evolution pill, same as we did with Piltdown Man, Nebraska Man, Eohippus – Equus evolution and all the other ‘proofs’ for evolution that have since been proven wrong themselves. Note that the drawings above are only artist impressions and cunningly arranged to look like a progression. That should fool the masses nicely.

  42. ATCjpb says

    I would like to ask you to do a little more research on this latest “find.” Those Creationists are tricky and clever sometimes. They like to use our own science against us. The scientists in the article state that the fossil is from the Late Devonian period which puts the creature around 375 million years old. I would like to make sure that this dating is acurate through at least 2 dating meathods.(It would be rash to assume that the scientists had already confirmed this, because that would be unrefutable evidence and they neglected to mention this in any scientific journals I have seen.) In the past Creationists have used such ranges of dates (produced through different tests on the same material) to argue that the item cannot be catagorized scientificly through such results. If we are only looking at age of the rock to date this “find” then we are in for a difficult argument. The rock is said to be fossilised sandstone which cannot be tested for it’s age other than saying this layer is from the_____age and therefore any fossils found in it are also from this period. But dating fossils from those periods also must yield a date consistant with that claim or the sturdyness of the claim breaks down.
    I am only mentioning this now as a caution for over-the-top excitement about this “find.” If the dates are not consistant with the time period that this fish must fit into to be labeled a true transitional form, then we have a long road to victory. I would remind you that there are virutally no [scientificly] solid transitional forms illustrating primate to man. They are all so far either declared hoax’s or are so vauge that they are no longer popular as arguments. This vaugness extends to and includes the previously submitted transitional forms like the Archaeopteryx which displays only visual similarities and not biological resembelance to a reptile. Because of this biologists are now somewhat divided on the history of this magestic extinct bird species.
    If you read this far I am impressed and would like to thank you for your attention. I only say this to advise you to hold “facts” loosly. There is a lot of excitment around these new discoveries and the tendency to want to stick-it to the Creationists can be great, but let science prevail, and the truth will show itself. If this is a transitional fish then great, but I don’t really have much of a problem adding another species of fish to the catalog of new ones that we are finding every year that are still alive.

  43. brbradbury says

    Oh, please. Missing links don’t exist. They are excuses for Creationists to not believe in the evidence of how the planet, actually, works. All I see in the fossil record is a continuum. Even modern humans are changing. The wisdom teeth are becoming more, & more degenerative.

  44. kyz says

    YO….. Evolution is a theory…… it doesn’t have any knowledge of where we’re going after we die…. there’s no source of mercy, feelings or emotions that connect with our soul……. it has no answers to the way we live….. If evolution is correct then why are we wearing clothes..?? the simple fact of truth is that Adam and Eve sinned and saw themselves as naked and were ashamed…. they were ashamed of there nakedness…..

    umm…. I don’t see lungfish wearing clothes or knowing right from wrong, do you???

    God bless…. and I hope and pray you find the truth of your existance!!!!

  45. says

    This really very interesting that this creature predicted!

    The power of a theory is not only its explanatory power but also its predictive power.

    Now there are two more “gaps” to fill…..

  46. Duane Hagins says

    very interesting story dealing with the depiction of the very first link between man and Aquadic beings. I was delightited to see the mesh between the years in account and the adaptation to man. there weer a couple of segments dealing with timelines and skeletal photographs of more recent finds. This was enlightening to me.

  47. Thinker says

    “…it was discovered in a project that was specifically launched to find a predicted intermediate form…”
    I find it interesting that they were specifically looking for this and low and behold, they found it. That leads me to question it’s authenticity. It’s like reading something for a specific meaning and finding it there. If you go looking for something specific, of course you’re going to find, and interperate it the way you want it to be. This goes for creationist and evolutionist alike.

  48. says

    Not thinking at all, more like.

    What was predicted was that there was a place and time, given the place and time of other fossils, where we would expect to find an intermediate…not every detail of the anatomy of said fossil. Accusing the authors of faking it is rather contemptible. You can find published photos, you can write to the authors and ask permission to examine it (as many scientists do), and you can see it for yourself.

  49. truth machine says

    I find it interesting that they were specifically looking for this and low and behold, they found it.

    Damn but that’s stupid … the same would apply to every experimental result that bore out a prediction.

    That leads me to question it’s authenticity.

    That leads anyone intelligent to think you aren’t.

    It’s like reading something for a specific meaning and finding it there.

    No, it’s nothing like that. Do you have some expertise in paleontology on the basis of which you have an alternative interpretation? Is there anything in this article that you can factually challenge?

    If you go looking for something specific, of course you’re going to find, and interperate it the way you want it to be.

    Uh, no, it took hard work and a lot of time to find this fossil, and they almost didn’t.

    This goes for creationist and evolutionist alike.

    So if a creationist goes looking for a rabbit fossil in pre-Cambrian strata, he’s bound to find one?

    It’s one thing to think, and quite another to think rationally; the latter requires a certain amount of introspection and skepticism about one’s own thoughts, lest one produce the sort of moronic spew you did.

  50. Ichthyic says

    wait, i thought this was xmas time, not easter?

    why are all these old threads getting resurrected?

  51. truth machine says

    why are all these old threads getting resurrected?

    Because they’re linked to in current articles; duh.