Tiktaalik had hind limbs!

January 14, 2014 • 9:46 am

by Greg Mayer

In a paper in press in the Proceedings of the National Academy of Sciences, Neil Shubin, Ted Daeschler, and the late Farish Jenkins describe the pelvis and partial hind limb of Tiktaalik roseae, the lobe-finned fish from the Canadian high arctic that they discovered in 2004 and described in Nature in 2006. Tikataalik is a transitional form from fish to tetrapods, and presents such a suite of advanced (for a fish) features that Neil dubbed it the “fishapod”. The newly reported finds show that Tiktaalik had a very substantial pelvic girdle and limb, which must have had a significant role in locomotion.

Of course, it’s not a surprise that Tiktaalik had hind limbs– most vertebrates do– but  the nature of the hind limbs in this, the most tetrapod-like of fish, is of especial interest. It’s been known for a while that Neil et al. had found the hind limb, and their publication on it has been eagerly awaited. The most important find, a pelvis and part of the associated limb, was actually found on the original holotype specimen (the one from which the species was described) found in 2004; four other isolated pelvises were found in later years. Since the first publication, preparator Fred Mullison has been working to free all the bones from the encasing rock.

Comparison of the girdles of Tiktaalik to those of Eusthenopteron  (a 'standard' lobe finned fish) and Acanthostega (one of the earliest known amphibians)
Comparison of the girdles of Tiktaalik to those of Eusthenopteron (a ‘standard’ lobe finned fish) and Acanthostega (one of the earliest known amphibians)

So, what have we found out? The pelvis is robust, with an ilium and pubis, and a large acetabulum for receiving what must have been a substantial femur. There’s no ischium (the third bone in a typical tetrapod pelvis). The Tiktaalik website has 3D scans of the pelvis which you can rotate to see the full morphology.

Tiktaalik pelvis from below: ilium on left, the rounded acetabulum for reception of the head of the femur, pubis on right.  The pubis is directed laterally.
Tiktaalik pelvis from below: ilium on left, the rounded acetabulum for reception of the head of the femur, pubis on right. The pubis is directed medially.

Only a portion of the hind limb was preserved: the intermedium, two radials, and several bony fin rays (lepidotrichia). We can tell from the acetabulum though that the femur must have been robust.

Hind limb of Tiktaalik from Shubin et al. 2014. The thin rays are lepidotrichia; the upper rectangular bone is the intermedium, the lower pair are radials.
Hind limb of Tiktaalik from Shubin et al. 2014. The thin rays are lepidotrichia; the upper rectangular bone is the intermedium, the lower pair are radials.

Here’s how the team summarized their findings:

Although no femur was found, Tiktaalik‘s fin rays and several other bones suggest the hind fin was comparable in size and complexity to the front fin. The shape and size of the hip socket reveal that the fin was capable of a wide range of movements, from swimming to supporting weight and rotating more like a tetrapod limb. But the overall structure of the pelvis is still more fish-like. Whereas tetrapods have a pelvis made of three parts, Tiktaalik‘s pelvis is still made of one, like fish. …

Overall, the mix of fish and tetrapod characteristics show us that the structures and mechanisms necessary for the invasion of vertebrate life on land evolved in the water first. Not only that, but before this discovery, we thought the front fins held the key to how vertebrates began to walk on land. The “front wheel drive” theory that fish dragged themselves out of the water with strong front fins and puny hind fins no longer holds. It appears that an “all-wheel” or even a “rear-wheel drive” system is a more appropriate analogy as the hind fins were just as important and may have even been involved in a walking behavior first.


Shubin, N.H., E.B. Daeschler and F.A. Jenkins, Jr. 2014. Pelvic girdle and fin of Tiktaalik roseae. Proceedings of the National Academy of Sciences in press. pdf

First two Images from the Tiktaalik website 2014 New Discovery page.

Farish A. Jenkins, Jr., 1940-2012

November 13, 2012 • 11:42 pm

by Greg Mayer

Farish A. Jenkins, Jr., Curator of Vertebrate Paleontology and Alexander Agassiz Professor in the Museum of Comparative Zoology at Harvard University, died on November 11, 2012. Farish made major contributions to vertebrate paleontology, functional morphology, and evolutionary biology. He had been ill with cancer for some time, but had continued to work productively, and his death came quickly following a recent reverse. (See update below.)

Farish Jenkins in the vertebrate paleontology collection of the Museum of Comparative Zoology, holding a skull of Massetognathus, a Triassic cynodont (an advanced mammal-like reptile) from the Chanares Formation, Argentina. Photo by Hilary Rosner, Tooth & Claw.

Although Farish published on many subjects, the part of his work likely to be of most interest to WEIT readers is that on transitional forms. Farish worked on three great transformations in the history of tetrapods, including two that have become classic case studies in the origin of higher taxa. First, he worked on the origin of mammals, often in collaboration with his  MCZ colleague, A.W. “Fuzz” Crompton. That the ancestors of mammals were to be sought among a particular group of fossil reptiles known as synapsids had been known since the 19th century. What Farish, Fuzz, and many colleagues helped to show was how this transition occurred, and how the bones of the reptilian jaw joint of synapsids moved in to the middle ear of mammals to become ear ossicles, while a new jaw joint, the mammalian jaw joint, evolved. It is a favorite tactic of creationists, even today, to ask how possibly could the jaw of a reptile come unhinged, and a new joint develop, with the reptile bones passing into the ear? Well, the answer is, we know exactly how they did it, because we have the fossils- read Crompton and Jenkins, and look at the pictures!  (For the latest on mammalian ear evolution, see this paper by Luo Zhe Xi.)

Farish was one of the triumvirate who, along with Neil Shubin and Ted Daeschler, described Tiktaalik, the fish-tetrapod intermediate from Arctic Canada that made the front pages of newspapers around the world when it’s discovery was publicly announced in 2006. Neil and Ted got most of the media appearances, but it was Farish who was the old hand at arctic paleontological exploration (in the video below, look for Farish at 1:45). Although describing Tiktaalik taxonomically and morphologically was but a small part of his copious output, Farish may be best remembered for this work.

Most recently, Farish and colleagues completed a monographic account of Eocaecilia, a caecilian with limbs (which they had named and briefly described years earlier). Caecilians (not to be confused with the edible variety) are a group of tropical amphibians which today lack limbs, and Eocaecilia is a form that is transitional from fully-limbed ancestors to the modern condition.

Eocaecilia micropodia (‘the tiny-footed dawn caecilian’) from Jenkins and Walsh, 1993.

Both Jerry and I knew Farish from our days at the MCZ. I last saw him on a visit a year or two ago, after he was diagnosed with cancer, but he was his usual voluble self; Jerry saw him at the MCZ just a few months ago. Always impeccably dressed and charming, he had the demeanor of what I imagine a retired officer of the Royal Horse Guards would be like. He helped organize and lead a superb graduate course on vertebrate paleontology (I cannot recall now whether I enrolled or just attended) in the comfortable environs of the Romer Library, named for one of his distinguished predecessors at the MCZ, Alfred Sherwood Romer. I do recall stories of Arctic fossil hunting, with high powered rifles a necessity, as one man stood guard for polar bears, while others peered at the rocks. In addition to his teaching duties in the Faculty of Arts and Sciences, Farish taught human anatomy at the medical school. His comparative and evolutionary approach was not only appreciated by medical students, but also provided an opportunity for vertebrate morphology graduate students, by either taking the course or assisting in its teaching (or both), to gain the experience and background in human anatomy that would allow them to go on and train generations of physicians, as well as commanding the much higher salaries found in medical school anatomy departments. The Nature News Blog has some nice recollections of Farish by Hopi Hoekstra, the MCZ’s curator of mammals. The science writer Hilary Rosner has posted an endearing reminiscence of her encounters with Farish, along with a number of fine photographs, at her blog, Tooth & ClawAs another MCZ colleague put it to me earlier today, “His lectures were legendary…He was a scholar and a gentleman, and truly one of kind.”

A symposium in Farish’s honor, Great Transformations, was held last June. Like Ernst Mayr, also of the MCZ, who got to attend and speak at his 100th birthday symposium, Farish too was able to attend and speak at this gathering to celebrate his achievements. I understand there is a festschrift of the contributions in the works, but unfortunately Farish will now not see it.

Update. More accounts and reminiscences well worth reading have appeared in the Harvard Gazette, Boston Globe, and at Postcardsfrom Farish.


Crompton, A.W. and F.A. Jenkins, Jr. 1973. Mammals from reptiles: a review of mammalian origins. Annual Review of Earth and Planetary Sciences 1:131-155.

Crompton, A.W. and F.A. Jenkins, Jr. 1979. Origin of mammals. Pp. 59-73 in J.A. Lillegraven, Z. Kielan-Jaworowska, and W.A. Clemens, eds., Mesozoic Mammals: The First Two-Thirds of Mammal History. University of California Press, Berkeley.

Daeschler, E.B., N.H. Shubin, and F.A. Jenkins, Jr. 2006. A Devonian tetrapod-like fish and the evolution of the tetrapod body plan. Nature 440:757-763.

Downs, Jason P., Edward B. Daeschler, Farish A. Jenkins, Jr., and Neil H. Shubin, 2008. The cranial endoskeleton of Tiktaalik roseae. Nature 456: 925-929.

Jenkins, Jr., F.A and A.W. Crompton. 1979. Triconodonta. Pp. 74-90 in J.A. Lillegraven, Z. Kielan-Jaworowska, and W.A. Clemens, eds., Mesozoic Mammals: The First Two-Thirds of Mammal History. University of California Press, Berkeley.

Jenkins, F. A., Jr., and D. M. Walsh. 1993. An Early Jurassic caecilian with limbs. Nature 365:246-250.

Jenkins, F. A., Jr., D. M. Walsh, and R. L. Carrol, 2007. Anatomy of Eocaecilia micropodia, a Limbed Caecilian of the Early Jurassic. Bulletin of the Museum of Comparative Zoology, 158 (6): 285-365. pdf

Luo, Z.-X. 2011.  Developmental patterns in Mesozoic evolution of mammal ears.  Annual Review of Ecology, Evolution and Systematics 42: 355–80. pdf

Shubin N.H., E.B. Daeschler, and F.A. Jenkins, Jr. 2006. The pectoral fin of Tiktaalik roseae and the origin of the tetrapod limb. Nature 440: 764-77.

WEIT review: Kevin Padian sucks me back into into the religion/science quagmire

April 1, 2009 • 7:06 am

Kevin Padian, a paleontologist at the University of California at Berkeley, has done pathbreaking work on the evolution of flight, and on other paleobiological issues.  He’s also been a stalwart defender of evolution against creationism, and is the president of the National Center for Science Education.

In the latest issue of Public Library of Science Biology (known as PLoS Biology), Padian has written a  review of Why Evolution is True.  I wish I could say I was pleased with it.  After all, Padian did start the review by praising the book:

First, make no mistake: this is a wonderful book, as far as the explanation of many of the interesting lines of evidence and case histories for evolution go. . . Coyne hits all the right notes, without over-dazzling the general reader with too many molecular complexities or obscure examples. This is a very readable, companionable work that takes its place alongside other fine recent explanations of evolution such as Evolution: What the Fossils Say and Why It Matters, by Donald R. Prothero [3], and Your Inner Fish, by Neil Shubin [4], as well as a great many Web sites that explain the evidence for evolution. It would be an excellent text for a freshman or non-majors course in evolution, or for a local book group.

So why am I grousing?  Because his review is not about the science — or even about the book. Rather, it’s about a book that he wanted me to write but that I didn’t.  Padian spends most of his review calling me to task for not emphasizing strongly enough that evolution is compatible with religious faith.

First, a scientific quibble.  Padian criticizes me for not using strict cladistic terminology:  we should not say, for instance, that amphibians evolved from fish because “fish” is a term reserved for an ancestor and all of its descendants — which is not strictly true because some descendants of early fish became amphibians, and, ultimately, reptiles, birds, and mammals. This is the same criticism that Eugenie Scott leveled at the book in her review in Nature (that’s no surprise, because Scott is executive director of the NCSE and a close associate of Padian).  I can see their point from a cladistic stand, but it’s not necessarily the best way to present evolution to the public.  Under cladistic terminology, no group could have evolved from any other group!  All of us (including Neil Shubin, the discoverer of  the transitional form Tiktaalik) call the aquatic, lobe-finned ancestors of tetrapods “fish”.   It’s common parlance, and not misleading to the public.  What would Padian call those lobe-finned ancestors?  At any rate, I don’t think using common parlance is a serious crime here; in fact, it makes things clearer.  So we can agree to differ on this (see the comments by Greg Mayer and Nick Matzke here).  But that’s not Padian’s main criticism.

Padian says that “truth” (as in the title of my book) “is a personal thing.”   And he complains that I have not explained to the readers what I mean by saying that something is “true”:

Based on the title of this book I would have expected a bit more engagement with the philosophy of knowledge. How do we know something is true, and what do we mean when we say something is true? What could make us abandon our claims, and realistically, would we ever do so?

But Kevin doesn’t seem to have noticed the following passage in the first chapter (page 16):

Because a theory is accepted as “true” only when its assertions and predictions are tested over and over again, and confirmed repeatedly, there is no one moment when a scientific theory becomes a scientific fact.  A theory becomes a fact (or a “truth”) when so much evidence has accumulated in its favor– and there is no decisive evidence against it– that all reasonable people will accept it.  This does not mean that a “true” theory will never be falsified. All scientific truth is provisional, subject to modification in light of new evidence. There is no alarm bell that goes off to tell scientists that they’ve finally hit on the ultimate, unchangeable truths about nature.  As we’ll see, it is possible that despite thousands of observations that support Darwinism, new data might show it to be wrong.

And on p. 222-223, at the end, I show why evolution qualifies as “true” under this definition, and also give examples of possible observations that could disprove evolution.

But his real point is the NCSE’s standing policy of courting religionists, as articulated by Eugenie Scott:  “This is not a problem that you can solve merely by throwing more science at it.”  You have to cater to believers.

Three points here:

1.  The Dover decision rested on throwing science at Judge Jones, not convincing him that you could believe in evolution and God, too.  You don’t have to be a believer to refute creationist claims or to show that they were inspired by religious belief.

2.  You can’t solve the problem without throwing science at it. That’s what I was trying to do. That’s what I was trained to do. So I’m trying to solve the part of the problem that I’m capable of addressing without hypocrisy.

3.  Twenty-five years of hard work by scientific organizations like the NAS and NCSE, involving pushing religion/science accommodationism, have had no perceptible effect in changing the public’s acceptance of evolution.  It stays at about 40-50%, no matter what. Yes, court cases are won, but minds don’t seem to be changed.  I have pondered this long and hard, and have concluded that these figures won’t budge much until the United States becomes, over what will be a long period, a more secular nation: much like the countries of western Europe.

What should I have written, according to Padian?  That “truth” is philosophical, not objective, and that we should recognize and respect the philosophical “truths” of the faithful:

Creationists—people who deny evolution because it conflicts with their religious precepts—often tell us that whether we accept a naturalistic or a supernatural explanation of the world around us is a philosophical choice: a belief. They’re not wrong. That first decision—what kind of “knowledge” is going to be privileged in your mind—is ultimately a question of belief, a leap of faith, a decision about truth, if you care to use the term at all. . . . .

. . . Coyne does a very good job in this book of presenting the actual evidence for evolution. He is less complete on the philosophy and methods that underlie science, particularly in specific disciplines. And one would have liked to see more
about dealing with people who are apprehensive about the “truth” of evolution.

But this is something I’m incapable of doing.  I can’t tell people that faith and science are compatible, because I don’t believe it, and I don’t want to be a hypocrite.  Nor do I want to pander to religion.  And I’m not so sure that it is a “philosophical” choice” or a “belief” “to “accept a naturalistic versus supernaturalistic explanation of the world around us.”  Is it a philosophical choice to take antibiotics when you have an infection, rather than calling on a shaman or Christian Scientist?  (I bet you do take antibiotics, Kevin–is that a philosophical choice?)  And is it a “philosophical choice” to say that AIDS results from drug-taking and a dissipated lifestyle rather than from a virus?  Is it a “philosophical choice” to believe that the world is 6,000 rather than 4.6 billion years old?  Well, if these are philosophical choices, one of them works and the other one doesn’t.

The postmodernist claim that accepting scientific rather than spiritual truths is simply a matter of taste is a claim of breathtaking inanity.  Science helps us understand the world — it works.  Religion can soothe us, but I don’t see it coughing up equivalent truths, nor have I heard a convincing argument for what “truths” faith presents to us, as opposed to those revealed by secular reason alone.  Somehow I can’t believe that in his heart Padian accepts this philosophical equivalence, but maybe I’m wrong.  What exactly is his position vis-a-vis the supernatural? Can cancer be cured by both shamans and chemotherapy? Is he perhaps saying that books defending evolution should go easy on those religious views from which he himself isn’t fully emancipated?

Finally, Padian makes the following statement:

All these are worthy and sensible statements. And yet Coyne begins his last chapter with the statement of an audience member to him after his public lecture: “I found your evidence for evolution very convincing—but I still don’t believe it.” Well, nothing says that our job is to convince people of the “truth” of evolution—I don’t think it’s my job—but we would like people to understand it.

This is a remarkable admission. Does it mean that The National Center for Science Education doesn’t care if Americans accept evolution?  All that money and work, just so people can understand a theory they reject?

Good new paper on the fish-tetrapod transition

March 19, 2009 • 2:17 pm

Thanks to Carl Zimmer for pointing out a new paper by Jenny Clack in Evolution: Education and Outreach: “The Fish-Tetrapod Transition: New Fossils and Interpretations.” This is a good paper for the non-scientist who wants to know more about the documentation of this important transition. In WEIT I wrote mostly about the Tiktaalik roseae transitional form, largely because a lot of work on that fossil was done by my colleague Neil Shubin. I was criticized by some for not mentioning the other important fossils in this sequence, and Clack’s article fills this gap very well. Highly recommended.fish

Darwin Day, Philadelphia. 1. I meet Ken Miller

February 14, 2009 • 6:00 am

Last night’s keynote talk at the University of Pennsylvania’s Darwin Symposium was given by Ken Miller, and had the same title as his book: “Only A Theory, Evolution and the Battle for America’s Soul.” Ken is undoubtedly the most tireless and effective opponent of creationism in America, a star witness for the prosecution in the Dover trial, and he also co-wrote our country’s most popular high school biology textbook, so I have always admired him a great deal. But the admiration is not unmixed. Ken is also an observant Catholic as well as an author and cell biologist, and his books, starting with “Finding Darwin’s God: A Scientists’s Search for Common Ground Between God and Evolution,” have always tried to alloy religion and science, endorsing the idea that science and faith are compatible.

I have been uncomfortable with this view, and finally criticized it in a book review in The New Republic, “Seeing and Believing.” Miller responded in a piece on Edge.org. We are both ardent defenders of (excuse the term) Darwinism, but definitely part ways when it comes to faith.

So I was quite excited (and a bit nervous) about sharing a platform with Ken. I knew he’d be a good speaker, because I’ve seen his talks on YouTube and, of course, his famous appearances (twice) on The Colbert Report. His evening talk didn’t disappoint. Miller is a lively, humorous, and humane speaker, and develops a great rapport with the audience.

Miller’s talk was a pastiche, covering the Dover Trial, the morphing of creationism into intelligent design, and the evidence for evolution from fossils (Tiktaalik featured prominently) and from the fusion of two chromosomes present in our common ancestor with other apes into the single second chromosome of humans. All good stuff, and extremely enjoyable.

It was in the last ten minutes that Miller took up the issue of evolution and God, and that is where I had to part company with him once again. Over the years Miller has tried several ways to reconcile these two areas, including positing God’s direct intrustion into evolution (in Finding Darwin’s God), and suggesting that the laws of physics were devised by God (in Only A Theory). Miller has also said he is a theist, so that God intrudes directly in the real world.

This time he used a different angle, saying that there was indeed design in nature, but it was not the same kind of God-mandated design proposed by ID-creationists. Rather, it was “design” wrought by natural selection. He hammered home this idea again and again, and I began to realize that a kind of subliminal inculcation of the audience was going on. After all, natural selection does not produce “design”—it produces apparent design. Why not just say that? It was the use of the un-adjectivized “design” that seemed to be sneaking God’s hand into Miller’s view. (He also stated unequivocally his certainty that evolution would yield creatures with high, human-like intelligence if the process were to begin all over again, a view that I criticize in “Seeing and Believing.”)

It seemed to me, and several others with whom I spoke, that Miller was trying to get some teleology into nature by using the term “design”. My friend Rick Grosberg opined that the term “design” was a semantic “wedge” that Miller was using to make biologists more open to the idea that God might have played a role in evolution. Regardless, this part of the talk made me quite uncomfortable. I actually Googled “design” during this part of the talk and found the following definition in Merriam-Webster’s website:

1de·sign           Listen to the pronunciation of 1design
1 a: a particular purpose held in view by an individual or group : he has ambitious designs for his son b: deliberate purposive planning <more by accident than design 2: a mental project or scheme in which means to an end are laid down. 3 a: a deliberate undercover project or scheme : plot b plural : aggressive or evil intent —used with on or against he has designs on the money. 4: a preliminary sketch or outline showing the main features of something to be executed the design for the new stadium. 5 a: an underlying scheme that governs functioning, developing, or unfolding : pattern , motif the general design of the epic. b: a plan or protocol for carrying out or accomplishing something (as a scientific experiment) ; also : the process of preparing this6: the arrangement of elements or details in a product or work of art 7: a decorative pattern a floral design.

All of these definitions have one thing in common: purpose and intent. To say that natural selection produces “design” is in effect saying that it yields something that is planned: that there is some foresight in the process. Why would anybody use such a word? I’ve heard evolutionists use “apparent design” or “the appearance of design” as results of selection, but never “design” by itself. If this is not intentional teleology, I’d urge Miller to stop saying this, as it clearly plays into peoples’ idea that there is some intentional design in evolution.

At any rate, after dinner I met Ken and we chatted about things. The first thing he said to me was that one of his friends advised him to break a beer bottle over my head, which was more than a little intimidating when imparted to me by a guy well over six feet tall looking down on my puny five-foot-eight self! But we discussed our differences, tried to iron out misunderstandings on both of our parts, and amiably shook hands. We will never agree on the science-versus-faith thing, but on most issues we are on the same side, and I admire him in many ways. I was glad that we met.