Pharyngula

Najash rionegrina, a snake with legs

It’s a busy time for transitional fossil news—first they find a fishapod, and now we’ve got a Cretaceous snake with legs and a pelvis. One’s in the process of gaining legs, the other is in the early stages of losing them.

Najash rionegrina was discovered in a terrestrial fossil deposit in Argentina, which is important in the ongoing debate about whether snakes evolved from marine or terrestrial ancestors. The specimen isn’t entirely complete (but enough material is present to unambiguously identify it as a snake), consisting of a partial skull and a section of trunk. It has a sacrum! It has a pelvic girdle! It has hindlimbs, with femora, fibulae, and tibiae! It’s a definitive snake with legs, and it’s the oldest snake yet found.

It’s described in a short paper that consists mostly of fine anatomical details. I won’t go into them, except to report the abstract and show you what these lovely bones look like.

It has commonly been thought that snakes underwent progressive loss of their limbs by gradual diminution of their use. However, recent developmental and palaeontological discoveries suggest a more complex scenario of limb reduction, still poorly documented in the fossil record. Here we report a fossil snake with a sacrum supporting a pelvic girdle and robust, functional legs outside the ribcage. The new fossil, from the Upper Cretaceous period of Patagonia, fills an important gap in the evolutionary progression towards limblessness because other known fossil snakes with developed hindlimbs, the marine Haasiophis, Pachyrhachis and Eupodophis, lack a sacral region. Phylogenetic analysis shows that the new fossil is the most primitive (basal) snake known and that all other limbed fossil snakes are closer to the more advanced macrostomatan snakes, a group including boas, pythons and colubroids. The new fossil retains several features associated with a subterranean or surface dwelling life that are also present in primitive extant snake lineages, supporting the hypothesis of a terrestrial rather than marine origin of snakes.

Here are the bones themselves.

i-f33b54a1f4ecc987dabcf5b473f6336c-najash_sm.jpg
(click for larger image)

a, Dorsal view. b, Ventral view. The left pelvic and limb elements show signs of healed traumatisms, with a large callus formation on the fractured femur. The disarticulated fibula is not visible in these views. Scale bar, 50 mm. Abbreviations: cav, first caudal vertebra; fem, femur; ili, ilium; isc, ischium; ly1?ly3, first, second, and third lymphapophyses; plz, sacral pleurapophysis; pub, pubis; r, rib; sav, sacral vertebrae; tib, tibia; tro, trocanter; psv, last presacral vertebra.

And a cladistic analysis places this animal as a clearly primitive snake.

i-da28cf6d3621dbb786c2bc5ed3c3dec9-najash_phylo.jpg
The result is expressed in a strict consensus of two equally parsimonious trees (tree length of 270 steps, ensemble consistency index of 0.526, and retention index of 0.654). Bremer support and bootstrap percentages are given in the nodes (see Methods and Supplementary Information). Reconstructions of the pelvis and hindlimb elements of Najash, Pachyrhachis and a boine snake are illustrated for comparison.

It must be rough being a creationist right now—the data against their mythology just never stop coming.


Apesteguía S, Zaher H (2006) A Cretaceous terrestrial snake with robust hindlimbs and a sacrum. Nature 440:1037-1040.


(you can also find more at The Lancelet)

Comments

  1. #1 Alejandro
    April 19, 2006

    It must be rough being a creationist right now–the data against their mythology just never stops coming.

    PZ, you are too optimist and don’t understand how their mind works. Expect creationists to come out at any moment saying that this is a confirmation of Genesis 3.14, in which the serpent is punished by God making it crawl on its belly (implying it had legs before the Fall).

  2. #2 PZ Myers
    April 19, 2006

    Oh, dang, right. They’re going to use this to date the Fall now.

  3. #3 Zombie
    April 19, 2006

    They’ve already dated the Fall, haven’t they?

    I’m guessing this will get classified by Creationists as just a lizard, not a snake at all, ignoring any similarities to ancient snakes. After all, whoever heard of a snake with legs?

    (A short primer on cladistics might be helpful to non-biologists like myself, by the way. Or did I miss that post?)

  4. #4 Rocky
    April 19, 2006

    I’m sure this just made two more gaps……..

  5. #5 Blake Stacey
    April 19, 2006

    They’ll probably try to spin the “it has commonly been thought” part to give the impression that this fossil somehow upsets some deeply held and central dogma, thereby indicating that All Darwinism Is Wrong.

    Yes, they have tried to date the Fall. By the Ussher chronology, it would have happened in 4004 or maybe 4003 BCE, depending on how long you figure Adam and Eve were happily galumphing around the garden not eating the fruit of the tastiest tree. You know, if you take that as a starting point and add up the successive generations — Adam, Seth, Enoch, etc. — up to Noah, you can show that the Great Flood happened right when the Egyptians were building their biggest pyramids.

    Oops.

  6. #6 Rocky
    April 19, 2006

    Also, as to “dating the Fall”, can’t wait to see the convoluted logic YEC’s use to get 6000 yr. out of the over 65 million years date of this fossil.

  7. #7 paperwight
    April 19, 2006

    Snakes! With legs! On a motherfucking plane!

    Sorry. Someone had to do it.

  8. #8 Anton Mates
    April 19, 2006

    You know, it’s always interesting to see how young a lot of the critters are that we naturally think of as below us on the Great Chain of Being. Snakes don’t get really snakey until the Cretaceous, most social insects don’t really take off until then too, but mammals were busy being fast & furry as early as the Triassic. We’re as “dinosaurian” as the dinosaurs!

  9. #9 vermontraccoon
    April 19, 2006

    Speaking for my species, Procyon lotor, all I can say is : “You humans is cuh-razy…”

  10. #10 dbpitt
    April 19, 2006

    Wow. I always thought god just went click and then the snakes lost their legs.

    By the way, have we still not figured out where turtles came from?

  11. #11 lt.kizhe
    April 19, 2006

    It must be rough being a creationist right now–the data against their mythology just never stop coming.

    Yeah, we wish. But look at the reactions to Tiktaalik, such as the YEC med student linked by Orac: http://www.homeschooledmedstudent.blog-city.com/latest_meaningless_discovery.htm

    By this logic, there can never be a transitional fossil — fossils morphologically intermediate between known groups are just the way they are, and indicate nothing about phylogenetic connections. Creationists claiming “no transitional fossils ever found” are being disingenuous: they’ve preemptively defined the concept out of existence!

  12. #12 Andrew
    April 19, 2006

    Behe: “Your ‘piddling’ fossil does nothing to disprove intelligent design. We have always thought it was possible for snakes to have pelvises, even when we said otherwise. Now, if you could find a snake with the snout of a pig, the wings of a bat, and feet with thirteen toes, THAT would be convincing proof of Darwinian evoltuion.”

  13. #13 MikeM
    April 19, 2006

    Is there a pygmy + dwarf version of them?

    (Sorry. Someone had to ask. It was just my turn. It won’t happen again.)

    I find it interesting that some were evolving their limbs away, while others where evolving them. What does that imply?

  14. #14 Andrew
    April 19, 2006

    Behe: “Your ‘piddling’ fossil does nothing to disprove intelligent design. We have always thought it was possible for snakes to have pelvises, even when we said otherwise. Now, if you could find a snake with the snout of a pig, the wings of a bat, and feet with thirteen toes, THAT would be convincing proof of Darwinian evoltuion.”

  15. #15 improvius
    April 19, 2006

    I’m guessing this will get classified by Creationists as just a lizard, not a snake at all, ignoring any similarities to ancient snakes. After all, whoever heard of a snake with legs?

    That’s pretty easy to figure out. For one thing, snakes don’t have upper vertebrae – lizards do. A legless lizard has stubs for hind AND front legs, whereas a snake only has hinds. I’m sure there are other obvious differences, but that was the first that came to mind. Of course, now we just have to find the “missing link” that demonstrates how snakes lost their upper vertebrae…

  16. #16 A.H.
    April 19, 2006

    This reminds me of a paper from a while back where the authors implanted beads coated with either fgfs or bmps into the sides of embryonic snakes. The area of tissue was competent to respond to the signal and the snakes grew little limb buds. Neat stuff.

  17. #17 wamba
    April 19, 2006

    By the way, have we still not figured out where turtles came from?

    It’s turtles all the way down.

  18. #18 Rocky
    April 19, 2006

    dbpitt , I believe I read that turtles were related to or descended from Aetosaurs. I’m sure one of the knowledgeable persons who visit this site can confirm or deny…….

  19. #19 craig
    April 19, 2006

    Wasn’t a transitional fossil in the hominid line reported this week too? I swear I heard it on some science podcast.

  20. #20 James G
    April 19, 2006

    No matter how much evidence you collect, creationists can always fall back on the “God planted the fossil record to trick people” argument.

  21. #21 Turnip
    April 19, 2006

    Hang on. Genesis says that God removed legs from the Snake as a punishment for tempting Eve. YECs claim all fossils date from the flood.

    So this fossil is more than a transitionary fossil. It refutes literal creationism to an even greater extent than anything else.

  22. #22 Meteor Blades
    April 19, 2006

    Literal creationism can’t be refuted because literal creationists always have my stepgrandma’s daily mantra to stand on: “God works in mysterious ways, his wonders to behold.”

    You can’t can’t can’t win the argument, only the battle to keep their stuff from being passed off as science.

  23. #23 beervolcano
    April 19, 2006

    Oh, in that case it’s a True Lizard and not a snake at all.
    That is all, carry on.

  24. #24 Christopher
    April 19, 2006

    Sorry to hijack your thread PZ:

    Aetosaurs are armoured somewhat pig-like archosaurs, related to crocs, dinosaurs and birds. Based on morphological evidence, turtles appear to have close affinities to several groups of parareptiles (non diapsid reptiles), most research focusing mainly on pareiasaurs and procolophonids. However, some molecular evidence may suggest an archosaurian affinity for turtles. So turtle origin is still very much up in the air, but for now I would trust the morphological data.

    Now back to your regularly scheduled creationist bashing.

  25. #25 Leon
    April 19, 2006

    This is really a drop in the bucket for what you guys need to fill the gaps in Darwinism! Everyone knows dragons are supposed to be the transition from dinosaurs to birds (Archeopteryx being a forgery), so producing a mere snake with legs is child’s play! WHERE’S THE DRAGON FOSSILS???

    (Nah, they probably won’t trot out that arguement, but we can always hope…)

  26. #26 Dabodius
    April 19, 2006

    Where did they get the genus name? Nachash (ch as in Bach or loch) is Hebrew for “serpent,” as in Genesis 2.
    Until another specimen is found, creationists could say this was The Nachash of the story, “the most subtil beast of the field,” who was said to have started out with legs.

  27. #27 Hairy Museum Matt
    April 19, 2006

    Legged snake fossils have already been used to date the Fall, and, by extension, Creation:

    Kissil, J. 1997. “Evidence for creation of the earth during the Mesozoic era,” Journal of Irreproducible Results 32:6 p. 23.

    “Based on the fact that Pachyhachis [sic] problematicus is from the Cretaceous period (135,000,000-70,000,000 years ago) this would place the formation of the earth at about this time (+/- 45 years and 6 days).

    “This finding is in contradiction to previous suggestions placing the creation of the earth either 10 to 20 billion years ago or a mere 5757 years ago.”

  28. #28 Kayigo
    April 19, 2006

    I just looked at the blog of the “home schooled med student”. She has a run on how micro evolution does not prove macro evolution that is appalling.
    On another note, did anyone see the ID letter to the Lancet calling for a debate on the “pros and cons of Darwinism”?
    http://www.thelancet.com/journals/lancet/article/PIIS0140673606684201/fulltext
    I am trying to find out who this Noel Johnson person is. Since he comes from near Seattle, he has to be linked to the Discovery Institute somehow.

  29. #29 Zombie
    April 19, 2006

    Since he comes from near Seattle, he has to be linked to the Discovery Institute somehow.

    Speaking as a reality-based Seattle-ite, aaaaaaaaaaaaaaa-breath-aaaaaaaaaugh.

  30. #30 CCP
    April 19, 2006

    as for turtle origins (diapsid? archosaur? parareptile?), I hope it turns out to be procolophonoids.
    It’s so much fun to say it.

  31. #31 JW Tan
    April 19, 2006

    Zombie said:

    (A short primer on cladistics might be helpful to non-biologists like myself, by the way. Or did I miss that post?)

    Yes please!

  32. #32 Siv Volk
    April 19, 2006

    “Until another specimen is found, creationists could say this was The Nachash of the story, “the most subtil beast of the field,” who was said to have started out with legs.”

    Dabodius, firstly I need to squee over the language bit.

    But, if the Bible says God got rid of the serpents’ legs, the skeleton wouldn’t have legs, since they were removed, and obviously if the Biblical progenitor snake had its legs removed, so did all its descendents. Because any modification of a creature by God affects its descendents.

    At which point someone can introduce them to Lamarck, and let them know that they’re getting warmer.

  33. #33 Kayigo
    April 19, 2006

    Zombie: Sorry, I didnt mean to imply that all Seattlites are DI’ers. Just the ones writing letters to Lancet to support the “controversy” over “Darwinism”.
    Actually, my brother lived in Seattle until recently, and he wrote this http://6-bleen-7.livejournal.com/40036.html#cutid1
    in response to the Lancet article. He says it better than I could.

  34. #34 JP
    April 19, 2006

    The “home schooled med student” is horrifying, almost as scary as a snake with feet coming at you.

  35. #35 Virge
    April 19, 2006

    Now the Myers was more subtil than any other beast
    that abideth in the garden, from the greatest to the least…

    Back to the Garden

  36. #36 craig
    April 19, 2006

    On another note, did anyone see the ID letter to the Lancet calling for a debate on the “pros and cons of Darwinism”?

    Pros and cons? Well lets see…
    Pro: we get to have lifeforms that are more complex than the simplest possible one.
    Con: some of them are creationists.

  37. #37 JLem
    April 19, 2006

    Why must we assume that this fossil shows the process of losing limbs? How do we know that this fossil doesn’t show the independent evolution of limbs from a limb-less ancestor? I think it shows definitively that lizards evolved from snakes. Likewise, that Tiktaalik fossil clearly shows that fish evolved from terrestrial terapods. *sarcasm* (or is it *facetiousness*?)

  38. #38 Interrobang
    April 19, 2006

    Dibodius, Siv, I noticed that right away too. Then again, I’m a fan of the Israeli band Hadag Nakhash. A quick Google search suggests that “najash” is the Spanish-language transliteration of the Hebrew “nakhash,” but aside from that, I’ve got nuthin’. PZ, can you shed some light on this? I like biology, but I love linguistics…

  39. #39 Bob O'H
    April 20, 2006

    “No matter how much evidence you collect, creationists can always fall back on the “God planted the fossil record to trick people” argument.”

    As Terry Pratchett commented, He was just messing around with the pleistocene.

    Bob

  40. #40 Dabodius
    April 20, 2006

    Not to carry this too far, Siv Volk, but just for phun…

    “…if the Bible says God got rid of the serpents’ legs…”
    It doesn’t; it says he and his progeny were cursed to crawling (it says nothing about Mrs. Nachash, whose progeny they would have been, too.) So the legs of The Original Nachash could have stayed on, paralyzed — and this could be him!! What if it talks?!? I feel a cheesey horror movie coming on…
    Interrobang, I suspect you’re right about the transliteration. It would be an obvious choice for an archaeo-snake.

  41. #41 Zombie
    April 20, 2006

    Sorry, I didnt mean to imply that all Seattlites are DI’ers.
    Oh, I know, it’s just frustrating to have Seattle associated with such loons in the first place. You’d expect the DI to be located in a more stereotypically third-world part of the country, but the world does not always conform to our prejudices. 🙂

  42. #42 PZ Myers
    April 20, 2006

    Here’s what the article says about the origin of the name:

    Etymology: From Hebrew Najash, the legged biblical snake; rionegrina, for Río Negro Province, Argentina, where the fossil was found.

  43. #43 qetzal
    April 20, 2006

    After all, whoever heard of a snake with legs?

    Exactly! We get different types of snakes and different types of lizards, but you have never seen a snizard!

    😉

  44. #44 PZ Myers
    April 20, 2006

    We get different types of snakes and different types of lizards, but you have never seen a snizard!

    Maybe not, but I have seen a “lake”.

  45. #45 ezkerraldean
    April 20, 2006

    (slightly different topic)

    does anyone know about the aistopods? (devonian ambphibian snake-thingys). Is there any fossil evidence for their ancestry?

  46. #46 Sergey Romanov
    April 20, 2006

    They will claim they have already addressed this:

    http://www.answersingenesis.org/docs2/4250news3-20-2000.asp

    😉

  47. #47 MrDarwin
    April 20, 2006

    Let’s face it, the creationists and IDers will only accept a species as “transitional” when we can show them a living, breathing critter that is half-fish and half-monkey, joined together at the waist, like those taxidermic monstrosities you see on display at the Ripley’s Believe It Or Not! museums.

  48. #48 Leon
    April 20, 2006

    Actually, my brother lived in Seattle until recently, and he wrote this http://6-bleen-7.livejournal.com/40036.html#cutid1
    in response to the Lancet article. He says it better than I could.

    Except he says that “Until the last century or so, practically everyone in the world believed that the Earth is flat!”, which is wrong. A spherical Earth has been well accepted for centuries, especially (but not only) in educated circles.

  49. #49 IndianCowboy
    April 20, 2006

    After all, whoever heard of a snake with legs?

    Exactly! We get different types of snakes and different types of lizards, but you have never seen a snizard!

    LOL I just made a post on my blog today about ‘snizards’. There’s actually an entire genus of african ‘snizards’ showing various degrees of snake-ishness. Click my name for more info.

  50. #50 themaiden
    April 21, 2006

    Ahem… as some have suggested may be the case.

    Even if it could be shown that snakes at one time had legs, this actually fits within the creationist model. The loss of features like legs is a type of degeneration, which is the opposite of molecules-to-man evolution (which requires new genetic information for advancement)–see Beetle bloopers for background.

    And…

    AiG is cautious about comparing this fossil snake to the serpent in Genesis 3:14. First, we really don’t know much about the serpent’s anatomy anyway. Yet we can offer a reasonable guess that it apparently was once able to crawl or walk; after the serpent was cursed, it was pronounced that “on thy belly shalt thou go,” suggesting that it previously moved using appendages.5 Also, this fossil probably resulted during Noah’s Flood, an event that took place about 1,500 years after the serpent was cursed to crawl on its belly.

    Both quotes are from AiG– http://www.answersingenesis.org/docs2006/0421legs.asp

  51. #51 Drgns77
    April 23, 2006

    I’m new to this whole Evo/Id debate and have a couple questions. Does anyone have any undisputable evidence for evolution? Or undisputable evidence for God? Also, if there is no undisputable evidence would that make a person have faith or belief to think one or the other is right? Thanks for any info or links!

  52. #52 AaronVV
    April 30, 2006

    Looks like you guys are having a pretty good discussion about this snake thing. Quick question: does anyone have any pictures of the fossil other than just the one shown? I’d be particularily interested in an actual picture of the site where it was found, and maybe a layout of where the partial skull was in relation to the partial piece of its body. Thanks!

    As for Drgns77 post, I would say the greatest evidence for God’s existence is that fact that things happen which are contrary to science/nature. They are often referred to as miracles, and many people discredit them. Things such as a man rising from the dead, people being healed with but a prayer(which still happens), and the complete and utter change in people’s lives when they believe in God(society would call this going from unmoral or unethical to being a good or moral person) are all convincing proofs to me that there is a greater power at work than humans and nature. I’d be happy to chat more with you about this if you’d like. stealthy_monkey@hotmail.com

    Note: Don’t just take my word for it. Examine both sides of the evidence. Watch speakers who believe in both views. Use reason and logic to come to your decision. But like I said, I’d be happy to chat. Shoot me an email.

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