Let’s look at some animals!

February 20, 2012

An important new paper is out:

R. Kent Sanders and Colleen G. Farmer.  2012.  The pulmonary anatomy of Alligator mississippiensis and Its similarity to the avian respiratory system. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology (advance online publication). doi:10.1002/ar.22427

(It’s paywalled, naturally, but let’s just assume that everyone who reads this blog is affiliated with a big university and has access.)

First of all, congratulations to the authors on doing this properly: publishing a proper paper (sixteen pages) to follow up their big-splash Science paper of just over a year ago.  As Mickey Mortimer has shown, follow-through rates when people publish in Science and Nature are generally not at all good, and it’s always encouraging to see an exception.

Here’s the abstract:

Using gross dissections and computed tomography we studied the lungs of juvenile American alligators (Alligator mississippiensis). Our findings indicate that both the external and internal morphology of the lungs is strikingly similar to the embryonic avian respiratory system (lungs + air sacs). We identified bronchi that we propose are homologous to the avian ventrobronchi (entobronchi), laterobronchi, dorsobronchi (ectobronchi), as well as regions of the lung hypothesized to be homologous to the cervical, interclavicular, anterior thoracic, posterior thoracic, and abdominal air sacs. Furthermore, we suggest that many of the features that alligators and birds share are homologous and that some of these features are important to the aerodynamic valve mechanism and are likely plesiomorphic for Archosauria.

The main reason I want to post this (apart from the fact that it’s an important finding) is because someone had to blog David Marjanovic’s classic response on the Dinosaur Mailing List (quoted with permission, since David doesn’t have his own blog):

See, this is the kind of thing where I’m totally baffled that it wasn’t figured out a hundred years ago, or 120 or 130.

I suppose the logic that has prevented people from dissecting crocodilian lungs for so long went like this:

1) Crocodilians are reptiles.
2) So, crocodilians have reptile lungs, not mammal lungs or bird lungs.
3) What are reptile lungs like? Let’s dissect the nearest reptile and find out!
4) We’re in Europe, so let’s just take the nearest lacertid, perhaps the nearest “colubrid” and maybe the nearest viperid and cut them open.
5) <snip> <snip>
6) Hooray! We’ve figured out what reptile lungs are like!
7) Textbook describes and illustrates generic non-varanid squamate lung as “reptile lung”.
8) Everyone believes it is known what reptile lungs are like.
9) Everyone believes it is known what crocodilian lungs are like, because crocodilians are reptiles.

Ceterum censeo Reptilia esse nomen delendum.

If you must keep the name, follow Joseph Collins and restrict it to Squamata or Lepidosauria. Otherwise, destroy it. Kill it with fire.

So true.

We could draw a whole lot of conclusions from this analysis, but let’s just concentrate on one: look at animals.  See how they behave.  Then cut them open and see what’s inside.  Don’t assume.  Don’t guess.  Find out.  To quote the splendid motto of the Kirkcaldy Engineering Works, “FACTS, NOT OPINIONS”.

Seriously.  Who’d have though there was a Science paper and an Anatomical Record paper just in cutting open an alligator and having a poke around in there?  Sometimes, science doesn’t progress by paradigm shifts; sometimes it progresses just by looking at things.

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12 Responses to “Let’s look at some animals!”

  1. confusedious Says:

    Terrific paper, I’ll be sure to grab a copy (fortunately, affiliated with a large University).

    On this, have a look at the following link to another blogger relating to bird evolution, it may make you chuckle.

    http://patman023.wordpress.com/2012/02/17/sometimes-evolution-sucks/

  2. hypnotosov Says:

    I’m floored, how can there be a crocodile in every naturalist collection (and several in most zoos), yet we didn’t know this?!

    I don’t think the group reptiles is completely useless though, even if it is a mess. It provides a useful shorthand for explaining what Pterosaurs and Ichtyosaurs are to people who have never even heard the word Archosaur.
    Flying/swimming reptiles from the time of Dinosaurs is understandable even for a complete layperson, without requiring further explanation or resorting to (inherently false) comparisons.


  3. same goes for bone growth diagrams in text books. Apparently, all animals have mammalian bone growth patterns….

    AAAAAAAAAAAAAAAAAAAAAAAAAAAARGGHGHHHHHH!!!!!!!!!

  4. David Marjanović Says:

    same goes for bone growth diagrams in text books. Apparently, all animals have mammalian bone growth patterns….

    And mammalian cartilage, the one without blood vessels in it. Damn size squeeze at the origin of Mammalimorpha.

    ===============================

    I don’t think the group reptiles is completely useless though, even if it is a mess. It provides a useful shorthand for explaining what Pterosaurs and Icht[h]yosaurs are to people who have never even heard the word Archosaur.

    Precisely not.

    “Reptiles” conveys “like lizards”. Pterosaurs and ichthyosaurs are not like lizards. As shown above, even crocodiles are not like lizards!

    Superficially, pterosaurs and ichthyosaurs probably have more in common with each other than with lizards. It’s even possible they’re more closely related to each other (and crocodiles and dinosaurs – including birds, I have to stress it again) than to lizards.

    Besides, you’re probably talking to people who can’t tell a lizard from a salamander… might as well start from scratch and explain what an amniote is, what a sauropsid is, what a diapsid is and so on, it won’t take any worse.

    …*headdesk* I remember reading “salamanders are amphibians, not lizards” in a popular article a few years ago. So I googled that exact phrase, with quotation marks on… and got 111 results. *headdesk*

    Even people as influential as J. “K.” Rowling don’t know salamanders aren’t lizards. Check out the first result of the search I just did.

    Flying/swimming reptiles from the time of Dinosaurs is understandable even for a complete layperson

    No. You think so, and they probably think so, but it’s not at all true.

  5. David Marjanović Says:

    Heh. My automatically generated WordPress avatar has seldom been so appropriate. =8-)

  6. Mike Taylor Says:

    Even people as influential as J. “K.” Rowling don’t know salamanders aren’t lizards. Check out the first result of the search I just did.

    (Odd to see the quotes around the “K.”? They sent me to Wikipedia where I learned that she doesn’t have a middle name, or didn’t until she adopted one for publishing purposes.)

    Come on, though! There is a long and honorable tradition of using the word “salamander” to denote a mythical creature that lives in fire, and ofter resembles a lizard more than an amphibian. Objecting to that makes no more sense that objecting to the use of “drake” to indicate a dragon rather than a duck.


  7. I, uh, don’t have access. *sob*

  8. Matt Wedel Says:

    Zach–try this first. If you still can’t get it, drop me an email.

  9. Mike Taylor Says:

    I, uh, don’t have access. *sob*

    Silly Zach! Don’t you realise that there is no access crisis If only we would have the basic decency to listen to our betters, we could end this destructive conflict.

  10. David Marjanović Says:

    There is a long and honorable tradition of using the word “salamander” to denote a mythical creature that lives in fire, and ofter resembles a lizard more than an amphibian.

    Where I come from, Salamandra salamandra is actually called the “fire salamander” (…isn’t it in English as well?) because it crawls out of wood piles when you set them on fire, and traditional superstition claims that this real animal likes fire and withstands it without damage.

  11. David Marjanović Says:

    there is no access crisis

    *headdesk* The hon. Member for Wantage is no better informed than the average moron on the Internet, and no more aware of it.

  12. hypnotosov Says:

    “Where I come from, Salamandra salamandra is actually called the “fire salamander” (…isn’t it in English as well?) because it crawls out of wood piles when you set them on fire, and traditional superstition claims that this real animal likes fire and withstands it without damage.”

    It’s called that in Dutch too, it seems to be the common name in most European languages, but whether that is a reference to it crawling out of fires or it\s distinctive colour I don’t know. It certainly wouldn’t be the first time the story came after the name :-)

    “No. You think so, and they probably think so, but it’s not at all true.”

    You may be right, I may be underestimating that most people still think “lizard” when they hear reptile.


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