Thursday, January 19, 2006

Early evolution of the tetrapod ear - some shameless self-promotion

An article in today's Nature details the ear region of a 370-million-year-old fish called Panderichthys - and I'm an author! If you're not familiar with this fish, it is (for now) the most tetrapod-like lobe-finned fish known from complete body remains. It fits in between classic sarcopterygians like Eusthenopteron and the earliest known tetrapods such as Acanthostega and Ichthyostega.

What we have shown here is that the dramatic modification of the skull in the ear region began while the ancestors of modern tetrapods were still water-borne fishes. That is, they did not have all the requisite adaptations for life on the land. Consequently, we proposed that these modifications were retlated to some type of ventilation function (either passing air or water or both).

You'd probably think I'd say more about this, but you have no idea what a fill I've had of writing about this. Writing paper's for Nature is no easy task. They have to be short and to-the-point. Most importantly, you have to pack all the information you would put into a considerably longer paper into about 6 double-spaced pages - max! I re-wrote the manuscript nearly a dozen times to get it down to something snappy but still clear.

To that end, Nature has written a plain-language summary that should be accessible to all. The media likes to emphasize our functional model, which is by far the most speculative part of the whole paper. The main issue is that we can outline what sorts of changes are happening in the skull that 'set the stage' for later evolution that would eventually lead to a middle ear.


Caio de Gaia said...

Just curious, wasn't Tetrapoda redefined as a clade that doesn't include Ichthyostega and Acanthostega but only Amphibia and Reptiliomorpha? Can we still use tetrapod as an informal term for those things?

I'm always impressed at the things one can learn from a complete vertebrate skull. Wish we had more of those. I enjoy the way you slap faces at the end of your plain-language summary. Well, they deserve it.


Martin Brazeau said...


The definition of Tetrapoda depends on who you ask, to some degree. One definition includes the other and depends really on which system you favour.

I, myself, do not yet accept a crown-group definition of Tetrapoda: the common ancestor of all living tetrapods and all its descendends. This does eliminate Ichthyostega and Acanthostega because they had to have branched off before this ancestor existed.

However, the apomorphy-based definition (four-limbed vertebrates with digits) will grow increasingly problematic as more fossils are found that provide intermediate stages for the limbs.

So yeah, go ahead and use the term 'tetrapod'. We all know what you mean!


SteveF said...

Congratulations Martin. I'm just starting my PhD, so this gives me something to aim at!

Also, I really appreciate your efforts with GoP over at the Pandasthumb. If you have time, and despite the frustrations it may cause, I'd like to see you continue your responses. I'm learning a lot from them and picking up some useful references.

Frogtacular said...

Wow, I can't beleive it. You've managed to write a letter to nature article that is actually quite readable.

For this you are to be commended. Well done!

Martin Brazeau said...

Thanks for the kind words.

Posting repsonses to GoP has become rather exhausting, especially after my last response. He appears unable to properly negotiate the task of understanding the material he is dealing with. I'm not really going to entertain this any longer because it is actually not a fruitful discussion. There is no point to it. He is clearly not understanding what is going on and I can't really be bothered to continue a discussion with someone who hasn't even read the papers he cites. Evidence is not his game, it's selective use of citations that he has not read.

There are many reasons not to entertain GoP any longer. The main one being that he now carries a third corn shute.

frogtacular, I'm surprised you've found it readable! Many people have not been able to. Anatomy jargon is almost its own language and it takes a lot of work to pick up. I'm glad you could get through it!

OddCoincidence said...

Uppsala? Awesome.

I just caught your interview on the Nature podcast today. When Chris introduced you I stopped at the name, but then figured it couldn't be you cause he said you were in Sweden. But apparently you are. Nice work with the article!

Anyway, good to hear you're doing well, and that your research is panning out. I'll be checking the blog, now that I know it exists.

Regards from Montreal,

Louis Simoneau

Martin Brazeau said...

Hey Louis!

Good to hear from you, a fellow skeptic! Glad you caught the podcast and the article. Indeed, I have vacated Montreal for Sweden and the research is going quite well here.

Looking forward to having you come around here - more commentors will always be welcome!


SteveF said...

I do understand your reluctance to respond to GoP Martin. I've played around with creationists concerning my own area of research (Quaternary type stuff) and had a fair share of banging head against wall moments.

I think the trouble with GoP is the (false) sense of authority with which he posts. His most recent comment is an example of this:

"Do the large conflicts between Chang (2004) and the latest molecular research pose problems for the Coelacanth-Lungfish-Tetrapod trichotomy? And how does this affect the placement of putative tetrapod ancestors? Which line of evidence should be given more weight, particularly if both approaches boast low p-values? This also applies to the Afrotheria hypothesis, which is supported by high bootstrap values and SINE insertions, yet clashes with the latest fossil evidence."

To someone reasonably educated in science, your posts have shown GoP to be, er, somewhat loose with the facts. However, to the lurker comments like the above may be persuasive. Its such people (probably the majority of the populace) that concern me.

Sometimes I think the internet is more trouble than its worth!

Martin Brazeau said...

I may well respond in brief to GoP's latest post. However, I merely have to repeat my assertion that he has not read the paper he is citing, namely Chang (2004), which makes little reference to the issue of coelacanth, lungfish, and tetrapod interrelationships. It is, instead, more interested in the nature of dipnomorph interrelationships: that is, how are the most lungfish-like sarcopterygians and lungfishes themselves related to one another.

The topology obtained by Chang is almost irrelevant to the issue that GoP is talking about.

He also continues to ignore the fact that the most recent analyses of molecular data supports the favoured view of paleontologists.

SteveF said...

Thats cool Martin; I wasn't trying to pressure you into responding, more ruminating on the problem of faulty information on the internet. I see it as a real problem and one that is only likely to grow.