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Re: Dinosaur egg-laying contributed to extinction?



Marcus Clauss has written a guest post for my blog dinosaurpalaeo in
which he explains some of the press' more fundamental
misunderstandings. First author Daryl Codron has further explanations
in a comment.

I urge all to read this before further speculating based on press mistakes.

http://tinyurl.com/Codronetal2012

Best
HM
___________________________________
Dr. Heinrich Mallison
Abteilung Forschung
Museum für Naturkunde - Leibniz-Institut
für Evolutions- und Biodiversitätsforschung
an der Humboldt-Universität zu Berlin
Invalidenstrasse 43
10115 Berlin
Office phone: +49 (0)30 2093 8764
Email: heinrich.mallison@gmail.com
_____________________________________
Fere libenter homines id quod volunt credunt.
Gaius Julius Caesar



On Wed, Apr 18, 2012 at 3:41 PM, Robert Schenck <schenck.rob@gmail.com> wrote:
> Fascinating article, like a few others here have commented, their
> hypothesis seems a little more sophisticated than it appears at first
> glance.
>
> I would think that their model is what really needs to be examined in
> order to fully critique their idea. It sounds like they are saying
> that newly hatched large dinos are clearly in a different niche than
> their parents, and that they're competing with the smaller dinos.
>
> But how is this going to drive them both to extinction? Usually (and I
> am not saying always) when two species compete, there ends up being a
> balance, OR one gets pushed out of the niche, and occasionally one of
> the competitors will go extinct. Normally a population biologist would
> address this by looking for morphological divergence as a result of
> niche competition. Often this type of divergence shows up as changes
> in feeding mechanism morphology.
> So do we see changes in the feeding morphology, the mouth-parts and
> head, of smaller dinosaurs co-incident with the spread of things like
> sauropods? I've never heard this before.
>
> Rather, different sauropods have varied heads and mouth-parts,
> possibly suggesting that they were competing against each other (if
> they're derived from niche-competition in the first place, which would
> require positively demonstrating that such competition occurred
> between them).
>
> Also, and I haven't read the article and we all know that
> news-articles are extremely poor sources of information, the Mesozoic
> is an astoundingly long period of time. What's true at the end of the
> Cretaceous was true throughout. Seems like the dinosaur radiation
> shouldn't've ever occurred if their hypothesis is correct.  They ran a
> computer model to, er, model this. My understanding is that population
> biology models, including the type that would look at competition,
> would be run on the span of generations or decades, not Eons.
> If their model shows dinosaurs crashing in after generations (or hell
> even after  a million years), then we know it's wrong, clearly they
> made it through this hurdle for millions and millions of years.
> These are all testable hypotheses that they're bringing up, should be
> interesting to see what happens.
>
> Also, the authors, per the popular article anyway, say that the small
> dinosaurs became birds. But this is only true for one small set of
> dinosaurs, and many of the small dinosaurs in that set that didn't
> become birds didn't survive.
>
> I think most people on this list, like myself, will notice that this
> idea of theirs sounds very much like the old way things were done in
> paleontology, that dinosaurs were inherently inferior, that they were
> doomed from the start to give way to more advanced mammals as only a
> matter of time (the idea that there are Grades of life). It sounds
> like that's really what they're saying, that Dinosaur biology utterly
> dooms them.
>
>
> On Wed, Apr 18, 2012 at 5:49 AM, Erik Boehm <erikboehm07@yahoo.com> wrote:
>> It seems to me the argument by the authors is more nuanced than their title 
>> suggests.
>>
>> "Many species occupy one niche each; one species occupies many niches
>> In addition, new-born mammals occupy the same ecological niche as their 
>> parents: As they are fed with milk directly by the mother, they do not take 
>> any niche away from smaller species. With large dinosaurs, however, it was 
>> an entirely different story: They did not only occupy the adults’ one niche 
>> during their lifetime, but also had many of their own to pass through – from 
>> niches for animals with a body size of a few kilos and those for ten, 100 
>> and 1,000-kilo animals to those that were occupied by the fully grown forms 
>> of over 30,000 kilograms."
>>
>> As others have pointed out, other egg laying reptiles did survive (egg 
>> laying mammals also survived), vivipatrious dinos did die out.
>>
>> I think they are suggesting that the difference in size between offspring 
>> and adults requires different ecological niches for different stages of 
>> development in the same species.
>> Thus if one niche becomes untenable, the species dies out, and the other 
>> niches are left vacant.
>> Mammals generally care for their young until they are able to survive on 
>> their own in the same niche as the adults.
>> Birds seem to do this too - although mammals have seemingly more refined 
>> mammary glands for feeding infants, while birds have seemingly crude 
>> regurgitation of food.
>>
>> In that system, if one niche becomes untenable, one species dies and the 
>> other niches remain filled by the birds/mammals occupying them.
>>
>> If the parents are able to feed the young, I don't think egg laying factors 
>> into it. If the parents are not able to, then the limits of egg size 
>> exacerbate the difference in size between the offspring and the giant 
>> parents, making it more likely that the one species occupies different 
>> niches in its lifetime.
>>
>> So I guess the hypothesis would be that parental feeding in dinos generally 
>> stopped before the young occupied the same ecological niche as their parents.
>>
>> Perhaps the reliance on flight forc
>> and as a side effect forced birds to care for their young until the young 
>> occupied approximately the same niche as their parents?
>>
>> So I guess the question is: how much evidence is there that adolescent 
>> dinosaurs occupied different niches from the mature adults in each of the 
>> major dino lineages?
>> The article/abstract just seems to assume they did due to size difference.
>> Do I recall correctly that there is evidence of age segregation in sauropod 
>> herds?
>> You might have a herd of fully mature adults protecting very young 
>> offspring, but then other herds composed entirely of adolescents of similar 
>> sizes?
>>
>>
>>
>> --- On Tue, 4/17/12, Jura <pristichampsus@yahoo.com> wrote:
>>
>> From: Jura <pristichampsus@yahoo.com>
>> Subject: Re: Dinosaur egg-laying contributed to extinction?
>> To: "Dinosaur Mailing List" <dinosaur@usc.edu>
>> Date: Tuesday, April 17, 2012, 7:22 PM
>>
>> From: Jura <pristichampsus@yahoo.com>
>> To: "dinosaur@usc.edu" <dinosaur@usc.edu>
>> Sent: Tuesday, 17 April 2012 10:03 PM
>> Subject: Re: Dinosaur egg-laying contributed to extinction?
>>
>>
>> Another paper that seems to be out of touch with the actual inferred ecology 
>> of the Mesozoic (i.e., it once again assumes that the K/T event was the end 
>> of the dinosaurs, instead of the end of 75% of all life on Earth).
>>
>>
>>
>> Also, no mention in the news story about how other reptiles were able to 
>> survive the K/T, or why viviparous plesiosaurs and mosasaurs bit the bullet.
>>
>>
>> Jason
>>
>>
>> http://reptilis.net
>>
>>
>> "I am impressed by the fact that we know less about many modern [reptile] 
>> types than we do of many fossil groups." - Alfred S. Romer
>>
>>
>> ________________________________
>>>> From: Ben Creisler <bcreisler@gmail.com>
>>>>To: dinosaur@usc.edu
>>>>Sent: Tuesday, 17 April 2012 9:44 PM
>>>>Subject: Dinosaur egg-laying contributed to extinction?
>>>>
>>>>From: Ben Creisler
>>>>bscreisler@gmail.com
>>>>
>>>>
>>>>A news release from the University of Zurich. The paper in Biology
>>>>Letters has not been posted yet on the website.
>>>>
>>>>Egg-laying beginning of the end for dinosaurs
>>>>
>>>>http://www.mediadesk.uzh.ch/articles/2012
>> torben_en.html
>>>>
>>>>
>>>>Biology Letters website:
>>>>http://rsbl.royalsocietypublishing.org/content/early/recent
>>>>
>>>>
>>>>
>>>
>>>
>>
>
>
>
> --
> Robert J. Schenck
> Kingsborough Community College
> Physical Sciences Department
> S332 ph# 718-368-5792
> Follow Me on Twitter: @Schenck
> KCC Class Schedule on Google Calendar: http://tinyurl.com/mqwlcy