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Re: Dinosaur egg-laying contributed to extinction?



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
>>
>>
>>
>
>