My OperaEgg Size Fatal for Dinosaurs
Thursday, April 19, 2012 7:27:08 AM
Even gigantic dinosaurs weighing up to 100 tonnes had tiny babies. The average titanosaur, the largest type of vertebrate that ever lived, was 2,500 times heavier than its newborn. A modern-day elephant mother weighs 22 times more than her calf.
The reason is simple. Dinosaurs were egg laying, and there are physiological limits to egg size. The embryo inside the egg needs air to breathe, so the egg shell must be sufficiently thin to allow gaseous exchange. Larger eggs need thicker shells, but the need of air imposes a maximal eggshell thickness.
Elephants nurse their youngs with milk, so that the young ones reach a certain size before they compete on resources in their ecological niche, while the tiny dinosaur babies begin to eat the same sort of food as their parents the day they leave their egg.
According to a new study published in Biology Letters limited egg size made dinosaurs more vulnerable to the intense pressures of the end-Cretaceous extinction about 65 million years ago.
Competition at smaller size classes, the authors suggest, drove dinosaurs to become bigger and bigger, and this created a lack of species that were small at maturity. Mammals and avian dinosaurs occupied those niches. If the catastrophe targeted large animals, but was less severe among small animals, then non-avian dinosaurs would have been doomed. The big dinosaurs disappeared, and there were no small non-avian dinosaurs left to quickly proliferate in the aftermath.
Reference:
Ontogenetic niche shifts in dinosaurs influenced size, diversity and extinction in terrestrial vertebrates
By Codron et al.
Biology Letters
doi: 10.1098/rsbl.2012.0240
In Norwegian:
The reason is simple. Dinosaurs were egg laying, and there are physiological limits to egg size. The embryo inside the egg needs air to breathe, so the egg shell must be sufficiently thin to allow gaseous exchange. Larger eggs need thicker shells, but the need of air imposes a maximal eggshell thickness.Elephants nurse their youngs with milk, so that the young ones reach a certain size before they compete on resources in their ecological niche, while the tiny dinosaur babies begin to eat the same sort of food as their parents the day they leave their egg.
According to a new study published in Biology Letters limited egg size made dinosaurs more vulnerable to the intense pressures of the end-Cretaceous extinction about 65 million years ago.
Competition at smaller size classes, the authors suggest, drove dinosaurs to become bigger and bigger, and this created a lack of species that were small at maturity. Mammals and avian dinosaurs occupied those niches. If the catastrophe targeted large animals, but was less severe among small animals, then non-avian dinosaurs would have been doomed. The big dinosaurs disappeared, and there were no small non-avian dinosaurs left to quickly proliferate in the aftermath.
Reference:
Ontogenetic niche shifts in dinosaurs influenced size, diversity and extinction in terrestrial vertebrates
By Codron et al.
Biology Letters
doi: 10.1098/rsbl.2012.0240
- http://rsbl.royalsocietypublishing.org/content/early/2012/04/12/rsbl.2012.0240.full
- http://www.foxnews.com/scitech/2012/04/18/shells-made-dinosaurs-egg-stinct-scientists-say/
- http://blogs.smithsonianmag.com/dinosaur/2012/04/how-eggs-shaped-dinosaur-evolution/
- http://www.nature.com/news/dinosaurs-grew-to-outpace-their-young-1.10465
In Norwegian:
Lindsey Pilatoicy360 # Friday, April 20, 2012 6:44:56 AM
Ole Nielsennielsol # Friday, April 20, 2012 7:43:07 AM
Best wishes!
Ole
Lindsey Pilatoicy360 # Friday, April 20, 2012 7:46:35 AM
Thank for your time. Here is a link to a picture.
https://www.facebook.com/photo.php?fbid=431370406879737&set=a.270185376331575.88474.100000203452570&type=1
Lindsey Pilatoicy360 # Friday, April 20, 2012 9:44:26 PM
Again, thank you for your time.
Ole Nielsennielsol # Saturday, April 21, 2012 7:07:27 AM
But as I said museum personnel are generally speaking nice people and very helpful.
Best wishes!
Ole
simoncito # Wednesday, May 16, 2012 10:08:05 PM
I find it hard to wrap my mind around the proposed model of evolutionary drift towards bigger and bigger mature individuals, though.
If those "bigger" species outcompeted those which remained smaller, why didn't they also outcompete birds and mammals going for the same resources? And why were there smaller (in maturity) non-avian dinosaur species too? Species that didn't survive the chicxulub impact and/or the Deccan trap crisis, while avian theropods and crocodilia did?
Brian Switek (in the blog post you linked to) asks that question (albeit in much better words) - it does seem like a valid point to make.
Ole Nielsennielsol # Thursday, May 17, 2012 7:43:33 AM