Sunday, 22 April 2012

Egg-Laying May Have Caused Dinosaur Extinction

An international team of researchers has found why and how egg-laying reproduction may have led to the extinction of dinosaurs.

Weighing in at four tons, the mother animal was 2,500 times heavier than its newly hatched dinosaur baby. By way of comparison, a mother elephant, which is just as heavy, only weighs 22 times as much as its new-born calf. In other words, neonates are already big in large mammal species.
After all, larger eggs require a thicker shell and as the embryo also needs to be supplied with oxygen through this shell, eventually neither the shell nor the egg can grow any more. Consequently, newly hatched dinosaur babies cannot be larger in the same way as in larger species of mammal.
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 a 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 kg animals to those that were occupied by the fully grown forms of over 30 tons.
“The consensus among researchers is that animals of particular body sizes occupy particular niches,” said study lead author Dr. Daryl Codron of the University of Zurich. “In the case of the dinosaurs, this would mean that a single species occupied the majority of the ecological niches while mammals occupied these through numerous species of different sizes.”

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