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Transcript by http://www.newsy.com BY XIAONAN WANG ANCHOR CARISSA LOETHEN Scientists say dinosaurs' egg-laying may have led to their own mass extinction. Discovery News explains. "Larger mammals can have larger babies, but dinosaurs could not due to the physical limitations of laying eggs ... When a catastrophic event wiped out larger species 65.5 million years ago, mammals were better able to recover." According to Australia's ABC, an adult Titanosaur hatchling, for example, was nearly 2,500 times bigger than its infant. Fox News notes, about 65 million years ago, dinosaurs were completely wiped out during a nuclear winter after a meteorite smashed into Earth. A researcher explains why this event was the last straw for these giant creatures. "That was not a problem for 150 million years but as soon as something happens that takes away all the large species so that only small species remain ... you are gone as a whole group." Why couldn't dinosaurs lay bigger eggs? Bits of Science has the reason: "...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. " Scientists say small dinosaurs were in competition with one another and with small mammals. That ultimately pushed them into extinction. The Telegraph describes the tough scenario for young dinosaurs. "Growing up, the youngsters had to compete in several size categories with adults of other animal groups for food...This meant that all the small and medium animal size categories supported by the natural environment were "occupied", leaving no room for smaller dinosaur species in which to thrive..." Although the new model of dinosaurs' extinction makes good sense, a biologist tells the journal, Nature it will be challenged. "..we are going to see a lot of debate over how accurate these models really are." According to Time Magazine, Russian scientists say they've just discovered 40 fossilized dinosaur eggs that are the biggest ever found. But some are skeptical that the eggs are nothing but rocks to attract attention.