The disappearance from the face of the earth these ancient animals like dinosaurs may be due to the fact that smaller individuals that are able to survive a natural disaster, extinct or "transformed" in the form of birds in competition with baby dinosaurs larger sizes and mammals, as stated by the Swiss paleontologists from University of Zurich.
In an article published in the edition of Biology Letters, a team of researchers led by Marcus Claus highlight the fact that there is a huge difference in the size of the young and adult dinosaurs and large mammals on Earth today. Thus, the newborn son of a bishop is 22 times smaller than its mother, while any large reptile of the Mesozoic period was 2.5000 times their just born baby.
The maximum allowable size of the eggs, as the scientists explain, for all kinds of animals lay eggs, usually strictly limited thickness of the shell. Shell eggs can not be too thick, as it will not pass the required amount of air that can lead to the death of the embryo or contribute to its extremely slow development. That’s why even the largest eggs of dinosaurs could have a diameter greater than 20 centimeters long and 60 centimeters.
Such a restriction, as noted by paleontologists collected all young herbivorous and carnivorous dinosaurs at once in the same ecological niche after birth, which is significantly reflected interspecific and intraspecific competition.
To determine the diversity of species in each "weight class", the researchers compared all the known fossils of dinosaurs and the ancestors of birds. After that they built with the help of computer simulation ecosystem to the presence of ancient mammals and dinosaurs and observed changes in the position of small dinosaurs in ancient ecological niches that included young dinosaurs larger sizes.
Modeling clearly indicated that the lack of dinosaurs small and medium size was more to do with competition between lizards. However, in mammals such problems were noted, although they have not reached the dimensions of large animals because of competition with large dinosaurs, which they lost.
In addition to the young dinosaurs were fighting for resources and ancient warm-blooded animals. Kids mammals do not have to take an extra niche at an early age because they fed their mother’s milk, and then switched to the same food, eaten by their adult relatives. This became an additional competitive effect on small dinosaurs.
Scientists believe that 65,500,000 years ago, the last mass extinction of dinosaurs in the history of the Earth could survive only animals with a body weight not exceeding 25 kg. The absence of small dinosaurs "classical" types of the cause of extinction of giant lizards.