gh DINOSAURS NEVER HATCHED THEIR EGGS

The more we learn about dinosaurs the more these extinct animals strike our imagination. They excite the constantly growing interest; however, the available sources of information are limited: fossilized bones, footprints and eggs. Non-specialists may tend to underestimate the value of fossilized eggs. Nevertheless, even the information about the eggs' size can be a material contribution to the study of the behavior of dinosaurs, which hatched out of those eggs in prehistoric times. V. Dolnik (Zoological Institute, Russian Academy of Sciences, St-Petersburg) has undertaken the study of the fossilized eggs and the egg laying. He has come to the conclusion that dinosaurs could hardly hatch eggs and bring up the babies.

The proportions of the living creatures' organisms are not arbitrary: the weight and mass of the internal organs, the thickness of the bones and the eggs size are proportional to the body weight. This dependency (allometria) comes out of experience and has been accurately defined for birds and reptiles. However, V. Dolnik had to determine the dinosaurs' eggs allometria independently based on the contradictory data from scientific research materials. The above results evidence that an egg of a one-kilogram dinosaur should have weighted 50 grams, and that of a 100-ton dinosaur should have weighted 10 kilograms. Therefore, the dinosaurs' eggs weighted significantly less than the birds' ones (in comparison to the body weight), the gap growing with the body weight increase: the extinct bird called Epiornis which laid 10-kilogram eggs weighted not more than a ton. However, the dinosaurs' eggs appear to be 7-9 times heavier than those of the modern reptiles. The reason is that in the course of evolution the dinosaurs' eggs evolved to be covered by a hard porous shell which increased the eggs' absolute size (other reptiles' eggs are covered by a skin shell). Apparently, large eggs covered by the hard shell ensured the competitiveness of the species.

If the size of the egg is known, its solidity can be calculated. The birds' eggs are hard enough to withstand the female's weight, that is why birds manage to hatch the eggs. Dinosaurs also laid solid eggs, but the point is that dinosaurs were much heavier than birds. Dinosaurs were unable to hatch the eggs: they would have simply broken them. The eggs at that time were alive, fragile, not fossilized and could not stand heavy pressure. Anyway, dinosaurs were reptiles and the reptiles do not sit on the nests. But did they take care of the babies?

So far this question has no answer, as it is impossible to find out the number of eggs a dinosaur used to lay per season. In fact a living being can spend only a limited amount of energy on the reproduction, the amount being also proportional to the body weight. This energy is normally spent on the mating behavior, construction of the nest, egg laying (or delivery), hatching and upbringing of the posterity. The scientists can only make guesses about the dinosaurs' mating behavior, dinosaurs did not hatch the eggs, but if the eggs were numerous, all the reproductive energy was spent on the egg laying. No energy was left for the upbringing of the babies. If the eggs were few (in comparison to the body weight), it can be assumed that the parents did protect and feed the babies. Nonetheless, if the care of the posterity was typical of dinosaurs, it was not inherent in all dinosaurs' species. The babies of a 10-ton dinosaur weighed 3000 times less, and such difference in the sizes, according to V. Dolnik, significantly impeded the upbringing and feeding of the babies in the nest and guiding them. Probably, dinosaurs used to guard the laying like contemporary crocodiles do.

V. Dolnik (whose speciality is ornithology) assumes that the light can be shed on the dinosaurs' egg laying in case some of the paleontologists apply an unbiased approach, collect only reliable data from the scientific literature and calculate new allometric equations. It is desirable that this scientist should not be an advocate of any theory on the dinosaurs' structure. V. Dolnik emphasizes that a lot of scientists arbitrarily interpret the research data; one and the same author may deliberately change the egg weight almost by ten times in the articles intended for different purposes, thus complicating the work of other researchers.

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