How long has it been since elephant birds lived?

10.04.2003 20:17

The largest egg in the world

Dr. Ralf Breyer Public Relations and Communication
Johann Wolfgang Goethe University Frankfurt (Main)

What significance does it have for the life of dinosaurs? / Location Madagascar / Just in time for Easter the egg lies in its nest in Bonn / 73rd Annual Meeting of the Paleontological Society

Who lays the biggest egg in the world? Among today's animals, it is the ostrich. Among the fossil animals it may well have been a dinosaur - one would assume.

But that is not correct! In fact, the largest known eggs were laid by the extinct elephant birds or Madagascar ostriches. These ratites, of which the largest species Aepyornis maximus reached about 3 m in height, lived in Madagascar since the end of the Tertiary 2 million years ago and were the largest land animals on this island. They were gradually exterminated by the indigenous people and had disappeared before the Europeans appeared.

Fossil eggs of Aepyornis maximus are known in few specimens. The cast of one of the first finds is currently being presented in the GoldfuƟ Museum of the University of Bonn - suitable for Easter.

The egg is of particular interest not only because of its size, 31 cm in length and around 9 liters, it also raises the question of how large eggs can or must be compared to body size and weight. For comparison: the fossil egg is about twice as long and has seven times as much content as an ostrich egg. And: the egg from Aepyornis weighs as much as 190 chicken eggs!

It seems natural for large birds to lay large eggs, and the elephant bird, with an estimated live weight of almost 500 kg, or half a ton, is arguably the largest bird that has ever lived.

Compared to the largest dinosaurs, which could easily have weighed a hundred times, or 50 tons, that's not much. But the dinosaur eggs, which are not infrequently found, are much smaller.

The largest known dinosaur eggs come from large predatory dinosaurs and are approximately loaf-shaped and from sauropods, the giant dinosaurs. New finds from Argentina show that their eggs were round and had a content of no more than 4 liters; the maximum diameter was 25 cm.

A research group at the University of Bonn led by Dr. Martin Sander, who studies the life of giant dinosaurs, has found clutches of giant dinosaurs in northern Spain and southern France. The clutches, which were originally covered with earth, contain only about 6 to 8 eggs; with a total weight of less than 20 kg. Each clutch therefore represents a very small investment for a mother animal weighing perhaps 20 tons.

It can be assumed that the female giant dinosaurs - like all other animals - invested around five percent of their own weight in the reproductive process. Then there are two possible explanations for the findings: Either the dinosaur mothers carried out extremely energy-intensive brood care for the few expected hatchlings or they produced more than one clutch. The latter is more likely.

It can therefore be assumed that the females produced many clutches each year, which they dug into the ground at various favorable locations. This explains the discovery of the remains of around 400,000 eggs at one point in the southern Pyrenees: the female dinosaurs thought it was particularly suitable for laying eggs for several millennia.

Nevertheless: the too 'small' and too few eggs of the large dinosaurs are one of the many puzzles that still have to be solved in order to understand the way of life of the giant dinosaurs.

These and other questions of paleontology will be discussed at the 73rd annual conference of the Paleontological Society from September 29th to October 3rd in Mainz. According to the motto: 'Background to biodiversity: Endogenous and exogenous mechanisms of evolutionary development'.

PD Dr. P. Martin Sander
Institute of Paleontology
Nussallee 8, 53115 Bonn, Germany
Tel .: 0228/733105
Fax: 0228/733509
Email: [email protected]

Paleontological Society
The Chairman
Prof. Dr. Wighart of Koenigswald
Nussallee 8, 53115 Bonn, Germany
Tel .: +49 (228) 73 3104
Fax: +49 (228) 73 3509
Email: [email protected]

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