Dinosaur eggs from the Cretaceous of the Gobi Desert.

NOTE ON TERATOLOGICAL DINOSAUR (?) EGGS
GRAZYNA MIERZEJEWSKA
ROMAN KOZLOWSKI INSTITUTE OF PALEOBIOLOGY, WARSZAWA
Acta Medica Polona 1977, 18, 4, 345-346

The eggs of reptiles and birds are found in fossil state very rarely. The Polish-Mongolian Paleontological Expeditions to the Gobi Desert have gathered from the Upper Creataceous the greatest in the world collection of fossil eggs. Some of the specimens belong to dinosaurs, others to turtles, crocodilians, lizards or birds. The present paper presents preliminary information on teratological dinosaur (?) eggs from this collection.

Material and methods. The studied material includes fragments of dinosaur (?) egg shells about 100 million years old. These shells were prepared for scanning electron microscope study using mainly methods described in detail by H.K. Erben (Biomineralisation 1, 1970). Moreover, the polarizing microscope was used. The studies were done at the M.Nencki Institute of Experimental Biology (Pol. Acad. Sci.) and Institute of Plant Culture and Acclimatization on JSM S-1 and Stereoscan 180 electron microscopes.

Results and discussion. Eggs of teratological, double or tripple shells (Fig. 1) have been discovered. The structure of these shells is rather different then the structure of "ovum in ovo" from the Cretaceous of Southern France studied by H.K. Erben. In the latter case there is a compact contact between the first and second egg shell. The teratological egg shells from the Gobi Desert do not cling to one another compactly. There no contact between the first shell mammilary zone and the second egg shell. An analogous situation is observed in eggs of tripple shells.

One of the egg shells found in close association with embryos, exposes the teratological double structure (the first finding of complete embryos in fossil eggs). Further palaeohistological study may allow to determine a degree of ossification of the embryo and clarify wheter the mentioned double shell had made impossible the hatching of young individual. The teratological thickening of the shell, as well as the obstruction of shell pores (Fig. 2: normal shell pore), seems to have been genetically controlled in late Cretaceous dinosaurs. Studies on ultrastructure and palaeobiochemistry of egg shells and their organic matrix may also clarify many problems of taxonomic position of fossil egg shells from the Gobi desert and the bases of their teratology. This problem is very important for explanation of dinosaur extinction.

An elongated dinosaur egg
from the Cretaceous of the Gobi Desert.
Nearly 20 cm long.
Collection of Roman Kozlowski Institute of Paleobiology.