DOI: 10.31038/GEMS.2025723

I would like to present here a substantially different view for the cause of extinction of dinosaurs for which, to start with, the cause of growth of the huge animals is vital to understand. The concept suggests that the Permian and Carboniferous era were marked by rich Gondwana coal deposits formed from glossopteris-rich forests of that era. These thick forests would cause extensive process of photosynthesis, thereby producing considerable amount of oxygen that would enrich the atmosphere. Hence it can be visualized that oxygen content of the atmosphere of Triassic period must have been very high compared to the earlier periods. In consequence it seems that the animals of the Triassic period roamed in an oxygen-rich environment where plenty of food was also available. The fossil records point out that animals of that period became huge in size, which can, therefore, reasonably be related to the oxygen-rich environment associated with availability of food of that period. However, during K-T boundary stage a contrasting situation prevailed when widespread volcanism occurred in various parts of the globe for which oxygen content of the atmosphere substantially reduced. This led large animals which required larger quantum of oxygen for sustenance to face selective extinction whereas smaller animals were not affected. Hence, it seems in the pertinent geological ages the following events took place (Table 1).

Table 1: Pertinent geological ages

Conclusion

I consider that cause of extinction of large sized animals of various types which also consist of birds, bipedal and quadrupedal animals of both herbivorous and carnivorous types, commonly termed as dinosaurs, was not due to impact of meteorites, but depletion of oxygen of the atmosphere. During the Triassic period oxygen content of the atmosphere was greatly enhanced owing to widespread photosynthesis of the glossopteris forests. In such a congenial oxygen-enriched environment with plenty of foods, the animals grew up to large size. However, due to the incidences of igneous activities that occurred during the Cretaceous period oxygen content of the atmosphere was significantly depleted when the large-sized animals that required more oxygen selectively faced extinction while the smaller animals remained unaffected.