Evolution and Extinction of Dinosaurs

Abstract

In contrast to the view that mass extinction of dinosaurs was caused due to impact of a huge meteorite, the author contemplates
that to understand such crucial problem at first it is prerequisite to review the cause for the growth of small animals to larger
size. Geological records reveal that Permian and Carboniferous era were marked by extensive formation of coal deposits in
various parts of the globe which obviously implies that during that period widespread photosynthesis causing enrichment of
oxygen of the global atmosphere occurred. Growth of animals thus can be linked with favourable oxygen enriched environment
of the Triassic when plenty of food was readily available. Geological evidence further confirms that during the next K-T
boundary stage extensive volcanism took place in various parts of the globe. In consequence of such volcanic activity, oxygen
content of the global atmosphere must have been substantially reduced associated with rise in temperature that affected the
entire global environment. Therefore, selective extinction of large-sized animals that required higher amount of oxygen for
sustenance can be directly linked with depletion of oxygen during K-T boundary stage. On the other hand, the evidence shows
that the small animals that required comparatively lesser amount of life-sustaining oxygen could easily survive such ordeal.