BY DR. JOSE PALU-AY DACUDAO
THE GREATEST mass extinction in the planet’s history occurred around 252 million years ago, at the junction of the Permian Period (299 million to 252 million years ago) and the Triassic Period (251 million to 200 million years ago). The synapsid therapsids, from which mammals derive from and to which clade mammals belong to, were the dominant land creatures during the Permian. But shortly after the mass extinction event, sauropsid archosaurs (from which dinosaurs and crocodilians are derived from) took over (the so-called Triassic takeover). Perhaps, it was because of the advantages offered by the archosaurs’ urinary and respiratory systems mentioned above, but the case is unclear. In the latter part of the Triassic true dinosaurs began to dominate. Thus, dinosaurs dominated the medium to large animal niches of the Earth for most of the Mesozoic Era (251 to 66 million years ago). For that extended period of time, mammals (which also appeared in the latter part of the Triassic, derived from therapsid cynodonts) mostly remained the size of shrews and mice. Then non-avian dinosaurs became extinct 65 million years ago at the end of the Cretaceous Period (145 million to about 65 million years ago). (The two most popular theories are a bolide strike from outer space in Mexico or prolonged volcanism that formed the Deccan Traps flood basalts of India or both.) This despite the dinosaur’s’ more efficient respiratory and excretory systems compared to mammals. The mammals rapidly took over the niches occupied by dinosaurs. A popular theory is that the small burrowing mammals could resist catastrophic environmental changes better than large exposed dinosaurs that needed more food.
In my opinion the intelligence and adaptability that bigger brains with more numerous neurons confer to their owners was the more decisively important factor.
If dinosaurs had a cerebral cortex, they might be ruling the world until now.
Although they have been displaced by mammals in most terrestrial niches, the good news for dinosaur fans is that they are still around, and still successful. Today there more than 11,000 living species of avian dinosaurs, the birds, which is more than the 6,400 species of extant mammals. (It must be noted though that extant mammals are far more diverse than birds in morphology and the niches they occupy.)
Just today, I ate egg omelet. Gosh, I just ate the egg of a dinosaur!
Yes, birds are dinosaurs./PN
