The Age of Reptiles ended because it had gone on long enough and it was all a mistake in the first place.
- Will Cuppy, How To
Become Extinct (1941)
I haven't read the book nor did I
hear about it until a week ago when I was surfing away on the World Wide Web
and chanced upon this quote from the book (I have to admit - the title is quite
eye-catching and I might be found reading it in the near future). I also do not
know the context in which this sentence is used within the book but I do
disagree with Mr. Cuppy's view here. For those less proficient in the Geologic
Time Scale, the Age of Reptiles was the Mesozoic era which started around 251
million years ago and ended nearly 65 million years ago. It is so called
because of the ridiculous dominance that the reptiles enjoyed over Earth,
especially the most popular among their family, the dinosaurs for the whole
duration of this era. These 'terrible lizards' (the literal meaning of dinosaur
in Greek) were the undisputed rulers of this planet for nearly 186 million
years. In comparison, we, Homo
sapiens, have been around for
just about 2,50,000 years out of which nearly half that time was spent solely
in the continent of Africa. I don't think we have earned the right. So, what
unique characteristics did the dinosaurs possess that helped them lord over the
lands for that amount of time? How were they different from their
contemporaries?
The Age of Reptiles, a 34 m mural depicting the period when reptiles were the dominant creatures on the earth, painted by Rudolph Franz Zallinger.(for full image: http://donglutsdinosaurs.com/wp-content/uploads/2012/02/Age-of-Reptiles-1000x302.jpg |
Numerous theories have been put
forth to explain this long reign of the dinosaurs. Ranging from
post-apocalyptic survivors to sheer luck, these theories cover almost all the
ways that they could have adopted to pull through some hard times. I wish I had
the time to discuss all of them.
The first dinosaurs appear in the fossil record some
time after the largest mass extinction in the Earth’s history at the end of the
Permian period. Known as the ‘Great Dying’, the Permian extinction event
decimated most of the existing reptile and amphibian groups. A large part of
the ecosystems and various kinds of ecological niches were up for grabs after
being vacated in such dramatic fashion. According to studies, the dinosaurs
formed a part of the group that led the recovery of these ecosystems in the
Triassic period that followed. However, in the early years of their evolution,
dinosaurs were one of subordinate groups and largely remained under the radar
as other reptile groups diversified. This would remain unchanged throughout the
Triassic and, as luck would have it, another major mass extinction event
occurred, this time at the boundary of the Triassic and Jurassic period. This
event is attributed to have accelerated the rise of the dinosaurs (who
survived) to the top by getting rid of the competition.
It was not just mass extinction events that helped the
dinosaurs on their way. Evolution played its role too. A variety of unique
features are shared by all dinosaurs that set them apart from any other
vertebrates and more importantly, the other reptile groups. Anatomically, there
were two changes that are of particular importance, providing an important
evolutionary advantage to early predatory dinosaurs. Unlike their
contemporaries and predecessors, the dinosaurs had an upright stance. This was
aided by strong knee and ankle joints which were firmly attached to the shin
bones with a hinge joint at both ends. This vastly improved their speed and
agility and gave them that extra edge over other slower organisms.
Dinosaurs were odd physiologically as well. You see, most
reptiles today are ectotherms i.e. they are cold blooded and need external
sources to maintain their body temperature. However, our illustrious giant
lizards were allegedly endotherms (warm blooded) and there’s proof. Their
growth rate was phenomenal when compared to their reptilian brethren and it is
comparable to living warm blooded animals. Their bone textures (irregular as in
mammals as compared to the neat parallel rows of typical reptiles) and oxygen
isotope ratios of extremities (16O and 18O ratios depend
on temperature) also point to the same conclusion – dinosaurs maintained their
own body temperature.
It is truly remarkable that this group of animals, nearly
non-existent at the start of the Triassic, could go on to leave such an
everlasting impact on the planet’s history so much so that young human beings
would be fascinated when a movie featuring them would be made nearly 65 million
years after their demise. We may never learn the reason behind this dominance
but one thing is for sure – it was not a mistake.
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