Extinction of the dinosaurs has come to symbolize the Cretaceous/Tertiary
mass extinction event. The impact theory, proposed by Alvarez others (1980),
renewed ethusiasm among scientists to find an a acceptable explanation
which satisifies all of the observed, and commonly contridicting evidence, associated
with the Cretaceous-Tertiary (K-T) boundary. This debate has been in progress for
18 yrs now, therefore, it can be seen that there is no clearcut answer.
To find out a brief history of the dinosaur; Click on the scroll
Limitations of evidence
Literature surrounding this topic produces many contradictions, with respect to;
absolute numbers of genera, their relative location in time, correlation of
different stratagraphic units and, thus, the overall nature of their extinction.
This problem is a result of the fact that the fossil record is very
It is important to view all the evidence presented here knowing that very
little is an absolute fact and that new theories develope from increased knowledge.
Continued field work and analysis will
eventually reveal the answers to one of the greatest debates science has
What is extinction and how is it measured ?;
Click on the spaceship and find out
Nature Of the K-T Extinction
Selective extinction did occur at the K-T boundary (Officer et al, 1987) as many
groups passed into the Tertiary unscathed.
Most biotic changes are related to short-term loss of primary productivity
(Coorough and Fastovsky, 1996). Animals in food chains who obtained there food
supply derived from photosynthesis suffered the greatest in the K-T extinction.
What is the evidence ? Follow Steggy back in time, to find out
Many clades reestablished themsevles after the K-T extinction
with little change in habitat, while others changed their lifestyles dramatically.
The species of flora (plants) and fauna (animals) which suffered the highested losses cannot be grouped together by
one single characteristic.
Detritus-feeders (i.e.scavengers of terrestrial and marine habitats), and
animals that could withstand prolonged periods of starvation e.g. 7 months,
preferentially survived whereas animals requiring green plants for food tended
to become extinct. However, many detrius-feeders did become extinct and many herbivores
What was the climate like? Fasten seat belts for a rocky ride
Why; The Causes of Dinosaur Extinction
Their demise was probably due to starvation through global collapse in the
producitivity of green plants (Sheenan and Fastovsky, 1992) caused by darkness
and acid rain (Hildebrand, 1993).
Perhaps a question of vunerability, dinosaurs were large creatures with small
populations, and it was their lack of ability to evolve and occupy new niches,
(Officer et al, 1987).
Perhaps it looked like this ?
Need to be able to link the sweep of biotic changes during the Masstrichtian
as a whole.
The era of the dinosaurs did not end because they were in decline but rather
they were changing into creature that were more diverse, more active and more
cerebral (brainy),therby more similar to modern birds and mammals. (Russell,
Hulbert & Archibald concluded in 1995, that there is not enough evidence to
argue for a sudden or gradual decline in dinosaur taxa at the end of the
Cretaceous. It must be iterated again, due to the lack of terrestrial K-T sequences, that there are no means to test this evidence to see if is a local or global phenomenon. A nest site in China, also of the magnetochron 29r, indicates the presence of dinosaurs but cannot provide any evidence with respect to; diversity and rate of decline.
Absence of mass mortality deposits at the K-T boundary constitues a weakness
in the asteroid impact theory for the extinction of the dinosaurs, Cutler and
Dinosaurs declined in diversity over the last several million years of the
Cretaceous, of which seems to accelerate towards the boundary, as depicted
in North America. However, there is no other evidence for the timing and
nature of this extinction in the rest of the world.
A major upset in the reproductive cycle of dinosaurs would result in a rapid
and dramatic decrease in population.
Glossary: will arrive soon!
Dinosaurs that are still alive:- Just a bit of fun
Thesaurus: Dictionary type book
Mumsaurus: Reason for being grounded after being caught doing something naughty!