Saturday, August 20, 2011

Dinosaurs: What Killed Them?

How and why dinosaurs went extinct has been debated for a long time.  Most paleontologists have settled on the asteroid impact theory.  Because of the huge disruption that this space object made, the earth’s climate changed.  Massive forest fires and dust clouds cooled the planet, causing everything larger than a crocodile to die off.  Moreover the asteroid left a layer of iridium, a rare element from space, which covered the extinction boundary.

However, there are a few who claim that the dinosaurs were under stress already.  The asteroid only hastened the demise of this weakened group of animals.  Fossil records show that fewer types of dinosaurs were living at the time of the asteroid’s impact.  Furthermore, the ecological niches formed by the new flowering plants were not being exploited by dinosaurs.

Moreover, one group of paleontologists analyzed a general pattern of dinosaur evolution.  As a rule, dinosaurs did not diversity to fill various specialized niches.  What brought these animals to prominence was the Triassic-Jurassic Extinction Event.  Dinosaurs took the role of disaster taxa and proliferated, crowding out other taxa.

Another theory that scientists often present is extensive volcanic activity.  As India separated from Madagascar, volcanoes in India became extremely active.  Forming the massive Deccan Traps in India, these volcanoes spewed forth dust and sulfuric ash that poisoned the air and water.  This could have placed extreme stress on the dinosaurs by destroying their environment.

Another reason for the demise of the dinosaurs could be disease.  According to this theory, insects rapidly expanded to fill the niche presented by the new flowering plants.  Many of these insects carry diseases that were fatal to some dinosaurs.  Therefore diseases further weakened the dinosaurs.

The problem with many of these theories is that they fail to explain the demise of the marine and flying reptiles that occurred at the same time.  Also frogs and salamanders, known to be sensitive to toxic changes, managed to survive to the present day.  In addition, these theories seem to focus on the larger dinosaurs, and neglect what may have happened to the smaller ones.  Some of the smaller ones may have evolved into birds, which exist today.

The evidence in the fossil record is that the climate became colder, and the sea level dropped.  Ice caps formed in Antarctica. What caused this dramatic change seems to be the impact of the asteroid.  This asteroid strike raised enough dust and ash to bring about such a sudden change.  The result was the extinction of so many different kinds of animals.

Works Used:
Haines, Tim and Paul Chambers, “The Complete Guide to Prehistoric Life”, Firefly: Ontario, 2006.

Little, Richard, “Dinosaurs, Dunes, and Drifting Continents: the Geohistory of the Connecticut Valley”, self-published, Hartford, CT, 1986.

Scott, Michon, “Strange Science: The Rocky Road to Modern Paleontology and Biology”, 2011,,

Strauss, Bob, “Dinosaurs at”,, 2011,,

Various, “Prehistoric Life”, Dorling Kindersley: New York, 2009.

----, “What Killed the Dinosaurs”,, 2001,,

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