How many species of dinosaurs were there?

Answer 1

There seem to be a lot of different estimates.

"According to dinosaur diversity expert Steven Wang at Swarthmore College in Pennsylvania, US, there are approximately 550 widely accepted genera of dinosaurs (representing about 650 to 700 species), and new ones continue to be discovered. This figure is likely to be just a fraction of their true diversity, as many species may be absent from the fossil record."
http://www.newscientist.com/popuparticle.ns?id=in44

"Some think there may have been as few as about 1000 total genera. Others have estimated as many as 10,000 or more! Perhaps the best estimate lies in between -- approximately 3,000 dinosaur genera."
http://www.ccmr.cornell.edu/education/ask/index.html?quid=72

"The number of dinosaurs that have ever lived is estimated at 900-1200 genera."
http://www.pnas.org/cgi/content/abstract/87/19/7608

JMB

Answer 2

Nobody really knows the answer to this question. Estimates vary widely. We've seen figures between 250 and 550 or more (one research estimated a whopping 500,000 species). The numbers will continue to fluctuate. Many of these "different species" were actually assigned separate names based on scanty fossil evidence, sometimes only a tooth or vertebra. Dinosaur fossils are often expensive to excavate and collect. So, relatively few remains have actually been obtained by museums and paleontologists.

We haven't found any current estimates, but by the end of 1981 (according to an article in the Scientific American), there was only a total of about 5,000 fragments of dinosaur skeletons. [1]

Answer 3

we don't know but some paleontologists estimate that at least three fourths of all species remain to be discovered.