To paraphrase Shakespeare: there are more dinosaurs in earth and rock than dreamt of by modern paleontology. Revising an earlier estimate based on discoveries to date, anatomist Peter Dodson of the University of Pennsylvania and statistician Steve Wang of Swarthmore College predict that 71 percent of dinosaur genera--the organizational grouping into which individual species fall--still remain to be discovered. "It's a safe bet that a child born today could expect a very fruitful career in dinosaur paleontology," Dodson says.
Over the course of the last decade, the pace of dinosaur genera discovery nearly tripled as new fossil beds and researchers entered the field. "Since 1990, an average of 14.8 genera have been described annually, compared with 5.8 genera annually between 1970 and 1989 and 1.1 genera annually between 1824 and 1969," the researchers write in the paper presenting the finding, published online yesterday in Proceedings of the National Academy of Sciences. Dodson and Wang plugged those numbers into a statistical method known as an abundance-based coverage estimator, which has been used to estimate successfully the diversity of other animals. Their calculation reveals that dinos should have 1,844 genera--up from 1,200 genera that Dodson estimated in 1990. Only 527 genera have been discovered through May this year.
This statistical method relies on numbers of rare genera--those with fewer than 10 species extant as culled from the literature by the researchers--to estimate the total relative abundance of all genera. The numbers also seem to show that diversity was not declining as dinosaurs approached their inevitable end, instead it remained relatively stable as eons passed. And extrapolating forward, the researchers predict that we are entering a golden age of dinosaur genera, with 75 percent to be found over the next century or so.
Of course, given that dinosaur discovery relies on dinosaurs having died in areas conducive to fossilization, this estimate may prove to be simply the minimum number of genera awaiting uncovering, the researchers note. And Dodson had to revise his previous estimate upwards by roughly 50 percent. "I would never suggest that this prediction, however statistically sound, is the final word on dinosaur diversity," he says. "This is the best estimate we can make with the data available."