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Most dinosaurs still unaccounted for, study finds

Sept. 5, 2006
Courtesy University of Pennsylvania
and World Science staff

The gold­en age of di­no­saur dis­cov­ery is yet to come, two re­searchers say in a study that sug­gests most types of di­no­saurs are still un­dis­cov­ered.

Di­no­saur tracks on the banks of the Pur­ga­toire Riv­er in south­east­ern Col­o­rad­o. (Cour­te­sy U.S. Dept. of Ag­ri­cul­ture)
The sci­en­tists used a sta­t­is­ti­cal meth­od to es­t­i­mate the to­tal num­ber of di­no­saur ge­n­er­a—­tax­o­no­mic groups each con­tain­ing one or more spe­cies—based on finds to date. 

Their re­sult: 71 pe­r­cent of di­no­saur gen­er­a have yet to be un­earthed, not count­ing di­no­saurs that may be un­dis­cov­er­able be­cause they did­n’t fos­sil­ize.

Pe­ter Dod­son of the Uni­ver­si­ty of Penn­syl­va­nia in Phil­a­del­phia and Steve C. Wang of Swarth­more Col­lege in Swarth­more, Penn. de­tailed the find­ings in this week’s ad­vance on­line is­sue of the re­search jour­nal Pro­ceed­ings of the Na­tion­al Acad­e­my of Sci­ences.

The re­searchers al­so of­fered ev­i­dence that di­no­saur po­p­u­la­tions were sta­ble short­ly be­fore their ex­tinc­tion 65 mil­lion years ago. 

Dod­son pro­poses that 1,850 gen­er­a will even­tu­al­ly be dis­cov­ered, in to­tal. Since di­no­saur re­search be­gan in ear­nest in the 19th cen­tu­ry, on­ly 527 gen­er­a have so far been found, al­though that num­ber is ris­ing at the rate of 10 to 20 per year. 

“It’s a safe bet that a child born to­day could ex­pect a very fruit­ful ca­reer in di­no­saur pa­le­on­tol­o­gy,” said Dod­son. But “the child’s grand­chil­dren won’t be so for­tu­nate, as new dis­cov­er­ies will like­ly de­cline sharp­ly in the ear­ly 22nd cen­tu­ry.” 

The re­searchers pre­dicted that 75 per­cent of dis­cov­er­a­ble gen­er­a will be found with­in a century and 90 per­cent with­in the next 140 years. “The 1990s saw an 85% in­crease in the num­ber of new fos­sil dis­cov­er­ies,” Dod­son said. 

The di­ver­si­ty of di­no­saur ex­plor­ers is al­so on the rise, he added.

His­tor­i­cal­ly, Dod­son con­tends, di­no­saur dis­cov­ery was large­ly in the hands of Brit­ish, Ca­na­di­an and Amer­i­can re­searchers. But in re­cent decades the dis­cov­ery of new fos­sil beds, es­pe­cial­ly in Chi­na and Mon­go­li­a and South Amer­i­ca, has opened the field to man­y re­searchers from those coun­tries. 

Dod­son and Wang’s es­ti­mates for to­tal di­no­saur di­ver­si­ty take in­to ac­count the num­ber of di­no­saurs al­read­y found, the rate of dis­cov­ery and po­ten­tial rich­ness of the fos­sil lo­ca­tions that can be rea­son­a­bly ex­plored. 

It’s un­known wheth­er the calculation of dis­cov­er­a­ble gen­er­a mir­rors the ac­tu­al di­ver­si­ty of di­no­saurs that lived, the pair said, since it’s es­ti­mated that near­ly half of di­no­saur gen­era left no fos­sil ev­i­dence.

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The golden age of dinosaur discovery is still to come, two researchers say in a study that suggests most types of dinosaurs are yet undiscovered. The scientists used a statistical method to estimate the total number of dinosaur genera—taxonomic groups each containing one or more species—based on finds so far. Their result: 71 percent of dinosaur genera have yet to be discovered, without counting dinosaurs that are undiscoverable because they didn’t fossilize. Peter Dodson at the University of Pennsylvania in Philadelphia and Steve C. Wang of Swarthmore College in Swarthmore, Penn. detail the findings in this week’s advance online issue of the journal Proceedings of the National Academy of Sciences. The researchers also offered evidence that dinosaur populations were stable shortly before their extinction 65 million years ago. Dodson proposes that 1,850 genera will eventually be discovered, in total. Since the dinosaur research began in earnest in the 19th century, only 527 genera have so far been found, although that number is rising at the rate of 10 to 20 per year. “It’s a safe bet that a child born today could expect a very fruitful career in dinosaur paleontology,” said Dodson. But unfortunately, “the child’s grandchildren won’t be so fortunate, as new discoveries will likely decline sharply in the early 22nd century.” The researchers predicted that 75% of discoverable genera will be found within 60-100 years and 90% within the next 140 years. “The 1990s saw an 85% increase in the number of new fossil discoveries,” Dodson said. The diversity of dinosaur explorers is also on the rise, he added. Historically, Dodson contends, dinosaur discovery was largely in the hands of British, Canadian and American researchers. But in recent decades the discovery of new fossil beds, especially in China and Mongolia and South America, has opened the field to many researchers from those countries. Dodson and Wang’s estimates for total dinosaur diversity take into account the number of dinosaurs already found, the rate of discovery and potential richness of the fossil locations that can be reasonably explored. It’s unknown whether the estimates of discoverable genera mirror the actual diversity of dinosaurs that lived, the pair said, since it’s estimated that nearly half of all dinosaur genera left no fossil evidence.