Bone Dry

Will we ever run out of dinosaur bones?

A Tyrannosaurus rex museum display

The BBC reported yesterday that paleontologists in Australia have discovered a new species of dinosaur—a large, plant-eating sauropod nicknamed Zac. This follows a July discovery of three new species in the same part of northern Australia. It seems as if paleontologists are always stumbling across new skeletal remains, but how long can this last? Will we ever run out of dinosaur fossils?

Not for a long, long time. There are currently about 3,000 so-called “full” dinosaur specimens—complete or near-complete skeletons or just a complete or near-complete skull—in museums around the United States. Scientists estimate that there are at least triple this number as yet uncollected around the globe. It’s hard to say how long it will take to track these down. But currently we’re discovering new full specimens at a rate of about 14 per year. If we continue at that pace, it’s safe to say we won’t run out soon. (This rate is historically high—between 1970 and 1990, the rate was only six per year.) Pinning down the exact number of all uncollected fossils—not just complete specimens but bits and pieces like individual teeth or stray tail bones—is nearly impossible, but the figure is certainly in the millions.

Paleontologists have a far more precise idea of how many more dinosaur types or “genera” are left to discover. (Scientists use the term genera—the plural for genus—instead of species because most dinosaur types are represented by a single species; they’re “monospecific.” An exception is the Tyrannosaurus rex, a species of the genus Tyrannosaurus.) Using a statistical technique known as the abundance-based coverage estimator, scientists estimate that in the 165-million-year period that dinosaurs roamed the Earth, there were some 1,844 different genera, from carnivorous dinosaurs like the Velociraptor to herbivores like the Stegosaurus. Since humans started searching for dinosaur bones in 1824, it’s estimated that we’ve found remnants from 29 percent of these types, mostly in the last 20 years (a jump largely attributable to increased manpower and discoveries in Argentina and China). If we keep at the current pace of new discovery, it’s likely that we’ll hit something like “peak dinosaur,” with 50 percent of all dinosaur genera discovered, by 2037. Within the next 100 to 140 years, we will have found 90 percent.

Not all remaining dinosaur bones are actually worth collecting. For paleontologists, discovering new species is the first priority, followed closely by digging up complete or near-complete fossilized skeletons. But fragments of common dinosaurs aren’t particularly important for scientific research. So if a paleontologist stumbles upon the bones of, say, the hadrosaur Maiasaura (perhaps the most common dinosaur fossil), chances are she’ll move along without picking up the bones for closer study.

Bonus Explainer: Where’s the best place to go looking for dinosaur bones?

The United States, China, and Argentina have especially numerous fossil deposits, followed by Canada, England, and Mongolia. (China and Argentina have proved especially fertile as of late. Since 1990, there has been a 132 percent and 165 percent increase in genera discovery in these two countries, respectively.) These six countries account for 75 percent of the world’s dinosaur finds. Australia, Europe, and Africa are less fertile.

The top six are ripe for dinosaur discoveries because they once had interior waterways—essential for the fossilization process—and continue to have rock and sediment from the time when dinosaurs were around (a period called the Mesozoic Era). Good locations also tend to be places that are dry now—the Gobi desert; rock formations in Alberta, Canada—because researchers don’t have to dig up trees or move buildings to access possible sites. Places that are covered with vegetation may have a ton of dinosaur fossils, but getting at them is difficult. Clear away some of that vegetation, though, and the fossil landscape could change radically. Some claim that if England were a desert, it would quickly become the best dinosaur-hunting terrain in the world.

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Explainer thanks Peter Dodson of the University of Pennsylvania, Thomas Lehman of Texas Tech University, and Steve C. Wang of Swarthmore College.