Some 353 isolated skulls and partial to complete skeletons with known locations have been collected in ∼100 years from the 80 km2 of badlands in Dinosaur Provincial Park (DPP), Alberta, Canada. We wanted to estimate how many skeletons were lost to erosion before collection began and how many await discovery. Within the boundaries of DPP, a volume of rock 145 m thick between the surface of the down-cutting Red Deer River and the capping prairie was subdivided into 5 m thick slabs using digital elevation data with an average horizontal spatial resolution of 19 m and a vertical resolution of 1 m. The exposed surface area of each slab was calculated. Dinosaur fossil localities were determined with high-precision GPS surveys. The number of dinosaurs collected from the surface of a 5 m slab was divided by the product of the exposed area and an estimated erosional thickness of 80 cm to give a volume density of dinosaur fossils. Multiplying the volumes of rock lost from each layer by the dinosaur densities for each layer, the numbers of skeletons lost was determined. Estimates of the numbers of raisins in two loaves of raisin bread were made using a limited number of slices as a test of the method. Of the original volume of DPP, 6.58 km3 (60%) has eroded away, taking with it a mean number of 6310 hadrosaurs, 1640 ceratopsians, 1030 ankylosaurs, and 1600 theropods. The 5.02 km3 (40%) of rock remaining in the park can be expected to produce more dinosaur fossils of similar quality, with mean values of 6700 hadrosaurs, 1700 ceratopsians, 1010 ankylosaurs, and 1720 theropods. These estimates are minima as the estimation process excluded bone beds, the plethora of isolated bones littering the land surface of DPP, and the 100+ skulls and skeletons from the region that lack locality information.

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