Error bars are ± two standard errors of the mean. (A) The Phanerozoic time series of mean geographic range in North America tabulated using Macrostrat. Breaks in the endemic data at the late Permian and late Jurassic indicate times for which there are no marine genera endemic to North America in the Paleobiology Database. The box shows the portion of the time scale expanded in the plot below. Points are plotted at the geologic time interval midpoints. (B) An expansion of the Cenozoic portion of the time series is presented in the plot above. (C) The Phanerozoic time series of mean geographic range in North America was tabulated using the simple convex hull method of calculating geographic range. (D) An expansion of the Cenozoic portion of the time series is presented in the plot above. (E) The Phanerozoic time series of mean geographic range in Europe was tabulated using the simple convex hull method of calculating geographic range. (F) An expansion of the Cenozoic portion of the time series is presented in the plot above. The Phanerozoic time scale abbreviations are as follows: Cm, Cambrian; O, Ordovician; S, Silurian; D, Devonian; C, Carboniferous; P, Permian; Tr, Triassic; J, Jurassic; K, Cretaceous; Pg, Paleogene; Ng, Neogene. The Cenozoic time scale abbreviations are as follows: Pal, Paleocene; Eo, Eocene; Olig, Oligocene; Mio, Miocene; Plio, Pliocene; P, Pleistocene.

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