FIGURE 1. Map of Potomac Formation outcrop belt in Maryland and surrounding states with the approximate location Dinosaur Park indicated by yellow star (map modified from Jud, 2015).
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FIGURE 2. Hybodont sharks from the Arundel Clay. 2.1 USNM 609336, 2.2 and 2.3 USNM 609325, and 2.7 USNM 521182 teeth and cephalic spine from Egertonodus basanus. 2.4 USNM 609350, 2.5 and 2.6 USNM 609349, teeth from Hybodus ensis. 2.8 and 2.9 USNM 521181 dorsal spines from Hybodontoidea indet.

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FIGURE 3. Fish material from the Arundel Clay. 3.1 USNM 521167, Lepidotes indet. jaw. 3.2 USNM 521169, Vidalamiinae tooth. 3.3 and 3.4 USNM 497787, amiiform vertebra in articular and ventral views. 3.5 and 3.6 USNM 497800, Holostei scale morphotype 1. 3.7 and 3.8 USNM 521146, Holostei scale morphotype 2. 3.9 and 3.10 USNM 521150, Holostei scale morphotype 3. 3.11 and 3.12 of USNM 497785, indeterminate teleost vertebra in ventral and dorsal views.

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FIGURE 4. Testudines and crocodilians from the Arundel Clay. 4.1, USNM 497784, Glyptops caelatus shell fragment. 4.2 and 4.3 USNM 609376, cf. Bernissartiidae tooth. 4.4 and 4.5 USNM 609383, 4.6 and 4.7 USNM 609428, 4.8 USNM 609362, cf. Goniopholididae teeth and osteoderms. 4.9 and 4.10 USNM 609370, cf. Pholidosauridae tooth.

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FIGURE 5. Saurischian dinosaur teeth from the Arundel Clay. 5.1 USNM 497732, Acrocanthosaurus sp.. 5.2 USNM 497743, Deinonychus sp.. 5.3 USNM 497748, aff. Richardoestesia. 5.4 USNM 497752, theropod indet.. 5.5-5.7 USNM 497763, Astrodon johnstoni.

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FIGURE 6. Ornithischian dinosaur teeth from the Arundel Clay. 6.1, 6.2, and 6.3 USNM 497783, basal neoceratopsian. 6.4 USNM 497777, Priconodon crassus. 6.5 USNM 497732, an indeterminate ankylosaur.

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FIGURE 7. Pie charts showing the faunal assemblages for mid-Cretaceous formations of North America; Arundel Fm. from this study, Antlers Fm. from the OMNH collections, Cloverly Fm. from Oreska et al. (2013) and the OMNH collections, and Cedar Mountain Formation from Goldberg (2000).