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Cope's suppressed plate of the Elasmasaurus Platyurus, 1868.
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Skeletal sketch of the Anterior portion of the "head-on-the-wrong-end" version of Elasmosaurus platyurus published initially by Cope (1869, Pl. II, Fig. 1). The ten dorsal vertebrae shown in black approximate those noted by Cope to be missing from the type specimen. Note that Cope did not include the hind paddles in this figure in part due to his erroneous belief that Elasmosaurus was propelled by its extremely long "tail".

Credit: Courtesy of The Academy of Natural Sciences, Ewell Sale Stewart Library

After E.D. Cope proudly unveiled a new plesiosaur, Elasmosaurus, his nemesis O.C. Marsh pointed out that Cope had mounted the skull on the wrong end. Elasmosaurus had a long, skinny neck, not a long, whiplike tail. The short-necked, long-tailed version is illustrated here. Standing in a kangaroo-like stance is Cope's first dinosaur discovery, Laelaps. The dinosaur didn't likely support itself on its tail, but the articulation is pretty accurate. Unfortunately for Cope, the name didn't stick; it had already been used to name a spider. Again, Marsh had the last laugh; he named the dinosaur Dryptosaurus in 1877

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