Rediscovery of the holotype of the extinct cephalopod Baculites ovatus Say, 1820 after nearly two centuries

ABSTRACT. Thomas Say (1787–1834) based his description of the ammonite species Baculites ovata (= B. ovatus) on a single specimen in the collection of his childhood friend, the Quaker naturalist Reuben Haines III (1786–1831). However, the specimen's whereabouts faded from memory after Haines and Say both died unexpectedly in the early 1830s. The holotype specimen has been missing for more than 180 years, and was thought to be lost or destroyed until 2017, when I relocated it at Haines's ancestral home (Wyck) in Philadelphia, Pennsylvania, where his collection was preserved by his descendants in its original wooden cabinet. Herein, I present the first photographic images, an illustration of its suture line, and quantitative measurements for use by systematic paleontologists.