Atlantochelys mortoni, from the Late Cretaceous of Monmouth County, New Jersey, is among the largest ever marine turtles. For over a century and a half, it was known only from the proximal half of a humerus, until the corresponding distal half of the same bone was discovered a decade ago. Its authorship is typically attributed to Agassiz, 1849, but as Agassiz never formally published his findings, the correct authorship is Leidy, 1865. Protostega neptunia Cope, 1871 is an objective junior synonym.