- The Paleontological Society
Protostegids are Cretaceous marine turtles. Fossil materials assignable to the family Protostegidae range from early Albian to Late Campanian in age and have been described from all continents except Antarctica (Hirayama, 1995). The group includes two gigantic forms, Archelon Wieland and Protostega Cope, that reached maximum carapace lengths in excess of 2 m and rank among the largest turtles that ever lived.
In this paper, we describe two specimens of Protostega gigas Cope housed in the Field Museum of Natural History (FMNH), Chicago, Illinois: FMNH P27452 and FMNH PR58. Both are from the Mooreville Chalk (Upper Santonian to Lower Campanian: Mancini et al., 1995) in Greene County, Alabama, and are noteworthy because they show tooth marks from at least one large shark. One of the specimens also exhibits five embedded teeth of the Late Cretaceous cretoxyrhinid shark Cretoxyrhina mantelli (Agassiz). This note constitutes the first report of protostegid turtles bitten by C. mantelli.
The specimen consists of disarticulated bones of a partial skeleton. Two bones that exhibit evidence for shark biting are considered here: a nearly complete left humerus (Figs. 1.1, 2.1; also illustrated in Zangerl, 1953, fig. 49) and a left hyoplastron (Figs. 1.3, 2.2).