![]() This hypothesis was presented to scientists in 1996 (March and Bishop, 1996) and resulted in the discovery of the world's first documented fossilized sea turtles nest in the Cretaceous Fox Hills Sandstone near Limon, Colorado in 1997 (Bishop et al., 1997).Ī cast of the giant Cretaceous sea turtle, Archelon, from southwestern South Dakota collected in 1976 Original is at the National Natural History Museum in Vienna, Austria. However, the duration and intensity of sea turtle nesting during the last 105 million years assures that when and where marine shoreline sediments are preserved, there could be sedimentary structures (markings in the rock) made by nesting sea turtles. The beach is a very ephemeral environment in the geologic record, seldom preserved in the rock record. Notochelone), from South Australia (Kear, 2006) indicating that that turtle's diet consisted primarily of the Cretaceous bivalve Inoceramus.īecause sea turtles nest on sandy beaches, they leave behind evidence of this activity as a suite of traces or markings on the beach, consisting of crawlways and nests. Gastric residues and coprolites (fossil dung) have been found preserved with several small Albian sea turtles, protostegid turtles ( cf. Scavengers often leave evidence of their activity as bitten or broken bones. Because dead sea turtles tend to bloat and float after death and are a ready source of food for scavenging animals, their carcasses are torn apart and decompose allowing bones to fall off as they drift and are rocked by the surge of waves. Throughout their 100 million year history sea turtles have adapted to changing conditions as seas rose and fell against the continents, continents drifted apart and collided, and glaciers formed and melted.įossil evidence of sea turtles includes hard parts preserved as fossils, body fossils, and evidence of sea turtle activities left as sedimentary structures in the sediment, trace fossils.īody fossils of sea turtles consist of a few complete specimens and many more partial specimens consisting of disassociated skeletal elements. Sea turtles have been present in the Earth’s oceans at least since the Early Cretaceous (~105 mybp) (Hirayama, 1998 Kear and Lee, 2006), and possibly since the Late Jurassic Period when they lived at the same time as the dinosaurs. (Courtesy of Triebold Paleontology, Inc.) A cast of a juvenile Cretaceous sea turtle, Toxochelys, whose carapace, usually from 2 to 4 feet long is only about 24 cm (9.5 inches) long.
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