Protostega

Protostega ('first roof') is an extinct genus of sea turtle containing a single species, Protostega gigas. The species lasted from the Coniacian to the Campanian stages of the Late Cretaceous. Its fossil remains have been found in the Smoky Hill Chalk formation of western Kansas (Hesperornis zone, dated to 83.5 million years ago), time-equivalent beds of the Mooreville Chalk Formation of Alabama and Campanian beds of the Rybushka Formation (Saratov Oblast, Russia). It is also known from rocks in Canada, with these sediments dating to the middle Campanian due to them being found in the Pembina member. Fossil specimens of this species were first collected in 1871, and named by Edward Drinker Cope in 1872. With a total length of , it is the second-largest sea turtle that ever lived, second only to the giant Archelon, and one of the three largest turtles of all time alongside Archelon and Gigantatypus. thumb|left|Protostega skeletal reconstruction in the Rocky Mountain Dinosaur Resource Center, Woodland Park, Colorado

== Discovery and history == The first known Protostega specimen (YPM 1408) was collected on July 4 by the 1871 Yale College Scientific Expedition, close to Fort Wallace and about 5 months before Cope arrived in Kansas. However, the fossil that they found was never described or named. It was not named until 1872, when E. D. Cope found and collected the first identified specimen of Protostega gigas in the Kansas chalk in 1871. A variety of bones were found in yellow Cretaceous chalk from a bluff near Butte Creek.