page_title: Protostegidae
section_title: Anatomy
hierarchical_section_title: Protostegidae / Anatomy
caption_attribution_description: English: Protostega gigas - giant sea turtle from Late Cretaceous of Kansas Русский: Protostega gigas - гигантская морская черепаха из позднего мела Канзаса
context_page_description: Protostegidae is a family of extinct marine turtles that lived during the Cretaceous period. The family includes some of the largest sea turtles that ever existed. The largest, Archelon, had a head one metre long. Like most sea turtles, they had flattened bodies and flippers for front appendages; protostegids had minimal shells like leatherback turtles of modern times.
context_section_description: As some of the first marine turtles, the protostegids set the general body plan for future species of sea turtles. They had a generally depressed turtle body plan, complete with four limbs, a short tail, and a large head at the end of a relatively short neck. Like other sea turtles, they possessed oar-like front appendages especially evolved for swimming in the open ocean. Similar to the still-extant, possibly closely related Dermochelyidae, protostegids possessed extremely reduced carapaces. Some specimens had skeletal protrusions from their ribs almost wrapping around their bodies in place of a complete shell. Like modern sea turtles, protostegids had sharp beaks. One of the defining characteristics of the members of the family was their almost-disproportionately large heads. Specifically, some specimens of Archelon have been found with heads one metre (39 in) long. In addition, the members of the family had somewhat reduced plastrons, as well.
caption: Life restoration of Protostega gigas
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