Definition of "protostegid"

Loss of scutes (and corresponding loss of sucli[sic] on the underlying shell plates) is widely regarded as a derived condition that has occurred independently in trionychids, advanced carettochelyids (Carettochelyidae), and derived sea turtles such as dermochelyids and protostegids (e.g., Meylan 1988; Hirayama and Chitoku 1996).

2012, Donald B. Brinkman, editor, Morphology and Evolution of Turtles