Definition of "trionychid"

It is perhaps instructive to note that tropical riverine batagurids, although more similar to other river-dwelling lineages in reproductive patterns than to other semi-aquatic and terrestrial batagurids, still tend to have lower fecundities and bigger eggs relative to their body sizes than do the other groups (e.g., riverine emydids, trionychids, and podocnemids) (Moll & Moll, 1990).

2004, Don Moll, The Ecology, Exploitation and Conservation of River Turtles‎, page 46

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