Placodontia

Placodonts ("tablet teeth") are an extinct order of marine reptiles that lived during the Triassic period, becoming extinct at the end of the period. They were part of Sauropterygia, the group that includes plesiosaurs. Placodonts were generally between in length, with some of the largest measuring long.

Henodus (from , 'one' and , 'tooth') is an extinct placodont of the Late Triassic period during the early Carnian age. Fossils of Henodus chelyops were found in the Estherienschichten Member of the Grabfeld Formation, near Tübingen, Germany and Loulé, Portugal. It was around in length. The single species within the genus is H. chelyops. Henodus is the only placodont thus far found in non-marine deposits, suggesting it may have lived in brackish or freshwater lagoons.

Placodus (from , "a plate" and , "tooth") is an extinct genus of marine reptiles belonging to the order Placodontia, which swam in the shallow seas of the middle Triassic period (). Fossils of Placodus have been found in Central Europe (Germany, France, Poland) and China.

Psephoderma (meaning "pebbly skin", from the Ancient Greek psepho (ψῆφος), "pebbly", and derma (δέρμα), "skin") is a genus of placodonts very similar to the related genera Placochelys and Cyamodus. Psephoderma had a flattened skull and a narrow, straight rostrum, much narrower than that of its relatives. Inside this skull, embedded in the jaws, were rounded teeth specialized for crushing the shellfish it ate. Unlike henodontid placodonts, Psephoderma's carapace was divided into two pieces, one on the shoulders and back, and another on the ventral end. Psephoderma grew to long, larger than many

Placochelys (from , "plate" and , "tortoise") is an extinct genus of placodont reptiles erected by Otto Jaekel in 1902.

Cyamodus (pron.: SIE-ah-MO-dus) is a genus of placodonts known from several species described from Middle-Late Triassic of Europe and China. The genus was described by Christian Erich Hermann von Meyer in 1863, based on specimens found in Germany. Like some other placodonts, Cyamodus has an armoured carapace composed of irregular hexagonal plates, with the mouth containing a small number of large, rounded teeth that were likely involved in crushing hard shelled organisms (durophagy).

Paraplacodus broilii is an extinct placodont sauropterygian from the Middle Triassic epoch, from the Anisian until Ladinian stages. The fossils were uncovered in Northern Italy and the species was named in 1931 by Bernhard Peyer. Paraplacodus means "Almost Placodus", in reference to its similarity to Placodus. thumb|left|Restoration thumb|left|Paraplacodus broilii fossil

Palatodonta is an extinct genus of neodiapsid reptile known from the early Middle Triassic (early Anisian stage) of the Netherlands. It was initially described in 2013 as a basal placodontiform closely related to a group of marine reptiles called placodonts, characterized by their crushing teeth and shell-like body armor. Under this interpretation, Palatodonta is transitional between placodonts and less specialized reptiles. Like placodonts, it has a row of large teeth on its palate, but while these teeth are thick and blunt in placodonts, Palatodonta has palatal teeth that are thin and pointe

Cyamodontidae is an extinct family of superficially turtle-like placodonts belonging to the superfamily Cyamodontoidea. Fossils have been found in Germany and Italy. It is named after Cyamodus, the namesake of the family.

Henodontidae is an extinct family of superficially turtle-like placodonts belonging to the superfamily Cyamodontoidea. Fossils have been found in Germany and Spain.

Placochelyidae is an extinct family of placodonts belonging to the superfamily Cyamodontoidea.

Placodontiformes is an extinct clade of sauropterygian marine reptiles that includes placodonts and the non-placodont Palatodonta. It was erected in 2013 with the description of Palatodonta. Placodontiformes is the most basal clade of Sauropterygia and the sister group of Eosauropterygia, which includes all other sauropterygians.

Parahenodus (meaning "near Henodus", with Henodus meaning "single tooth") is an extinct genus of henodontid placodont only known from a skull, discovered between 2008 and 2015 and described in 2018. It lived during the Late Triassic (Carnian–Norian). The skull, named and described as Parahenodus atancensis, was discovered in Keuper Facies of the Castilian Branche of the Iberian Range in the reservoir of El Atance (Sigüenza, Spain). It was the sister taxon to Henodus.

Pararcus is an extinct genus of placodont marine reptile from the Middle Triassic of the Netherlands. The genus is monotypic and the type species is Pararcus diepenbroeki. Pararcus is known from a holotype skeleton about long from the Lower Muschelkalk of Winterswijk.