Sauropterygia–> Eosauropterygia –> Eusauropterygia

The clade Eusauropterygia includes all sauropterygians except for the placodonts and the superfamily Pachypleurosauria. The genus Corosaurus was originally placed outside of Eosauropterygia but is now recognised as a pistosauroid within Eusauropterygia (Rieppel, 1998). The Eusauropterygia are characterised by a derived suite of characters including (Rieppel 1997, Sues 1986):

Elongation of the jaws and mandibular symphysis (large skull),

Strongly procumbent rostral dentition and paired maxillary fangs,

5 premaxillary teeth,

Small orbit (relative to skull length),

Dorsoventral depression of the skull,

Relative size increase in the upper temporal fenestrae,

Complex dual jaw adductor system,

Scapular proportionately small,

Five or six sacral vertebrae.