Endennasaurus acutirostris (Renesto 1992) Late Triassic ~210 mya, ~ is a derived thalattosauriform derived from Askeptosaurus and a sister to Thalattosaurus and Clarazia.
Distinct from Askeptosaurus, the skull of Endennasaurus was longer and toothless. The rostrum and mandible both tapered to a sharp point. The upper temporal fenestra were closed. The posterior process of the jugal was longer and more robust. The dentary rose to a broad, high coronoid process.
The cervicals were longer. The torso was shorter, low, wide and box-like, according to the ribs. The first few caudals had high neural spines, which raised the base of the tail.
The scapula was disc-like, like a coracoid. The coracoid was twice the size and elongated like a sternum. The humerus was much longer. Metacarpals 2-4 were aligned with 1 and 5 shorter. Finger 4 was reduced and finger 5 was further reduced.
The pelvis was larger as was the hind limb. Metatarsal V was hooked. Pedal digit 4 was longer and digit 5 was shorter.
A family tree of the Enaliosauria is here. A more complete tree of the Reptilia is here. The wide variety displayed by thalattosauriforms hints at a wider variety and several missing links yet to be discovered.