Genus: Archaeonectrus Author: Novozhilov 1964 Taxon status: Classification: Plesiosauria → Pliosauroidea → Rhomaleosauridae Locality: UK → Dorset → Charmouth Age: Jurassic → Early Jurassic → Sinemurian Horizon (rock units): Jurassic → Lower Jurassic → Lias Group → Charmouth Mudstone Formation?
Etymology: Greek, arkhaios, 'ancient', Greek, nektris, 'swimmer': Ancient swimmer
Species: Archaeonectrus rostratus
Species: Archaeonectrus rostratus Species author: (Owen 1865) Species status: , , Age: Jurassic → Early Jurassic → Sinemurian Type horizon (rock units): Jurassic → Lower Jurassic → Lias Group → Charmouth Mudstone Formation? Type specimen: NHMUK PV OR 38525 Referred specimens: None
Species etymology: In reference to its elongate snout (rostrum)

The genus Archaeonectrus was proposed by Novozhilov (1964) for ‘Plesiosaurus’ rostratus, a species named by Owen (1865). By modern standards, Owen’s (1865) original description is rather inadequate. One notable characteristic of Archaeonectrus rostratus is the relatively small size of the limbs relative to its body. It has been classified as a pliosauroid, sometimes within the Rhomaleosauridae. Archaeonectrus rostratus is the type and only species of this genus.

Skeleton of Archaeonectrus. Lithograph from Owen (1865).
Archaeonectrus illustration (From Novozhilov 1964)
Archaeonectrus illustration. From Novozhilov (1964).