The holotype specimen (NHMUK PV R 1336) was first and last described by Owen, 1840. ‘Plesiosaurus’ macrocephalus is probably a juvenile rhomaleosaurid, and certainly doesn’t belong to the genus Plesiosaurus. However, pending revision of the taxon and referral to a different or other existing genus, it is still named ‘Plesiosaurus‘, following Owen.
Early Jurassic, Sinemurian
Lyme Regis, Dorset, UK
Black Ven Marl Formation, Lower Lias.
NHMUK PV R 1336