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Umoonasaurus, crested plesiosaur from Australia

Apparently plesiosaurs could be crested too..

Benjamin P. Kear, Natalie I. Schroeder, and Michael S.Y. Lee. An archaic crested plesiosaur in opal from the Lower Cretaceous high-latitude deposits of Australia. Proceedings of the Royal Society B: Biology Letters. FirstCite Early Online Publishing.

Abstract: "_Umoonasaurus demoscyllus_ gen. et sp. nov. is a new small-bodied (approx. 2.5m) pliosauroid plesiosaur from the Lower Cretaceous (Aptian-Albian) of southern Australia. It is represented by several partial skeletons (one with a near complete skull is the most complete opalized vertebrate fossil yet known), and is unique in having large crests on the skull midline and above the orbits. _Umoonasaurus_ is surprisingly archaic despite its relatively late age (approx. 115Myr ago) - being simultaneously the most basal (primitive) and last surviving rhomaleosaurid. Notably, it lacks the ?pliosauromorph? features (large head, short neck, gigantism) typically characterizing many more derived Jurassic rhomaleosaurids; thus, reinforcing the suspected convergent evolution of the ?pliosauromorph? hypercarnivore body plan. _Umoonasaurus_ inhabited an Early Cretaceous high-latitude (approx. 70°S) inland seaway subject to seasonally near-freezing climatic conditions. This extreme environment supported a diverse range of plesiosaur taxa, suggesting that these marine reptiles might have possessed adaptations (e.g. heightened metabolic levels) to cope with cold-water temperatures. Indeed, survival of ancient endemic lineages such as _Umoonasaurus_ is a common phenomenon in Australian Cretaceous vertebrate assemblages and might have been facilitated by isolation in low-temperature high-latitude regions."