Plesiosaur Vertebra | Fertebra Plesiosor

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Ymlusgiaid cigysol morol oedd Plesiosoriaid. Roedd rhywogaethau lu ohonynt, gan gynnwys Elasmosawrws, y mwyaf. Ymddangosodd Plesiosoriaid ar ddechrau’r Cyfnod Jwrasig, a buont yn ffynnu hyd nes Difodiant y Cyfnod Trydyddol Cretasig , pan wnaethon nhw ddiflannu’n llwyr. Roedden nhw’n hwylio’n araf o dan wyneb y dŵr, ac yn defnyddio eu gwddf hir hyblyg i symud eu pen er mwyn dal amonitau neu bysgod anwyliadwrus. Plesiosaurs were carnivorous marine reptiles. There were many species of plesiosaurs, including Elasmosaurus, the largest. Plesiosaurs appeared at the start of the Jurassic Period and thrived until the Cretaceous-Tertiary Mass extinction, when they became extinct. They cruised slowly below the surface of the water, using their long flexible neck to move their head into position to snap up unwary fish or ammonites.