• WordNet 3.6
    • n Plesiosauria any of the plesiosaurs
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Webster's Revised Unabridged Dictionary
    • n. pl Plesiosauria (Paleon) An extinct order of Mesozoic marine reptiles including the genera Plesiosaurus, and allied forms; -- called also Sauropterygia .
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Century Dictionary and Cyclopedia
    • plesiosauria An order of extinct marine Reptilia, having the limbs fitted for swimming, the body fish-like, the neck long, and the head quite small. The fore and hind limbs both constitute flippers or paddles like those of cetacean mammals, having numerous phalanges inclosed in a common integument like a fin. The pectoral arch is complete, with triradiate scapular and large coracoid and clavicular elements, and the pelvis is large, with separate ilium, ischium, and pubis. There is no sternum, nor are there any sternal ribs, but floating abdominal ribs are present. The skull has a fixed quadrate bone, one postorbital bar, and no free paroccipital; the vertebræ are amphicœlous, with neurocentral sutures, and only two of them compose a sacrum. The ribs are one-headed. The eyeball has no sclerotic ring of bones, and the teeth are socketed in a single row in both jaws. The order contains many genera of gigantic fish-like saurians from the Trias, Lias, and Chalk, whose affinities are with the chelonians, notwithstanding the wide difference in form. The order is also called Sauropterygia, but Plesiosauria is its prior and proper name. See cut under plesiosaurus.
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Webster's Revised Unabridged Dictionary
NL. See Plesiosaurus


In literature:

This, of course, is especially the case as regards the marine Ichthyosauria and Plesiosauria, of which such numbers of remains have been discovered.
"On the Genesis of Species" by St. George Mivart
Serpent dragons (Plesiosauria); 44.
"The History of Creation, Vol. II (of 2)" by Ernst Haeckel