plesiosaur
Aug. 21st, 2018 08:32 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
prettygoodwordplesiosaur (PLEE-see-uh-sawr) - n., any of various extinct marine reptiles (order Plesiosauria) having a broad flat body, four paddlelike flippers, a short tail, and sometimes a very long neck.
Their ancestors, who seem to have been most closely related to turtles, returned to the sea in the early Triassic; plesiosaurs developed from these in the late Triassic around 203 million years ago, and thrived after the Triassic-Jurassic extinction to the point that they displaced icthyosaurs as the apex marine reptiles. They lived until the Cretaceous extinction. Plesiosaurs had two general morphologies: a long-necked small-headed one, the classic plesiosaur shape, which were ambush predators, and a short-necked large-headed one often called pliosaur, which were apex predators. At one time, the plesiosaurs and pliosaurs were thought to be separate families, but turn out to be all mixed together -- separate morphs evolved multiple times. This picture has a plesiosaur above and an pliosaur below:
Thanks, WikiMedia!
The name plesiosaur was coined in 1821 from Greek roots plēsíos, close to + saûros, lizard, because they had a form closer to dinosaurs than icthyosaurs (cladistically they are as well, but they didn't know that back then).
---L.
Their ancestors, who seem to have been most closely related to turtles, returned to the sea in the early Triassic; plesiosaurs developed from these in the late Triassic around 203 million years ago, and thrived after the Triassic-Jurassic extinction to the point that they displaced icthyosaurs as the apex marine reptiles. They lived until the Cretaceous extinction. Plesiosaurs had two general morphologies: a long-necked small-headed one, the classic plesiosaur shape, which were ambush predators, and a short-necked large-headed one often called pliosaur, which were apex predators. At one time, the plesiosaurs and pliosaurs were thought to be separate families, but turn out to be all mixed together -- separate morphs evolved multiple times. This picture has a plesiosaur above and an pliosaur below:
Thanks, WikiMedia!
The name plesiosaur was coined in 1821 from Greek roots plēsíos, close to + saûros, lizard, because they had a form closer to dinosaurs than icthyosaurs (cladistically they are as well, but they didn't know that back then).
---L.
