Why was the plesiosaurus extinct?

Answer 1

Pterosaurs died out 65.5 million years ago during the same cataclysmic event that wiped out the non-avian dinosaurs and 75% of Earth's species. Most scientists believe that this event, the K-T Extinction, was the result of a 6 mile wide asteroid that smashed into the Yucatan Peninsula of Mexico, leaving a 100 mile wide crater. So much dust and ash was launched into the atmosphere that sunlight was blocked for months or years. This caused plants to die, and thus the animals that ate them also died. In turn, the carnivores starved, and that would have included the pterosaurs.

Answer2: That dinosaurs existed abundantly throughout the earth, in an ancient landscape long ago vanished, is obvious from the fossil record. But these amazing creatures, along with countless other animal and plant kinds, passed out of existence. As to just when these things took place, paleontologist D. A. Russell states: "Unfortunately, existing methods for measuring the duration of events that happened so long ago are relatively imprecise." Fossil record does not yield its secrets so easily and that no one on earth today really knows all the answers.

Listing some speculations as to what happened to them, Princeton scientist G. L. Jepson stated:

"Authors with varying competence have suggested that dinosaurs disappeared because the climate deteriorated . . . or that the diet did. . . . Other writers have put the blame on disease, parasites, . . . changes in the pressure or composition of the atmosphere, poison gases, volcanic dust, excessive oxygen from plants, meteorites, comets, gene pool drainage by little mammalian egg-eaters, . . . cosmic radiation, shift of Earth's rotational poles, floods, continental drift, . . . drainage of swamp and lake environments, sunspots."-The Riddle of the Dinosaur.

It is apparent from such speculation that scientists are not able, with any certainty, to answer the question: What happened to the dinosaurs?

Answer 2

The Plesiadapis became extinct during the Paleocene Thermal Maximum which was a period of intense global warming and significant habitat change. This extinction event was contemporary with the emergence of primate species in North America (it was a tropical rainforest at this time) -- roughly 55 mya.

Answer 3

To put it shortly, humans.

Megaladapis, also known as the koala lemur, was native to Madagascar. When humans began to colonise the island, they used slash and burn techniques to clear the jungles to build settlements. The Megaladapis looked very similar to a koala, but was in fact a lemur, which meant it lives in trees.

They shared some amazing similarities with koalas - their arms, feet, toes and fingers were remarkably similar to those of the koala bear, despite being different species and from different sides of the world.

They were unable to adapt to humankind destroying their habitat and eventually died out. The last sighting of the Megaladapis or koala lemur was over 500 years ago.