The fossil record indicates that marine mammals returned to the oceans about?

Question

a.100 million years ago

b.400 million years ago

c.50 millions years ago

d.5 million years ago

Answer 1

Answer--> A

The answer should be a at the end of cretaceous time (135-65 million approx.)

ACCORDING TO

http://members.tripod.com/Geologi/Fossil...

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AN EXTRACT of the above mentioned link

http://members.tripod.com/Geologi/Fossil...

............................ LINK Extract.............................

The Mesozoic Era (225-65 million years ago), which includes the Triassic, Jurassic, and Cretaceous periods, is known particularly for the evolution of gigantic reptiles, both in the sea (Ichthyosaurus, Plesiosaur, and Mosasaur) and on land (Dinosaur). Flying reptiles (pterodactyl) and birds, as well as mammals, appeared during the Jurassic Period (190-135 million years ago). On land, forests of conifers and cycads had largely replaced the lycopod- and seed-fern-dominated forests of the Paleozoic Era. In the sea tiny calcite-armored, photosynthetic unicells called coccolithophorids appeared, and massive calcium carbonate (chalk) deposition began in the deeper oceans (ooze). The Cretaceous Period (135-65 million years ago) is the time of origin of two great groups of plants--the flowering plants (Angiosperm) on land and the diatom in water. Flowering plants changed the face of the Earth in many ways and triggered a great wave of evolution among the insects. At the end of Cretaceous time, the extinction of dinosaurs resulted in the spectacular evolution of terrestrial mammals, and giant sharks and marine mammals replaced large reptiles in the sea.

http://members.tripod.com/Geologi/Fossil...

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