Showing posts with label cretaceous. Show all posts
Showing posts with label cretaceous. Show all posts

Sauropods Were Ideally Suited to Grow Large

The largest animals ever to roam the Earth were sauropod dinosaurs in the Jurassic and Cretaceous eras.  They did not eat meat.  Despite having to constantly eat grass and leaves the heaviest reached 50 tonnes.

The periods going back from the present are Cenozoic, Cretaceous, Jurassic, Triassic and Paleozoic.  The last four are grouped into the Mesozoic era.  It is in this general broad time frame that the gigantic dinosaur arose and died off.

Though for the most part these creatures walked with their heads in an horizontal position, for feeding it is presumed that they reached up vertically to feed on young branches and leaves high in the trees.  Other herbivores could not reached up to this rich food source.  Mammals had not yet risen.  Giraffes appeared much later.

Having plenty of food meant the sauropods could evolve and become very large.  Their bones were light and with a small head the neck became long.  They swallowed food whole so they had tiny jaw muscles.  Food remained in the body a long time.  This enabled thorough digestion of leaves and even some wood.  Not masticating in itself left more energy to grow bigger.

They were bird-like, having an efficient respiratory system; thus the significant body heat was dissipated.  The high basal metabolic rate meant they could live longer and survive to become adults and reproduce.  Having many young from eggs maintains a species more effectively than the mammalian way of breeding.
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"Crocodile Headed" Dinosaur Found in Australia

A dinosaur with a head remarkably like modern crocodiles has been found in Australia. It didn't walk on all fours though. It stood upright on two legs like a T.rex. In the Cretaceous 146 million years ago they wandered over most of the Earth. This is the first time they have been found so far south.

It seems this group of dinosaurs, spinatosaurids, were really mobile. This find confirms that all dinosaurs travelled long distances populating great area of the planet. The fossils were overlooked since they were found in the 1990s. Paul Barrett of the Natural History Museum London was examining samples at the Museum of Victoria. He noticed that the vertebra was the same as Baryonyx walkeri a long clawed spinatosaurid found in Europe.

A new look at other dinosaur specimens showed examples in old Gondwana which included Australia and Laurasia, so millions of year ago different species of dinosaur lived alongside each other right across the globe. At the end of the Cretaceous the land mass separated and species began to differentiate much more because of isolation.
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Science