Not all dinosaurs went extinct - In fact, there are nearly twice as many species of dinosaurs as mammals to this day

Tuesday, March 25, 2014 by: David Gutierrez, staff writer
Tags: dinosaurs, birds, species diversity

(NaturalNews) Although it is popularly believed that all the dinosaurs went extinct roughly 65 million years ago, there are actually thousands of living species of dinosaurs still around today. Certainly there is no credible evidence of surviving large, scaly creatures like those we tend to think of when we hear the word "dinosaur" (even sightings of the Loch Ness monster do not count, as plesiosaurs are not actually a type of dinosaur). But by modern evolutionary classification systems, there is no scientifically credible reason for considering birds to be anything other than a specialized variety of dinosaurs.

Biologists now divide the dinosaurs into two major groups: the Ornithischia ("bird hipped") and the Saurischia ("lizard-hipped"). The lizard-hipped dinosaurs are further divided into the Sauropodomorpha (which includes the iconic massive, long-necked dinosaurs) and the Theropoda. Ironically, considering the label "lizard-hipped," it is this latter group that includes modern birds (as well as all the extinct bipedal dinosaurs such as Tyrannosaurus rex).

The classification of birds as a variety of dinosaur is supported by a wide array of fossils and other evidence. Features shared in common between birds and extinct Theropods include hollow, pneumatized bones; use of gizzard stones; nest-building and brooding behavior; flocking behavior and care for offspring. Many fossilized dinosaurs have been shown to have had feathers (including a close relative of T. rex!), and at least some extinct Theropods slept like modern birds, with the head tucked under the arms. Analysis of the structure of proteins and cell anatomy in fossilized soft T. rex tissue demonstrated that the famous dinosaur was more closely related to birds than to alligators. Some data even suggest that many extinct dinosaurs were warm-blooded and had four-chambered hearts like modern birds.

Of course, the exact process that led to the evolution of birds from other dinosaurs is unclear, and there are dozens of hypotheses that remain to be further tested by new fossil discoveries. Some researchers have hypothesized, for example, that birds went through a phase that involved wings on their feet as well as their arms; at least one has suggested that some larger extinct dinosaurs actually evolved from birds, and not the other way around.

So there you have it: The nearly 10,000 species of modern bird (compared with fewer than 5,500 species of mammal) mean that dinosaurs are still better represented on Earth than mammals. Of course, so are reptiles (9,000 species) and even amphibians (6,433 species).

Sources:

http://www.currentresults.com

http://www.amnh.org