When did primary bones develop during a dinosaurs life?

Scientists believe primary bones, also called fibro-lamellar bones, were formed during the rapid growth phase of a dinosaurs life in particular, when the dinosaur was young. These bones were very similar in structure to bones with blood vessels found in birds and mammals; the dinosaurs primary bones also contained blood vessels, which helped them to grow fast. These tissues are especially noticeable in fossil dinosaur leg bones.

When did Haversian (or secondary) bone tissue develop during a dinosaurs life?

In some dinosaurs, the primary bone tissue was later replaced by Haversian bone tissue in a process called remodeling. These tissues had many blood vessels with dense bony rings around them. This type of bone, similar to those of large modern mammals, had more strength and was more resistant to stress.

When did growth ring bone tissue develop during a dinosaurs life?

The growth ring bone tissue, found in some dinosaur bones and modern, coldblooded reptiles, look similar to growth rings found in trees. Tree rings grow each year, responding to changing seasonal conditions. By counting the rings, it is sometimes possible to tell the average age of a tree.

The presence of similar structures in certain dinosaur bones suggests the animals growth rates slowed down later in life. One interpretation is that the animals became more reptile-like. One major problem is interpreting a dinosaurs growth ring bones: unlike a growth ring on a tree, no one knows the amount of time represented by each growth ring in a dinosaur bone.

What do these three types of bone tissue indicate about dinosaur physiology?

The presence of these three bone tissue structures suggests dinosaurs had a unique physiology lying somewhere in between cold-blooded reptiles and warm-blooded birds and mammals. Perhaps this unique physiology made dinosaurs extremely adaptable, enabling them to dominate the land for around 150 million years.

Where are extremely large dinosaur bones being found and why?

Some of most consistently large dinosaur bone discoveries are being made in South America especially in northwest Patagonia, in Argentina. This includes such examples as the, Argentinosaurus and Megaraptor. Although scientists believe they know why these animals evolved differently from their northern counterparts, they truly dont know why the animals became so large.

Dinosaur bones are used for more than impressive museum displays. They can tell scientists a lot about how dinosaurs behaved and adapted to their environments (iStock).

What happened to North and South American dinosaurs over time?

One theory to explain the large South American animals involves locality. At the beginning of the Mesozoic era, all the land on Earth was merged into the continent of Pangea. During the Jurassic period, the supercontinent broke into the continent of Laurasia (which would eventually become North America and Asia) and Gondwanaland (eventually Africa, Antarctica, Australia, India, and South America). And not long afterward, South America and Africa began to split apart.

Most scientists theorize these splits were the pivotal points in these dinosaurs evolution. For a short time, the dinosaurs crossed a land bridge from North to South America; geologic activity eventually destroyed the bridge, cutting off access and allowing creatures like the migrated Megaraptor to evolve separately in the south. The North American animals, such as the Tyrannosaurus rex, developed a specialized skull, forelimbs, and pelvis; the South American dinosaurs, such as the Giganotosaurus, maintained most of the general features of their ancestors and became much larger.

Other scientists believe that southern Megaraptors and their northern counterparts originally evolved separately from common ancestors. They suggest that the reason why the two carnivorous giants like the Tyrannosaurus rex and Giganotosaurus resembled each other was possibly due to similar environmental conditions (this is called parallelism); when the landmasses began to break up, the animals continued to evolve separately.

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