The first of these were initially described as simple filamentous protofeathers, which were reported in dinosaur lineages as primitive as compsognathids and tyrannosauroids. Some researchers have demonstrated the presence of color-bearing melanin in the structures—which would be expected in feathers but not collagen fibers.
The Evidence for Endothermy in Dinosaurs Dr. We shall list some of these and objectively mention some problems with each. Top ten hypotheses Given: Studies on modern animals seem to show that metabolic rate is proportional to maximum rate of locomotion.
Dinosaurs were built to move fairly quickly, so they must have had high metabolic rates. We do not know how fast dinosaurs really moved. See our dinosaur speeds page to see why. Ecological studies suggest that today's endotherms mammals and birds generally outcompete ectotherms in their area.
Dinosaurs evolved alongside mammals, so they must have been endotherms in order to compete with mammals adequately for the million years that they coexisted.
We don't know that the "Given" always applies; there have been few conclusive studies of endotherm-ectotherm competition.
So the "Given" has not been conclusively established yet.
Also, just because certain ecological patterns are evident today does not mean that they must have always applied. Dinosaurs must have been endotherms; an erect posture must be indicative of endothermy.
Erect posture has not been shown to be necessary for endothermy, or vice versa. The two factors seem to be correlated, but cannot be assumed to always occur together.
Some endotherms have a more sprawling posture such as many small mammals ; the earliest mammal relatives the basal synapsids certainly did not have an erect posture.
Similarly, some modern ectotherms, chameleons for example, have an erect posture. Studies indicate that large brain size is correlated with endothermy.
Theropod and ornithopod dinosaurs had larger than normal brains for "reptiles"so they must have been endothermic. Large brain size may be correlated with endothermy, but it is correlated with many other features not necessarily related to endothermy.
Not an empirically supported "if Also, the data on dinosaur brain size is scant at best; being measured from the few complete skulls available.
Many dinosaurs had quite typical reptile-sized brains. Ectotherms are not normally found at high latitudes it's cold. Dinosaur fossils are known from high latitudes, so they must have been endothermic to cope with the cold. The high latitudes Alaska, Antarctica, etc. Even if they were somewhat cold, dinosaurs could have migrated there in the summer when it was warmer, and emmigrated during the cooler winter.
Also, the climate in the Mesozoic was generally warmer and milder than today we're just recovering from the last ice age, remember.
Finally, today's snakes, lizards, turtles, the tuatara, and crocodiles do enjoy a surprisingly broad latitudinal distribution. · For the next century, claims that birds were dinosaur descendants faded, with more popular bird-ancestry hypotheses including 'crocodylomorph' and 'thecodont' ancestors, rather than dinosaurs or other monstermanfilm.comy of research · Current knowledge · See also · References · External linksmonstermanfilm.com Way back in , British biologist Thomas Henry Huxley was the first person to propose that dinosaurs were feathered, and that they were the ancestors of modern monstermanfilm.com://monstermanfilm.com · After the impact, fossil evidence from North America suggests ferns were the major flora for about years.
“When we started this study, we didn’t know where it would lead,” Field monstermanfilm.com://monstermanfilm.com · They found eggs laid by dinosaurs closely related to birds were coloured, while more distantly related dinosaurs were plain Findings suggest modern birds inherited their eggshell hues from monstermanfilm.com · Birds: The Late Evolution of Dinosaurs.
Evidence that birds evolved from the carnivorous predators that ruled the Mesozoic ecosystems is plentiful and it comes from disparate lines of evidence.
Traditionally, the prime source of evidence in support of this scientific view was the similar shape of the bones of birds and a variety of monstermanfilm.com /dinosaurs/birds-late-evolution-dinosaurs.
How Dinosaurs Shrank and Became Birds. Modern birds appeared to emerge in a snap of evolutionary time. But new research illuminates the .