by BlackSwan of Memphis 9 Replies latest jw friends
My 4 year old has a strong interest in dinosaurs lately. Well, it's been lasting for a good few months.
I've bought books and checked some out of the library, done internet searches.
The thing is some of the research/books say, 'yes, dinosaurs were reptiles.' other sources say they weren't.
I'm wondering if any of you have researched this topic and what you came up with in regards to this specific topic.
I'm not sure what to think.
I guess it is all on what clasifies something as a reptile, many now are say our modern day bird is a decendant of the dinosaur.
I guess we could call it a reptile from which the bird evolved which is not a reptile but has similarities .
Indeed ...
There still exists to this day much controversy regarding this issue.
Much of it stems from the hypothesis that Dinosaurs were Endothermic (Cold-blooded).
Before approximately 1960, almost all scientists believed the theory that their temperature was determined by that of the external environment. Scientists thought this because they had decided that dinosaurs were reptiles, and all modern reptiles are cold-blooded. (It should be noted that the term "reptile" has fallen out of favor in the modern, cladistic view, denoting as it does a paraphyletic group; however, most people still understand what is meant by a reptile, and I will use the term throughout in its traditional sense, making no pretense that it designates a natural clade.) Alligators and crocodiles are the most closely related non-dinosaurian archosaurs, and they are cold-blooded. Then people began to look further, and some of them decided that it was not so easy. Dinosaurs were unusual reptiles at best. They do not look like modern reptiles. They did not walk like modern reptiles. It had been suggested almost a century ago that birds were the direct descendants of dinosaurs, and they are indisputably warm-blooded; in fact, in the cladistic view, birds are dinosaurs. Maybe there was more to the story.
Several scientists proposed the "inertial homeotherm" idea. They said a big dinosaur could keep an even body temperature just because it was so big. According to Colbert and colleagues, a medium-sized dinosaur exposed to day and night temperatures similar to those found in Florida today would take 86 hours to change its temperature by 1°C. They based their estimates on experiments with alligators tied up out in the sun. Mesozoic climates were far more equable than they are now. Clearly, by moving from sun to shade, as modern ectotherms do, a fine degree of temperature control could be achieved without invoking a high metabolism.
Conclusion: Indisputable evidence does not exist for warm-bloodedness in all types of dinosaurs. However, it is highly unlikely that all dinosaurs were cold-blooded, either. Morphological and postural evidence, bone histology, ecological information, and brain/body size relationships indicate that we cannot make sweeping generalizations about dinosaurian metabolism. Most likely it varied between groups. Dinosaurs spanned the spectrum from inertial homeotherms to active, endothermic birds.
But that's just me ... I always encourage anyone to do their own research ...
Much of it stems from the hypothesis that Dinosaurs were Endothermic (Cold-blooded).
I apologize for the error .. I meant Ectothermic.
thanks frankie, I have read that bit of info as well throughout some of the books I've been reading.
Maclice: Wow, you really summed it up quite nicely. Maybe you should write a dinosaur book! I think I'm going to cut and paste this into the books.
However, it is highly unlikely that all dinosaurs were cold-blooded, either.
It seems like none of the authors (scientists?) can agree on the fact so I'm not finding much agreement.
In addition to what has already been said, some dinosaurs exhibited bone characteristics (channels though their bones) which suggest that, if not fully warm blooded, they were evolving in that direction. Some dinosaurs demonstrated more reptilian characteristics than others. Even in the 19th centuries, it was recognized that dinosaurs fell into two classes, those with reptilian pelvis, and those with avian (birdlike) pelvis. These classes are termed Sauriscia and Ornithscia, respectively. Regarding the link between birds and dinosaurs, this is hard to dispute in the face of anatomical evidence. There are many dinosaurs, such as Ornitholestes and Struthiomimus (its name means "ostrich-mimic"), which have very birdlike skeletons. Additionally, the earliest known bird, Archeoptryx, does have crude feathers, but retains many reptilian characterisitcs such as toothed jaws (instead of a beak), a lizardlike vertebrate tail (although with feathers growing from the sides), and fingers with claws in its wings. If the feathers were not visible, Archeoptryx would be considered another small dinosaur, like a smaller Velociraptor. Recent discoveries have demonstrated that other dinosaurs, including Velociraptor, also had feathers, although no one suggests that they could fly. So, are dinosaurs reptiles? This depends on how you define "reptile", but many dinos would classify as a special type of reptile. Are dinosaurs birds? Well, SOME dinosaurs could be said to be very closely related to birds. It does seem safe to say that all birds are descended from one branch of the dinosaur family. Hope this helps a little.
Thanks Gaiagirl! Hey it all helps.
So, are dinosaurs reptiles? This depends on how you define "reptile", but many dinos would classify as a special type of reptile.
This is like what Frankie said. I can see how it can get complicated.
I suppose it would be better to not classify them as either or. But to a kid explaining the complexities of cold blooded vs warm blooded in addition to the technical stuff with bone structure and whatnot, I can see why it's tempting to bring it down to "reptile".
I have read a little about the dinosaur bird connection. Thanks for the further info! I have to say I was pretty surprised to read that in these books. I had always just pictured the gators as being direct descendents and didn't think much more of it.
So then were the Archaeoptryx and the other winged dinos considered early birds? I had read in one book that they (although I'm beginning to get the impression that the "they" doesn't necessarily mean much) don't consider them birds, but rather dinos. (you guys sound as if you know more then them, lol)
This should be settled soon. Scientist are now examining soft tissue found (amazingly) inside a T-rex leg bone. They say that the blood vessels are virtually identical to those found in the leg of a modern Ostrich.
Archeoptryx is generally considered to be a bird, however, Pteryodactyls (the name means "wing-finger") are not, because the skeletal structures of their wings are different in that their wings are formed by a membrane of skin, supported by a very long finger bone, similar to a bat. They may have had feathers for thermal insulation, but did not need feathers to fly. Birds, including Archeoptryx, do not have the long finger bone or the membrane of skin. Their wing surface was formed by the feathers themselves, and the feathers are attached to the arms. If you removed the feathers, Archeoptryx could not have flown at all, just like any other bird. So Pterodactyls are considered to be another branch which are usually called "flying reptiles" and not "birds". In a similar manner, the aquatic creatures such as Plesiosaurus, Mososaurus, and others are usually termed "marine reptiles" and not dinosaurs, just as modern sea turtles are not considered dinosaurs, although they can reach a fair size.
Scientist are now examining soft tissue found (amazingly) inside a T-rex leg bone. They say that the blood vessels are virtually identical to those found in the leg of a modern Ostrich.
Oh wow that's pretty cool. How do they figure that out?
Archeoptryx is generally considered to be a bird, however, Pteryodactyls (the name means "wing-finger") are not, because the skeletal structures of their wings are different in that their wings are formed by a membrane of skin, supported by a very long finger bone, similar to a bat. They may have had feathers for thermal insulation, but did not need feathers to fly. Birds, including Archeoptryx, do not have the long finger bone or the membrane of skin. Their wing surface was formed by the feathers themselves, and the feathers are attached to the arms. If you removed the feathers, Archeoptryx could not have flown at all, just like any other bird. So Pterodactyls are considered to be another branch which are usually called "flying reptiles" and not "birds".
Before I went to bed last night I was looking through the books at the flying reptiles and then at Archeopteryx and could see the difference. The Pteryodactyls remind me more of bats. While Archeopteryx definitely was bird like.
In fact I was looking through this one book published, I think, by DK. It's an Atlas of Dinosaurs. Wow. This is such an interesting topic. It seems quite involved and complicated. There's a lot to it.
