How do you distinguish between dinosaurs and non-dinosaurs when discussing reptile-like prehistoric creatures?

Question

I am confused as to what the difference is between large dinosaur-like prehistoric creatures (Such as the Dimetrodon) and actual dinosaurs (Like a Tyrannosaurus). On Discovery Channel specials, I'll see a show with two large creatures, and they'll say that one is a dinosaur, but another is not. Is there some sort of scientific distinction? I assume there is, but what is it?

Answer 1

Like with all taxonomic categories, there are anatomical features which define the groups. Dinosaurs are defined by a number of skeletal features such as in the following link. Going up a level, the Archosauria have other defining "synapomorphies" and so on. Pelycosaurs like Dimetrodon are actually quite different, being closer related to mammals than dinosaurs. I'm sure there are anatomical differences between them and dinosaurs that even you and I could immediately grasp. But I can't remember much anymore.... one biggey though is in the legs - the mammal-like reptiles having the more splayed stance, like lizards.

Answer 2

Good question. I always used to assume that all giant reptiles in prehistoric days were dinosaurs but Dinosauria is an actual clade (fancy word for a grouping of animals) and marine 'dinosaurs' like the marine ones like Icthyosaurus, the flying ones like Pteranodon and even other land reptiles are not included within that group. Get yourself a book on dinosaurs that has a family tree and you'll be able to look in to it.

Using accurate terms when grouping animals according to their families continues to be a problem - in fact as Birds ARE Dinosaurs, scientists will often use the awkward term 'non-aviant dinosaurs' to refer to the lumbering behemoths like T-rex and co.

Answer 3

Yes there is. Dinosaur means Giant Lizard. The distinctions generally lie in the skeletal structure and features.

Answer 4

Simple. The 6 days of creation were not 24 hour days. I can prove that even with the bible. A day of a 24 hour rotation was not even made until the fourth day. This verse begins the fourth day of creation. Gen 1:14 "Then God said, "Let there be lights in the expanse of the heavens to separate the day from the night, and let them be for signs and for seasons and for days and years;" So that proves the first 3 days were not 24 hour days. The Apostle Peter says,"A day is as a 1000 years to the Lord". So put all that together and there is the story of the beautiful system of evolution beginning it's process. Somehow the dinasaurs were part of that process. Adam and Eve were not the first created homo sapiens. They were the first humans that had a soul, an awareness of God and of right and wrong. Hence God says on the 6th day, "Let us make man in our image," because in that "day" (1000's of years?) man evolved to be the only animal to be like God knowing good from evil.

Answer 5

There are classified periods of time where the most change occurs. The difference in the animals might be of help, because when I think of dinosaurs at their prime, or just narrowing down i think of the jurrasic stage.