The reptiles to me look exactly like dinosaurs, their skeleton resemble fossils and they are cold-blooded.
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Many dinossaurs were warm-blooded.
Also, one of the traits of all reptiles are that they have their limbs in a 90 degree shape, since they stick out of the body to the side, then down. Dinossaurs had their limbs directly down.
“Using proper terminology, birds are avian dinosaurs; other dinosaurs are non-avian dinosaurs, and (strange as it may sound) birds are technically considered reptiles.”
They are all related. Dinosaurs developed over many different periods and many millions of years. They died out or they evolved. They’re all related if you go back far enough, though.
Reptile-like creatures evolved into reptiles and dinosaurs, and dinosaurs later evolved into birds. So reptiles and dinosaurs are sort of cousins. As to why dinosaurs look like reptiles – the reason for that is because we have traditionally depicted dinosaurs as resembling reptiles, and the reason for that is because someone in the 19th century thought that they probably resembled reptiles. In fact, we don’t really know for sure what dinosaurs looked on the outside. There have been finds in recent decades which suggest that many dinosaurs had feathers, i.e. that they looked more like birds.
It depends on how exactly you define these groups. If you group species based on their features, then it’s because birds share a lot of features with dinosaurs that other reptiles don’t like being warm-blooded, certain parts of their skeletons, feathers, etc. More often though, species are grouped based on their evolutionary relationships to each other, in which case it’s because birds evolved from dinosaurs and other reptiles didn’t.
It is because of how those terms are defined.
The usual definition for dinosaur is cladistically. This means they pick two examples like T-Rex and Triceratops and say a dinosaur is everything in the smallest family tree that has both of the examples.
Basically going back to the last common ancestor of those examples and say that was the first dinosaur and everything descended from it is also a dinosaur.
Grouping things together this way makes a lot of sense, but it leads to some funny results like including birds.
It also excludes some extinct animals commonly mixed in with dinosaurs like flying or swimming reptiles that lived along side them or creature like the large mammal like reptile with a sail on it back Dimetrodon which live long before them. It also excludes crocodiles and lizards and other living and extinct reptiles that share things in common with them.
It makes sense though.
The word dinosaur in casual conversation is usually understood to refer to those creatures that have been extinct for 66 million years and not birds.
Usually the term non-avian dinosaur is used for those if you want to be pedantic.
Technically though a sparrow or a chicken is a dinosaur. Technically a falcon is a carnivorous dinosaur that hunts other dinosaurs as well as small mammals and reptiles. Technically the dodo and the passenger pigeon are examples of extinct dinosaurs.
But that is just if you want to be overly pedantic about things.
The whole idea of grouping creatures together based on common descend, where all creatures that share an ancestor are in a group results in problems in other areas too. For example the different creatures we call ants and wasps are so mixed up with each other, that you can’t create a cladistic definition for only wasps or ants that would not either include the other or exclude some animals we call ants or wasps.
Than there are places were we really want to exclude some animals for a definition because we don’t like the implications of grouping all primates or great apes or chimpanzees together.
Then there are “fish”. You can define fish that way at all.
If you go by clades either fish aren’t a thing or they are everything. Neither is a very useful definition.
1) Scientist are still debating if Dinosaurs are warm or cold blooded. We don’t really have good direct evidence.
2) They look like reptiles because that’s how we depicted them in our culture. In reality we don’t really know how they looked. What their skin looked like, did they have feathers, what color they were, etc. We have some information about some of them, but fossils evidence outside of their skeleton is hard to find.
You should look at the sketch of current living animal by Palaeoartist C. M. Kosemen. It show how we can be so wrong about how an animal look with only the skeleton as information. He depict animals like a snake, an elephant, a cat, etc And they don’t look at all like they do in reality. We more than likely are doing exactly the same things with Dinosaur.
There is also some depiction of Dinosaur with more Avian feature, but at the time that Dinosaur become really popular in our culture, most depiction were reptilian in nature, so this depiction remain stronger in our culture today.
Think of it like a family tree.
Great-Grandpa and great-grandma were Reptile-Things. I say “Reptile-Things” because they aren’t really reptiles, but they’re close.
They had two children: Many-Reptile and Dino-things. Most reptiles we know of today are the grandchildren of Many-Reptile. Dino-Things children include Dinosaur and Crocodilian. Dinosaur’s children are Birds, while Crocodilian’s children are Crocodile, Alligator, and their siblings (which we call “reptiles”; but are not the grandchildren of Many-Reptile).
In real life, there were a lot more generations in there – but the idea is the same.
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We don’t know where certain things come from. We know Dino-Things didn’t know how to make feathers or warm blood; but Birds do. We think Dinosaur learned both at some point along the way; but we don’t know for sure.
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