How do scientists know that dinosaurs were reptiles?

Question

It's possible that they could be mammals, even marsupials too.

Answer 1

Scientists generally believe that dinosaurs were NOT reptiles, but an intermediary type of animal between reptiles and modern birds.

There is still some debate about whether they were cold-blooded (like reptiles) or warm blooded (like mammals and birds).

But it is pretty clear that dinosaurs and mammals were different branches in the evolutionary tree. The two branches are known as the diapsids and synapsids. The diapsids are distinguised by one hole in the skull behind the eyes and this branch can be seen to develop from reptiles to the dinosaurs and later to birds. The synapsids have one hole in the skull behind the eye, and these became the therapsids, and later the mammals.

The source below has a lot of details in the structural differences that separate dinosaurs from all other types of animals.

Answer 2

Because we have enough evidence to know they shared charachteristics with reptiles. We have found fossilised Dinosaur skin, so we know they had scaly skin, so that suggests reptile and discounts amphibian. We have found fossilised dinosaur eggs, so we know they laid eggs with hard outer shells, just as reptiles do. There is no evidence of hair, so that discounts mammals. Birds evolved from Dinosaurs. They certainly didn't have gills etc, so weren't fish. That leaves reptiles by simple process of elimination/ We can also assess their bone structure. We can look at their bone structure, how the bones fit together, and there are also grooves indicating where blood vessels and muscles may have attached. It is possible to divide dinosaurs into 2 groups: Reptile-like ones and Bird-like dinosaurs. The reptile-like ones obviously have structures similar to modern day reptiles. The bird-like dinosaurs is where the evidence that birds descended from dinosaurs comes from. However, before they evolved into birds, they were reptiles. As for their circulatory system etc, there is some debate. The evidence from looking at fossils indicates that most were cold-blooded, like modern reptiles. However, a number of paleontologists claim that some species show signs of being warm-blooded, and there is some evidence to support this view.

Answer 3

How do we know about dinosaurs? The only way we know about dinosaurs is from studying fossils. Animals and plants may become fossilized if they are buried in sand or mud soon after death. Even so, only the hard parts of the body (bones and teeth) usually remain to be fossilized because scavengers and bacteria destroy the fleshy parts of the body. In addition to bones and teeth, footprints or tracks of dinosaurs may be preserved in sandstones or mudstones, which were once soft sediments. Scientists can estimate the walking, running or even wading speed of certain dinosaurs from a series of tracks, as well as dinosaurs size and whether they lived alone or traveled in groups. The bones and tracks of a particular dinosaur are rarely preserved in the same place, so paleontologists must compare the shapes of foot bone and the footprints to make a match. Other dinosaur fossils include skin impressions, eggs, stomach stones, and droppings, but these are relatively rare. Some dinosaurs (the sauropods) apparently swallowed stones to help grind up fibrous food in their stomach, much like chickens do! The large stomach stones (or "gastroliths") became smooth and highly polished after grinding food for a while, like rocks in a tumbler. Scientists also study fossilized droppings (or "coprolites") to see what kind of foods the dinosaurs ate.

Answer 4

"Reptile", "mammal" and "marsupial" are merely words that we invented to describe groups of animals with specific traits. Since those traits that appear in many dinosaurs most closely resemble what we had defined as "reptileness", it seems reasonable to believe they were reptiles!

Answer 5

They don't know for sure, but fossilized skin impressions and bone structure when compared to that of contemporary animals have given them that suggestion.

There is another school of thought that suggests that at least some dinos being birds in actuality, based on the fact that their pelvises are reversed like a bird's...

Answer 6

Animals can be classified based on structural details of their skeletons. The precise details and nomenclature get rather involved, but you might get an idea of it by looking at this page and its links:
http://www.enchantedlearning.com/subjects/dinosaurs/dinoclassification/index.html

Answer 7

from their fossilized chambered hearts which are like that of lizard species from around the world, bone fragments of the babies link them to anamilia reptilia, if there is such a thing as that wording. anyway, there are many clues and look at how long and thick their tails were! like lizards, but oversized!

okay, you know now that i'm kind of talking out of my @$$ but that's the general idea of how they know!

Answer 8

when they dig up the bones they used that DNA and compared it to other animals and it was very similar to that of the reptile family

Answer 9

They Don't, they assume. And we just believe.

Answer 10

cuz they look like lizards