Verified answer

> Are turtles or crocodiles dinosaurs.

No and no.

> And why don’t dinosaurs exist anymore?

The Chicxulub impact event cooked half of them, and the rest died off in the aftermath of the impact event: tsunamis, then "nuclear winter."

The ancestors of today's birds survived, and thus birds are the remaining extant or the Dinosauria clade.

> What makes a dinosaur a dinosaur?

It's an archosaur with the hind limbs "under" the body, or an animal that is descended from such a dinosaur.

> Wouldn’t a turtle or crocodile be one

No and no. A crocodile is an archosaur, but Crocodilians split from the lineage that led to dinosaurs, and are not dinosaurs.

> wouldn’t they come back by now

No. Things that are dead don't come back.

> just like the very first animal to live in the world would

Sponges and Placozoa are still with us because they never became extinct, and similar descendants were produced in each generation.

Spongebob Squarepants himself, however, was not alive a half billion years ago.

> the first animal it was just made by nothing

No. The first sponges were descended from earlier choanozoa.

“Are turtles or crocodiles dinosaurs. (sic)”

No, they are not dinosaurs.

“And why don’t dinosaurs exist anymore?”

They went extinct ca. 65 million years ago. They were wiped out because of an asteroid strike on the Earth at Chicxulub, Yucatán, Mexico.

“What makes a dinosaur a dinosaur?”

They belong to the archosaurs, which are different from other reptiles.

“Wouldn’t a turtle or crocodile be one …”

No, they belong to different groups of reptiles.

“… also if the dinosaurs was (sic) wiped out by an asteroid or however it happened it has been millions of years wouldn’t they come back by now just like the very first animal to live in the world would, because you can’t give birth to the first animal it was just made by nothing.”

No, when anything goes extinct it stays extinct. No extinct species has ever re-evolved. It is generally accepted by evolutionary biologists if you could press STOP, REWIND to the beginning of evolution and press PLAY to start the process de novo that evolution would not produce the same species and may very well not lead to the evolution of humans.

“I’m confusing myself here.”

At this point in your question I think you have managed to confuse many.

Dinosaurs were Saurians, a form of reptile.

While both crocs and turtles are also reptiles, the alligators/crocodiles are crocodilians, and turtles are Testudines. Two completely different families.

Dinosaurs were only one branch of the reptiles. Turtles and crocodiles were other branches, and they made it through the extinction. Most dinosaurs did not, only the avian ones survived. We call them birds.

You can look up their family trees. Turtles and crocodiles were not closely related to the dinosaurs.

FWIW, animals of roughly 55 lbs or less made it through, those over did not. We are talking species here, a few members survived and diversified over the 65 million years since.

You'll need to develop a foundation in evolution knowledge before pursuing your question. You are correct, you are confusing yourself here due to lack of knowledge.

Turtles are probably anapaid reptiles, meaning they are descendants of the earliest branch of reptiles to have evolved. They are called anapsid because they have no temporal opening in their skull.

Another branch of reptiles is synapsid. The synapsids include such well known fossils as Dimetrodon, which has a sail-like frill on its back. Synapsids are now extinct, except for one branch that led to the ancestor of mammals. Synapsids have a single temporal opening in their skull. Mammals, including humans, are the descendants of synapsid reptiles.

Another branch of reptile is known as diapsids, and they have 2 temporal openings in their skull. Living diapsids are lizards, snakes, crocodilians and the tuatara. The ancestor of birds was also a diapsid, but it belongs to a special group of diapsids known as archosaurs, or ruling reptiles. Archosaurs include crocodiles and dinosaurs. That means the closest living relative of birds are crocodiles and alligators.

Dinosaurs are not a well defined group. There were 2 great groups of dinosaurs, known as saurischians, or lizard-hipped dinosaurs, and the ornithischians, or bird-hipped dinosaurs. Many modern scientists believe that both groups of dinosaurs share a common ancestor but some of the greatest paleontologists who ever lived do not think so. George Gaylord Simpson and A. S. Romer both think that the 2 groups of dinosaurs evolved independently of each other. About the only similarity between these 2 groups of dinosaurs is that they evolved from ancestors that walked on 2 legs. The 4 legged dinosaurs evolved from ancestors that walked on 2 legs.

Dinosaurs evolved in the late Triassic and they were the dominant land animals for over 150 million years. Then 65 million years ago, a giant meteor the size of Mt. Everest struck the earth at high speed. The impact was the equivalent of 1 billion atomic bombs exploding all at once. The earth's atmosphere was heated to oven-like temperatures. All dinosaurs, and all enantiornithine birds were wiped out by the hot temperature. Even many mammals were wiped out. The survivors were either animals that were spending a lot of time underground (e.g. invertebrates, lizards, snakes, toads, shrew-like mammals and multi-tuberculates or rodent-like mammals), or they spent a lot of time in the water (e.g. aquatic animals, crocodiles, frogs, turtles shorebirds and the platypus). They survived because heat rises, so temperature underground was cool enough to allow them to survive. Temperatures in or near the water was also cool, since water takes a lot of energy to heat up.

A bird Is he closest ancestor to a dinosaur. There are several theories on how dinosaurs became extinct. The asteroid, ice age, volcano eruption. Scientists believe that different species of dinosaurs where extinct at different times.. . EX.... The Do-Do bird went extinct,, but not all birds. It would take a long time for all birds to go extinct. So it took a while for all the dinosaurs to go extinct and by many various reasons. and eventually evolved into the animals we know today depending on their environment.

Turtles are not dinosaurs, but some people say that crocodiles are or are very much like dinosaurs. To my understanding it has some thing to do with their hips but I believe that most dinosaurs had hips like birds instead of lizards.

Reptiles were classified according to orbital fenestrae

Turtles, crocodiles, and dinosaurs are all examples of reptiles. A crocodile is not a dinosaur, just as no dinosaur was a crocodile. Your question is a little like asking whether horses are cows. They are related, but definitely not the same thing. No reason to expect that the very same species would re-evolve after extinction. The passenger pigeon became extinct in 1914. We still have lots of other kinds of birds, but we would not expect new evolution to produce an exact copy of the passenger pigeon.