Why haven't some species evolved like man has? Why haven't modern amphibians evolved to become reptiles? We need you to answer this question! It really makes you wonder: why haven’t crocodiles evolved? Also: If you're denying evolution, then how come antibiotics don't work as well as they used to back in the 60's? Dinosauria is a well-supported clade, present in 98% of bootstraps.It is diagnosed by many features including loss of the postfrontal on the skull and an elongate deltopectoral crest on the humerus. If evolution is true why didn't they evolve from like 500 million years ago. As stated above, the K/T Extinction wiped out land-dwelling dinosaurs and pterosaurs, as well as sea-dwelling mosasaurs (the sleek, vicious marine reptiles that populated the world's oceans toward the end of the Cretaceous period). I was thinking that evolution (ie random mutation) was inevitable. I know they allegedly evolved from an extinct common reptile, which evolved from something like a crocodile. The estuarine crocodile (Crocodylus porosus) is a semi-aquatic reptile, living mainly in rivers, mangroves and estuaries. Crocodiles actually have evolved, they’ve just changed in really small increments over the years. ... There’s a persistent notion that crocodilians evolved slowly and haven’t changed much, Dr. Brochu noted. Dinosaurs evolved within a single lineage of archosaurs 243-233 Ma (million years ago) from the Anisian to the Carnian ages, the latter part of the middle Triassic. According to evolution species change to fit their environment and since the environment changed a lot why haven't they also. It’s an excellent example of when evolution reaches it’s peak. Or we can think of flying as something very advantageous, but flight has only evolved four times (insects, pteurosaurs, birds and bats; or five, if we include our flying machines). Check the fossil record. They haven't followed one chain of evolution. The crocodile is at the top of its food chain and has no need for large evolutionary changes. ! Why? My question is - since we still have crocodiles... why haven't they re-evolved into those ancestors again, and into dinosaurs again? It seems their respiratory tract (a tracheal system) can't deal with salt water. Okay, I'm with the niche argument - I was going to mention crocodiles and the like.. it's just that 20 million years is a long time - I thought they might have developed a few "mods".. maybe they did? Crocodiles are a close living relatives of birds, but compared to their feathered cousins, they are stuck in the past, scientists claim. What do you say? So "you can't always have what you want". Re 2nd Detail: They have. Crocodiles are also in our modern world and seem pretty much exactly the same. Take dinosaurs. Crocodiles were radically different tens of millions of years ago. Crocodiles actually have evolved, they’ve just changed in really small increments over the years. Why Crocodiles Are Not Just Living Fossils. Shouldn't they have evolved frickin' laser beams on their heads by now? How crocodiles survived in a dinosaur's world: Jurassic ancestors 'ran around like DOGS’ to escape predators and ate PLANTS. The crocodile is at the top of its food chain and has no need for large evolutionary changes. Along with pterosaurs and dinosaurs, crocodiles were an offshoot of the archosaurs, the "ruling lizards" of the early to middle Triassic period; needless to say, the earliest dinosaurs and the earliest crocodiles resembled one another a lot more than either resembled the first pterosaurs, which also evolved from archosaurs.