The first of these were initially described as simple filamentous protofeathers, which were reported in dinosaur lineages as primitive as compsognathids and tyrannosauroids.
Read in another language Evolution of dinosaurs This article gives an outline and examples of dinosaur evolution. For a detailed list of interrelationships see Dinosaur classification.
It is diagnosed by many features including loss of the postfrontal on the skull and an elongate deltopectoral crest on the humerus.
According to the new classification, the original dinosaurs, arising million years ago, were small, two-footed omnivorous animals with large grasping hands.
Descendants for the non-avian dinosaurs lasted until 66 million years ago. Crocodiles are also descendants of mid-Triassic archosaurs.
With that definition, the pterosaurs and several species of archosaurs narrowly miss out on being classified as dinosaurs. The pterosaurs are famous for flying through the Mesozoic skies on leathery wings and reaching the largest sizes of any flying animal that ever existed.
Earliest dinosaurs Edit The first known dinosaurs were bipedal predators that were metres 3. Saturnalia may be a basal saurischian or a prosauropod. The others are basal saurischians.
Eoraptoran early saurischianB Lesothosaurusa primitive ornithischianC Staurikosaurus Saurischia pelvis, D Lesothosaurus pelvis It is clear from this figure that early saurischians resembled early ornithischians, but not modern crocodiles.
Saurischians are distinguished from the ornithischians by retaining the ancestral configuration of bones in the pelvis. Another difference is in the skull, the upper skull of the Ornithischia is more solid and the joint connecting the lower jaw is more flexible; both are adaptations to herbivory and both can already be seen in Lesothosaurus.
Saurischia Edit Setting aside the basal Saurischia, the rest of the Saurischia are split into the Sauropodomorpha and Theropoda. The evolutionary paths taken by the Theropoda are very complicated.
The Dinosauriaa major reference work on dinosaurs,  splits the Theropoda into groups Ceratosauria, Basal Tetanurae, Tyrannosauroidea, Ornithomimosauria, Therizinosauroidea, Oviraptorosauria, Troodontidae, Dromaeosauridae and Basal Avialae in turn.
Each group branches off the main trunk at a later date. See Dinosaur classification for the detailed interrelationships between these. Sauropodomorpha Edit The first sauropodomorphs were prosauropods. They had lengths of 2. Features defining this clade include a ratio of forelimb length to hindlimb length greater than 0.
Most sauropods still had hindlimbs larger than forelimbs; one notable exception is Brachiosaurus whose long forelimbs suggest that it had evolved to feed from tall trees like a modern-day giraffe.
The Cretaceous sauropods form two groups. The latter clade consists of series of nested subgroups, the Titanosauriathe Titanosauridae and Saltasauridae.
The sauropods are famous for being the largest land animals that ever lived, and for having relatively small skulls. The enlargement of prosauropod and sauropod dinosaurs into these giants and the change in skull length is illustrated in the following charts.
Dinosaurs used in creating these charts are in date order: With the exception of Argentinosaurus included to fill a gap in timethese graphs show only the length of sauropods for whom near-complete fossil skeletons are known.
It doesn't show other very large sauropods see Dinosaur size Sauropods because these are only known from very incomplete skeletons.Dinosaurs were once thought to be the cold-blooded kings of the Mesozoic era.
But new research on their growth rates suggests the prehistoric beasts grew just as fast as mammals, indicating they. · Feathers, once thought unique to birds, must have evolved in dinosaurs long before birds developed.
Sophisticated new analyses of these fossils, which track structural changes and map how the specimens are related to each other, support the idea that avian features evolved over long stretches of caninariojana.com · Most mammals have worse color vision than reptiles or birds, and mammals’ eye shapes and retinas suggest that their distant ancestors were adapted for night vision.
Why? Blame the caninariojana.com://caninariojana.com · The possibility that dinosaurs were the ancestors of birds was first suggested in by Thomas Henry Huxley.
After the work of Gerhard Heilmann in the early 20th century, the theory of birds as dinosaur descendants was abandoned in favor of the idea of their being descendants of generalized thecodonts, with the key piece of evidence being caninariojana.com · The Evidence for Endothermy in Dinosaurs: Given: Ecological studies suggest that today's endotherms (mammals and birds) generally outcompete ectotherms in their area.
Given: Dinosaurs were the ancestors of birds. Hypothesis: Since birds are endotherms, dinosaurs must have been caninariojana.com · When the dinosaurs became extinct, plenty of small bird-like dinosaurs disappeared along with giants like Tyrannosaurus and Triceratops.
Why only some of them survived to become modern-day birds caninariojana.com