Dinosaurs to Birds to Reptiles.

[Thedus]

I've been trying to wrap my head around this for he past week (this was a topic of conversation between my wife and I while on vacation):  How is it that Dinosaurs (presuming they were warm blooded) evolved into modern birds as well as reptiles?  I can understand a warm blooded animal evolving into another warm blooded species... but I'm having a hard time with throwing cold blooded animals into the mix as well.  Especially since modern reptiles would have evolved along side of modern birds.

There is probably a logical explanation to this, I'm just not seeing it.

[SiL]

....since when were dinosaurs said to have evolved into anything but birds?

[Thedus]

Aren't crocodilians the oldest living relative to the dinosaurs?

[SiL]

Crocodilians are crocodilians, surely? Completely different kettle of fish, I thought - They co-existed with the dinosaurs, and from my marginal understanding of reptile classifications, I would've thought they'd have been closer to lizards (what with the leg-structure) than true dinosaurs at any rate.

[SM]

Aren't sharks in the same boat?  ie. They've been around since the dinosaurs (not as in "we're gunna need a bigger boat")?

I think this may be your logical explanation.

"Especially since modern reptiles would have evolved along side of modern birds."

[Neltharion]

It was not all Dinosaurs that evolved into birds. The closest relatives to birds of the Dinosaur world were Therapods, and specifically Dromaeosaurs (Raptors). As they not only had feathers , but were hollow boned(Including the T-Rex, score one for Hunter over Scavenger) and had the general shape of a bird, and after all "Raptor means, Bird of Prey". (Name the movie I quoted for an extra (+) )

Feathers were not evolved for flight, evidence does suggest that as shown here

The Scansoriopterygidae family, who are "Climbing Raptors", all who had feathers, possibly for flight (Not all) but for display, would be the best illustration of an evolution between Dinosaurs and Birds. It is suggested that Epidexipteryx, could not fly due to the lack of bone structure, but had evolved from an ancestor that could indeed fly. And as it is a Dinosaur, it means that its ancestor was a Flying Dinosaur.

The most famous one that suggests evolution from Dinosaurs to Birds is Archaeopteryx.  It is the earliest known "Bird" and shares in common many features with the Dromaeosaurs and the Troodontids(The smartest Dinosaurs). Not only does it have some of the oldest known true feathers, the feathers suggest it was capable of flight.

Also, this is interesting Dinobird


Crocodilians are not Dinosaurs, they are both Reptiles, but there are several visual differences (Duh) and fossil records that show that being Reptile is what connected them.  Yes, in terms of leg structures, Crocodilians are closer to modern Lizards than Dinosaurs.

I do also believe the earliest crocodile evolved before the first known true Dinosaur. Don't quote me on it though.

[Hieronymus]

Dinosaurs did not evolve into reptiles, they evolved from reptiles.

Basically, both mammals and dinosaurs branched off from reptiles.  Then birds branched off from dinosaurs, and the dinosaurs themselves eventually went extinct.

[SiL]

I do also believe the earliest crocodile evolved before the first known true Dinosaur. Don't quote me on it though.

I think the earliest recorded was 98-95 million years ago.

[Dutch90]

I think the earliest recorded was 98-95 million years ago.

The first modern crocodilians (as we know them) emerged around that time, but primitive and now extinct lineages within the clade Crocodylomorpha were already around in the Late Triassic. Crocodilians and dinosaurs are both archosaurs, I'm not entirely sure but they might have a common ancestor.

Oh, and Nel- that's an easy one :

Jurassic Park

[beckmen]

Are you sure it wasn't the third one? Because that was the one that got all gung-ho on the dinobird theory all of the sudden...

Or was it during the dig scene with the kid? Hmmm. These movies need to come out on BD.

[Neltharion]

Dutch got it right.

Dinosaurs did not evolve into reptiles, they evolved from reptiles.

Who said they evolved into Reptiles? They are part of the Reptile family, as are Lizards, Crocodiles, Turtles and the likes.

EDIT: Oh right, its in the Title.

[BishopIII]

 According to most revisionist evolutionary thought, the Class Reptilia doesn't actually exist, at least not in the form that everyone knows it. A Class, by definition, is a cladistic group that has one common ancestor and includes ALL of it's descendents. Therefore, since Reptiles evolved into both Dinosauria and Mammalia, the Class idea of Reptilia fails. Now, the Squamata (lizards and snakes), and Chelonia (turtles) could plausibly be placed into a class, since they are derived from a common reptilian ancestor, and are sufficiently derived from any other evolutionary line, having no non-reptilian descendents. Crocodilomorphs are genetically closer to both of these groups than they are to birds, so they are troublesome with regards to evolutionary placing. I would place the Ornithodira (Dinosaurs and Pterosaurs) into a Class of their own, as they are definitely a Clade, having the unique 'straight-hinge' ankle-joint, whereas all other Archosaurs have an 'L'-shaped joint-line in their ankles, as do Mammals.
  Birds are cladistically Dinosaurs (Manuraptoran Theropods to be precise), as they have no anatomical feature that their ancestors lacked, albeit with some features highly economised and derived. Dinosaurs and crocodiles do share a common ancestry, but this is so far back in the past, way before there were either groups, possibly explaining the genetic divergence. But really, everything has a common ancestor, if you go back far enough.
 As a footnote, there are those who would lump both mammals and birds in with the Reptilia, preferring the names Therapsida and Diapsida (also including Squamata), respectively, and dividing Reptilia into these two main groups. Turtles would form the group Anapsida, if I remember correctly.

[BishopIII]

 And yes, Dinosaurs evolved from Reptiles around 200 million years ago, but as I said, I wouldn't class them as Reptiles themselves, they only seem to superficially resemble reptiles, especially since even non-theropods have been found with integument (a Psittacosaur found in China with a mass of hollow, 'porcupine-quills' on it's tail), which appear to be similar structures to the shorter hollow quills found on the Compsognathid, Sinosauropteryx. This would imply that insulated dinosaurs were more common than we realised! They were more like weird, Pseudomammalian (a term I just made up to describe a nonmammalian mammal equivalent  ) creatures than reptiles!

[Neltharion]

Wall of text Crits You for 10000 Damage (12 Absorbed)
You Die.

[Dutch90]

BishopIII's post made me think of modern paraphyletic classification. Doesn't that basically classify a species under the groups its ancestors belonged too, as well? I.e. humans are technically members of Reptilia and Amphibia as well as Mammalia because mammals descended from reptiles, which descended from amphibians, etc. It makes sense scientifically, but taxonomically it gets kind of chaotic. I guess I've never grown out of the old system where Mammalia, Amphibia, Reptilia, Avia and Pisces were all groups under Chordata and such. Neat and organized.

Whatever happened to Pisces anyway? I read it's no longer a valid group, and there's actually no longer any collective taxonomic grouping for fish like there is for reptiles, birds, mammals and amphibians. I.e. Actinopterygii (ray-finned fish), Sarcopterygii (lobe-finned fish), Chrondrichthyes (cartilaginous fish), etc are all seperate groups, and when looking at a cladogram they don't look any more related than Mammalia and Reptilia.

My knowledge here is rusty, though. When I was a kid I read through tons of books about animals, but classification never got my full attention. I just knew the basics, which may no longer be up to date.