The family tree
Evolution of dinosaurs?
It is a well known fact that dinosaurs are one of the most heralded examples of evolutionary change from one creature to another. But it seems that just as any other animal that has been catalogued by science, there are large gaps in the story of the history of these creatures. Dinosaur origins is a touchy topic, divided into two contrasting beliefs, incapable of being reconciled.
One side says they evolved from other organisms over millions of years, while the other team says they were created according to their basic kind ( Family or Genus) in creation week around 6,000 years ago. The proponents of evolution say that the gradual process is a proven fact, backed up by numerous scientific facts. While those that oppose the following peoples beliefs challenge their claims and say that scientific evidence actually doesn't support ancient timelines and gradual, random change. Clearly only one view can be correct, but which is it?
*This picture can be viewed better here www.evolutionfairytale.com/images/dino%20family%20tree.gif. Note that only the dark purple lines represent known fossil findings, the other lines all represent theoretical lineages, none of which are based on scientific evidence such as fossils. This means that they don't exist even though they are always presented as established fact.
Most Evolutionary biologists contend that the earliest direct ancestors of dinosaurs were a group of reptiles called Archosaurs. Archosaurs were generally medium to small sized reptiles that are said by many to have first appeared in the late Permian age. They were similar to dinosaurs and had a sprawling gate unlike most "true dinosaurs", they also had an outward facing hip arrangement. Most Archosaurs were believed to be carnivorous, yet some were believed to be herbivorous. It is also believed that most Archosaurs went extinct by the Jurassic. The rest are said to have evolved into the groups forming Dinosaurs, Pterosaurs, Crocodilians and Birds. In addition to being the ancestors of these animal groups, Birds and Crocodilians are often said to be Archosaurs themselves since they are considered to be part of the evolutionary lineage that preceded Archosaurs that evolved into Dinosaurs and Pterosaurs, but have remained unchanged.
Creationists on the other hand reject the ideas and propose their own family history. They generally contend that Archosaurs were just regular species' that fit perfectly into the Creation model and that they are no evidence of Evolution whatsoever. If Archosaurs are so similar to dinosaurs then why aren't they just a type of dinosaur/reptile? Part of the answer is that of worldviews, but another issuse is that taxonomy is a fickle mistress.
Archosaurs are generally regarded as having branched off into Dinosaurs, Pterosaurs, Birds and Crocodilians and fathered all of these Classes and Caldes of animals, which then continued to evolve into new species and branch of into specific subgroups of their appropriate kinds down until the last species we know of from the fossil record. This seems like quite a feat for one type of animal to accomplish considering the overwhelming bounderies of not just genetics, but many fields of science in general such as Biophysics, Astrobiology, Biochemistry, Biomathematics, Cell Biology, Environmental Biology, Neurobiology , Biodiversity, and many others. Alot of problems arise when dealing with Biological Evolution in general, but Archosaurs present some especially evindent challenges in the form of divergence and even the origin of Archosaurs themselves.
*Postosuchus a large Archosaur at about 20 feet long.
If Archosaurs gave rise to dinosaurs, crocodilians, Birds and Pterosaurs, this is an extremely large amount of genetic reshuffling in order to change a lizard-like animal into 4 extremely different body plans. Each of these classes of animals is very biologically specialized to fit Into a certain niche of the environment, be it land, sea or air, depending on the creature in question.
If Archosaurs indeed did evolve into crocodilians as suggested, there are some definite hurdles to overcome and some questions to be answered.
If Archosaurs evolved into crocodilians, why would they keep the sprawling gate unlike the more mammal-like hips and straight up and the down leg arrangements of dinosaurs? And how did they reshape their skull/jaw structure to a longer, flatter design with two sockets that for the front lower teeth to lock into while the jaws are closed? And if Archosaurs were the trunk of the ancestral tree for crocodilians and therefore "more primitive", how could crocodilians have developed a four chambered heart? Let alone stayed alive during the transition.
Archosaurs have much in common with Dinosaurs, in fact many scientists agree that they were indistiguishable in many ways. Which begs the question, were they just dinosaurs themselves? In addition, scientists are split between whether Archosaurs arived before or after the Permian Extinction which is a very large gap of time. And if Archosaurs really did evolve into dinosaurs then how could they survive to live alongside dinosaurs AS Archosaurs? This subject will be discussed further in another area on this site. It seems more likely that some Archosaurs were/are indeed just dinosaurs in reality, however Taxonomy is politics.
As for the belief that Archosaurs evolved into Pterosaurs (and birds according to an increasing number of overzealous believers), it would be impossible for a land dwelling creature to change enough physically to become a creature made for flight. Reshaping and restructuring of bones, reforming of lungs, skull structure and limb digits to allow for flight are all beyond the realm of actual observation and proof and are left up to the imagination like other processes of Macro Evolution. The extending of a digit in order to accomodate for membraneous skin to allow flight is far from explained as there has never been any observation of a non flying creature turning into a creature capable of true flight in literally any way, shape or form. Not to mention that Pterosaurs have never had any ancestors identified, Pterosaurs are only known to have ever been Pterosaurs and have no evolutionary tree. At present Pterosaur origins appear to be, well, a miracle.
These are all but a few serious questions that arise on the issue of dinosaur origin and evolution. It appears from evidence that Archosaurs, just as their supossed decendants, arose as set kinds and not through changing from one kind of animal into another. Such as, Pterosaurs started out as Pterosaurs and Sauropods started as Sauropods, and on and on, The kinds of creatures beginning their existence as their according kind, genetically set in stone. In other words Dinosaurs and their affiliates are descended from Archetypes, not Archosaurs.