What are reptiles designed for?


If evolution is correct, the ancestral reptile body plan could be modified for a variety of different lifestyles.


If the creationism model is correct, the variation within groups should not compare to the variation required so that one kind could evolve from another.


If intelligent design is correct, it is not expcted that an intelligent design would need to be continually reworked to produce greatly divergent final forms.

Reptiles share a number of features which separate them from other vertebrates. Are reptiles intelligently designed? Given the great variation among reptiles, it is difficult to imagine what reptiles could be designed for.

For example, reptiles include the largest of all terrestrial herbivores, the largest of all terrestrial carnivores, the largest aquatic carnivores, and the largest flying vertebrates. Instead of being designed specifically for a specific lifestyle, it appears that reptiles were able to modify their ancestral structures to adapt to a variety of ecological niches.



Not only are there enormous variations within the broad group of reptiles, there are significant variations within individual reptilian subgroups. For example, theropod dinosaurs vary in size from bird-sized species to giant predators fifty feet long. Some possessed nasal horns, brow horns, and crests. A variety of tooth forms evolved. The bird mimic theropods included forms which possessed 200 small teeth (the greatest number among theropods) and others which were toothless. Segnosaur teeth might have adapted them to feed on plant material. A number of separate lineages evolved switchblade foot claws. Baryonx might have been quadrupedal, unlike other members of the group.
teeth skull



Prosauropods include bipedal, quadrupedal and intermediate forms. Sauropods varied in the size (some reaching more than 100 feet in length), the length of the necks (including some short-necked forms), and the presence of armor.




Ceratopsians varied in their size (including some very small forms), locomotion (including bipedal, quadrupedal and intermediate forms) and the presence/absence of horns and frills.



The armor of armored dinosaurs varied from small osteoderms to large plates, fused masses of bone, tail spikes and tail clubs.



Many of these anatomical structures were not unique to dinosaurs. For example, greatly elongated necks evolved in a number of completely separate lineages. Among late Paleozoic protorosaurs, neck length increased in the lineage leading to Tanystropheus (with Protorosaurus and Araeoscelis representing intermediate stages of elongation). Many marine forms (especially plesiosaurs) also elongated their necks. While plesiosaurs of the family Plesiosauridae possessed a neck with 22 to 44 vertebrae, those of the family Elasmosauridae possessed 42-76 cervical vertebrae.


Armor was also known among diverse lineages. Among primitive archosaurs, species of the families Euparkeriidae and Phytosauridae possessed armor. Extensive armor covered both the dorsal and ventral sides of the body in species of the families Aetosauridae and Stagonolepidae. Armor was also known in pareiasaurs and extinct lizards. Of the four families of Placodonts, the family Helveticosauridae lacked armor, species of the family Placodontidae possessed little or no armor, The family Placochelyidae possessed a carapace of dermal bone, and the family Henodontidae possessed a bony plastron in addition to the bony carapace.




Some reptiles are adapted for a terrestrial lifestyle. This would include most lizards and snakes, most turtles, and most of the fossil reptiles including dinosaurs. However, there are many species which adapted to an arboreal lifestyle (lizards, snakes, some theropod dinosaurs) and burrowing (some lizards, snakes, and other reptiles).
Some lineages took to the air as gliders such as the coelurosauravids among the primitive diapsids, the extinct lizard Kuehnosaurus, the modern lizard Draco, and some modern snakes. Some actually developed the ability to fly such as Longisquama, pterosaurs, dinosaur ancestors of birds, and possibly additional lineages of dinosaurs as well (such as Microraptor).


Some reptiles developed the ability to run bipedally such as some modern lizards (such as basilisks), extinct lizards, thecodonts, and crocodiles.