Carroll, Lewis L., "Problems of the Origin of Reptiles," Biological Reviews of the Cambridge Philosophical Society, vol. 44 (1969).
p. 393
"Unfortunately not a single specimen of an appropriate reptilian ancestor
is known prior to the appearance of true reptiles. The absence of such ancestral
forms leaves many problems of the amphibian-reptilian transition
unanswered."
The Origin of Reptiles
We find the same situation concerning the origin of reptiles that is found with amphibians—the abrupt appearance of each basic type with no transitional forms to provide the expected evolutionary links and to reveal the evolutionary pathways leading to each basic kind.
Reptiles are included with the class Reptilia. Reptiles, birds, and mammals are included in the assemblage, Amniota. The amniotes, unlike amphibians, can lay their eggs in environments free of water or moist surroundings because they produce eggs that are equipped with extraembryonic membranes. The amniotic egg of the reptile is vastly more complex than the egg of an amphibian. The eggs of reptiles contain a membrane, the amnion, which provides a sac within which the developing embryo floats. The allantois provides a reservoir in which waste products accumulate, and there is a yolk sac containing the food supply for the developing embryo. The whole is surrounded by a shell strong enough to protect the contents of the egg, but at the same time porous enough to allow the exchange of gases with the environment, the intake of oxygen, and the passage out of carbon dioxide. Evolutionists must imagine that this utterly complex system somehow evolved, step by step, via a series of random, undirected, accidental changes in the genetic system of an amphibian. These changes had to be accompanied by the necessary alterations in the reproductive system of the proto-reptile, also produced by purely accidental changes in the genetic system of the ancestral amphibian. During the transition each intermediate stage had to be fully functional and possess advantages over the preceding stage that enabled it to outcompete and thus replace the preceding stage. Many of the vital structures, such as the amniotic cavity and the amnion, has to be produced de novo in the reptile, since there are no homologous structures in the amphibian from which they could have been derived. It is likely that no evolutionist would even try to imagine the evolutionary pathway taken and the intermediate stages involved in the evolutionary origin of the amniotic egg.
Evolutionists believe that there exists in certain amphibians and reptiles a number of characteristics that indicate a link between reptiles and amphibians. For example, Colbert and Morales states:
The mixture of amphibian and reptilian characters seen in Seymouria is indicative of the gradual transition that took place between the two classes during the evolution of the vertebrates.5-27
Any attempt to use Seymouria as suggestive of an intermediate between reptiles and amphibians immediately encounters serious contradictions. Those creatures suggested as the earliest known reptiles, Hylonomus and Paleothyris, are found in Lower Pennsylvanian rocks (about 330-315 million years before present on the evolutionary time scale) and the Middle Pennsylvanian rocks (about 310-315 million years), respectively. Fossils of Seymouria are found in Lower Permian rocks, dated at about 280 million years, or at least 25 to 35 million years too late to be ancestral to reptiles.
Furthermore, there are other serious problems in attempts to link Seymouria to reptiles. Romer asks the question, "Did Seymouria lay its eggs frog fashion, in the water, or produce shelled, land-laid eggs of amniote type?" He goes onto say that the answer must be derived by studying the broad group of creatures included within the order Seymouriamorpha. He cites Kotlassia, which
… show in flattened skulls, relatively feeble ossification of the skeletons, and other features, a series of regressive changes associated in typical amphibians with a reversion to permanent water-dwelling existence. Again, there have been discovered in the early Permian of Moravia gill-bearing larvae of Discosauriscus similar to the "branchiosaur" larvae of rhachitomes, and indicating that in reproductive features the seymouriamorphs were definitely amphibians.5-28
Diadectes is often cited as being very close to the dividing line between amphibians and reptiles. It is also a most improbable candidate, however. It is about 30 million years too late on the evolutionary time scale to be ancestral to reptiles, and it was a large, clumsy creature, about ten feet in length, in contrast to the "primitive" reptiles, which were very small, with bodies from snout to the base of the tail only about four inches in length.
Although a number of characteristics in Seymouria and Diadectes are cited as revealing similarities to Hylonomus, Paleothyris, and other "early" reptiles, there is an unbridged gap between amphibians and reptiles. Here are a few examples that establish that reptiles were reptiles at the start, with no transitional forms linking them to any so-called ancestral amphibians. Carroll states (all quotes are from note 5-1):
The earliest known amniotes are immediately recognizable as members of this assemblage because of similarities of their skeleton to those of primitive living lizards (p. 193).
The most significant feature of the palate in early amniotes is the presence of a transverse flange on the pterygoid … In modern lizards, the transverse flange of the pterygoid serves as the origin of one of the largest of the jaw-closing muscles, the pterygoideus … There is little evidence of the existence of a large pteryoideus muscle in any primitive amphibian (p. 194).
The general structure of the braincase of early amniotes resembles that of modern lizards (p. 195).
The postcranial skeleton of early amniotes generally resemble that of the primitive living reptile Spenodon (p. 195).
In contrast [to early labyrinthodont amphibians], the early amniotes closely resemble primitive living lizards in their small body size and proportionately small skull. The structure of the teeth and probable arrangement of the jaw musculature in early amniotes resemble those of living lizards that feed almost exclusively on insects and other small arthropods (p. 198).
The skeletal anatomy of protorothyrids [Hylonomus and Paleothyris are placed in the family Protorothyridae] remains relatively constant from the Lower Pennsylvanian through the Lower Permian. During this time, a series of other amniote groups appear in the fossil record. Each may have independently evolved from the proterothyrid pattern. None show close relationships with one another (p. 201).
The early amniotes are sufficiently distinct from all Paleozoic amphibians that their specific ancestry has not been established (p. 198).
The last statement just quoted establishes beyond doubt that transitional forms between amphibians and reptiles do not exist. If they had been found, there would be no doubt concerning which amphibian gave rise to reptiles.
Just where transitional forms are most critically needed, as just described above, they are always absent. That will be abundantly illustrated as the origin of distinctly different types of reptiles is documented. These widely divergent groups of reptiles include the flying reptiles, the marine reptiles, the gliding reptiles, the snakes, and the turtles.
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