Chapter 5 Patterns in Evolution | Retention of Inefficiency | Retention of Ancestral Traits Despite Change in Habitat | Snakes | Birds | Pterosaurs | Pinnipeds | Turtles | Lepospondyls | Moss | Ichthyosaurs | Sauropterygians | Bats | Recapitulation

Retention of Inefficiency

Evolution happens gradually.  We can know this because it takes evolution a long time to delete inefficiencies from species that are less than perfectly adapted to their environments.  Two examples from the fossil record are whales and horses.  These two examples provide powerful testimonies on behalf of Darwin's opinion that evolution happens gradually.

The primitive whale Basilosaurus retained small hind legs even 10 million years after its ancestors had crawled from land into the sea.  Basilosaurus did not use and did not need these legs, yet still had them.

The ancestors of the whales were probably the mesonychids – four-legged land-dwelling carnivorous mammals.  There are several genera of mesonychids that lived in North America and in Asia around the same time, 1 such as the 62 million year old Ankalagon from New Mexico.  About 48 million years ago, we find two species that represent intermediaries between the mesonychids and the whales - namely Pakicetus and Ambulocetus.  Although they had adopted some aquatic traits,they were still partially terrestrial, walking on four feet, and had not yet achieved the body of a whale.  10 million years later, the primitive whale Basilosaurus still retained small hind limbs, but was otherwise a purely aquatic whale.  Thus, whales provide a good example of how evolution happened gradually over millions of years.

Another example is the horse.  Primitive horses from 50 million years ago had four toes on the front foot and three on the back.  They gradually lost all but one enlarged toe on each foot.  Second, horse teeth have gradually improved over time.  At first, their teeth were low crowned and ill-adapted for tough grasses, but today, their teeth are high crowned and well adapted for grass.  Third, the earliest horses were extremely small, no bigger than a mid-sized dog, which made them easy prey.  Only over tens of millions of years did they become large enough to deter most predators.   

Unlike the Cambrian Explosion, horse evolution was a long time in coming.  It took horses tens of millions of years to overcome key inefficiencies in their feet, teeth, and size.  Even after 50 million years, their face and body shape still look very similar to the way they did back then. 

From a broad perspective, horse evolution can be considered as happening gradually.  Yet at finer resolution, Gould asserted that each species is actually "well marked and static over millions of years," contradicting the "myth about horse species as gradualistically-varying parts of a continuum." 2  Thus, in Gould's view, horse evolution happened as a procession of steps, which in the big picture gradually ascended; yet each step by itself was not gradual, but a leap.

The transformation from fish fins to feet is thought so difficult to achieve that it only happened once. 3  Estimates for the time it took to complete the transition, start to finish, are limited to 15 million years or less.  This is because 15 million years is the distance from the earliest Frasnian to the latest Famennian, i.e. – from 378-363 million years ago.  Rich fossil beds display abundant flesh-finned fish such as Eusthenopteron and Panderichthys in the earliest Frasnian, but no legged-animals; yet 15 million years later in the late Famennian, fully developed legged-animals are abundant.  Leading tetrapod expert Clack estimated that the transition happened in less than 5-10 million years, because footprints and trace fossils of legged animals Obruchevichthys and Elginerpeton appear in the late Frasnian, 5 million years before the well-defined forms Acanthostega and Ichthyostega become plentiful. 4  Others see a slightly longer transition, from 9 million years 5 to 12-15 million years. 6  Hence, by all estimates, fish with fins transformed into land-walking creatures with well-defined and fully functional legs in 5 to 15 million years or less.  The possibility that it happened in an even shorter time is still open, as a flood of freshly discovered fossil tetrapods are still turning up.  The first important transformation from fins to feet is noticed in Panderichthys, the most primitive fossil form to adapt its arm bone into an immobile platform to support the body. 7

This 5 to 15 million years is a short period of time when compared to the amount of time it took for natural selection to perfect legs.  From the first appearance of legs in the fossil record, until the time legs evolved into efficient running machines, is about 135 million years.  The first animals with legs were extremely slow and cumbersome on land.  This was because legs were not positioned directly under the weight of the body, but were flanged out to the sides.  Thus, the earliest four-legged animals could only waddle.

Also, legs were rather short for a long period of time, failing to lift the head much above the ground.  If a species could have evolved the ability to grow long legs, it would have proven a distinct advantage, for long legs would have enabled that species to eat herbs forbidden to animals of a lower height.  As it was, legged-vertebrates did not even evolve the ability to eat plants at all until the latter Carboniferous.  One would think, since they grew legs in less than 15 million years, they should have evolved a digestive system to cope with plants in less than 40 million years, but such was not the case.  Height could have also protected animals' necks from the bite of predators.  Under these selective pressures, we might expect that tall animals should have evolved fairly quickly.  After all, if it only took 5 or 15 million years for evolution to turn a fish fin into a leg, it should not take much longer for evolution to make the leg more efficient.  Yet this did not happen.  Land animals stayed low to the ground, even the largest of them barely able to lift their heads much more than a couple feet off the forest floor.  Their legs flanged out to the sides, inefficiently supporting their body weight, and slowing them down. 

These inefficiencies were retained for about 80 million years, at which time modest improvements were made by the mammal-like therapsids.  Yet the therapsids' legs were still flanged out to the side, and they failed to reach the height necessary to eat herbs high in the trees.

The archosaurs achieved a breakthrough about 250 million years ago when they attained the ability to place their weight directly under their legs, rather than having their legs splayed out to the sides.  The descendents of the archosaurs, the dinosaurs, perfected this ability with the evolution of a socket joint in the hip capable of both swift speeds and the ability to stand on just two feet.  They also added length to their legs for greater height.  Hence, it was not until the time of the dinosaurs that legs finally reached their full potential in terms of speed, strength, height, and efficiency.  The first dinosaurs evolved about 230 million years ago – roughly 135 million years after legs first evolved.  Thus, despite their comparatively rapid evolution from fish fins, legs retained grave inefficiencies for 135 million years.

The paradox is inconsistency in the rates of evolutionary progress.  It took only 5 to 15 million years for fish fins to turn into legs, yet it took another 135 million years for unsteady waddling legs to become sure-footed fast running legs.  The greater morphological change occurred in the shorter period of time, and the lesser morphological change occurred in the longer period of time.  If natural selection required a whopping 135 million years to make adjustments to an existing form, then why did it require only 5 or 15 million years to invent a radically different form?  It is a matter of a strange discrepancy in the speed of evolutionary change.  If natural selection works only slowly over time, as genetics suggests, then it must be asked what force besides natural selection causes accelerations in the amount of evolutionary change? 

Retention of Ancestral Traits Despite Change of Habitat

During the Cretaceous period, certain lizards invaded the ocean and became sea monsters of enormous size.  Called mosasaurs, these monster lizards ruled the deep from 90 to 65 million years ago, 8 and they left an exceptionally complete fossil record over their 27 million year tenure. 9  Carroll and deBraga have argued for the gradual evolution of the mosasaurs over more than 60 million years, from the anguimorphs to aigialosaurs to mosasaurs, although the earlier parts of the transition are somewhat wanting in the fossil record. 10 

Despite 27 million years of dominating the oceans, the mosasaurs did not become radically different from their terrestrial lizard ancestors.  Both inside and outside of the water, they were always more akin to lizards than to any fish or other marine reptile.  The mosasaurs retained their lizard-like appearance.  They did not develop caudal tails or dorsal fins like fish.  Their skull shape remained flat and v-shaped across time, both as terrestrial lizards and as aquatic reptiles.  They were long and slender, both as lizards and as mosasaurs.  They made certain adaptations to aquatic life, including broader tails for swimming and shorter limbs, but their tails were unlike those of fish, and the digits on their limbs retained a distinctly lizard-like skeletal structure.  

The success of the mosasaurs is a testimony to an oft overlooked evolutionary pattern – namely, it is not necessary for a lineage to become radically different from its ancestors in order for it to succeed in a new habitat.  Mosasaurs did not need to become fish in order to succeed in the ocean.  They did fine just being lizards, and they even outcompeted the fish as successful predators. 

Applying this to the Cambrian Explosion, one might ponder why so many different forms suddenly emerged in the Cambrian, for they did not need to diverge into such an array of various forms to fill new habitats.  Cambrian life could have retained the same basic structure of the most primitive phyla, cnidarians and sponges, and made only small adaptations over time to attain the full potential of those phyla.  There was no adaptive necessity for radically different structures to evolve in the Cambrian as they did.

Besides mosasaurs, other terrestrial creatures have invaded the seas,  including whales, sea cows, sea lions, ichthyosaurs, plesiosaurs, and turtles.  Each of these comes from a lineage distinctly different from the others, which was originally terrestrial, and each retains many features of its terrestrial ancestors.  They have not become fish-like, nor have they converged to become like each other.  Rather, each has retained its unique structure from when it used to be terrestrial, and this remains true down through the aeons.  Nor did any of them develop the ability to breathe underwater as fish do, though it would be an evolutionary advantage for them to do so.  Why has evolution proved incapable of allowing sea faring reptiles and mammals to breathe under water as fish do?

When multiple lineages evolve to fill the same habitat, there is no rule that they must become similar to each other.  Rather, they retain the characters of their ancestors.  In Carboniferous times, giant dragonflies filled the skies.  In Mesozoic times, flying reptiles called pterosaurs overtook the dragonflies.  Now, the air is dominated by birds and bats.  Yet each of these four – dragonflies, pterosaurs, birds, and bats – are entirely different from each other in terms of body structure and flight propulsion.  If there were a certain type of wing best suited for flight, then we should expect to see these four converge toward a common type of wing.  Yet this is not the case.  For 400 million years, the dragonflies have kept essentially the same body plan, having no bony digits to support their wings.  In contrast, pterosaur wings were supported by a single very long bony digit on the front edge of the wing.  Yet birds' digits are short and contained deep inside the wing.  Also, birds are the only one of the four to employ feathers in flight.  If feathers are easily derived from scales, as some believe, then why were pterosaur wings so lacking in them?  Bats, for their part, exhibit a wing structure entirely different from the first three, having four very long bony digits to support their wings. 

Therefore, natural selection does not force species to evolve the highest and best structure.  For every habitat and niche, there are a variety of structures capable of succeeding in it.  Hence, species tend to retain the structures of their ancestors, rather than develop entirely new structures.  When an ancestral structure proves inadequate, it is modified, not immediately discarded for a new structure.  Thus, animals are not perfectly adapted to their habitats.  They just make do with what they have, gradually tweaking it through the aeons to make it workable.

Radically different body plans are not necessarily required for species to adapt to various ecological niches.  Rather, the same body plan can be used for a very broad variety of environments.  Arthropods have taken to the air as insects, yet they also crawl on the ground, and dwell in the ocean as lobsters.  Wherever they roam, they retain the same essential characters of arthropods.  Mammals have adapted to life in the trees, on the ground, in the ground, on the water, in the water, and in the skies – yet they retain the same characters in terms of having fur and giving birth to live young.  Why, then, have so many different forms emerged?  One or two phyla could have easily filled the planet.  As far as natural selection is concerned, the multiplicity of phyla generated in the Cambrian Explosion was not necessary.

Snakes

Snakes evolved from four-legged lizards.  They lost their legs when they began to slither.  A very large number of intermediary forms in the fossil record provide evidence for this.  Coniasaurus was a snake-like reptile that had an elongated neck, torso, and tail, but also had four short limbs. 11  Several fossils yield a range of dates from the early Cenomanian to the mid Santonian, 12 which is from 99.6 to 84.5 million years ago.  Haasiophis was an advanced snake that had small yet distinct hind legs.  It is from the early Cenomanian, corresponding to about 99 to 95 million years ago. 13  Pachyrhachis was an advanced snake from the Cenomanian that had well-developed hind legs, but no front legs. 14  Podophis was another advanced snake with legs from the same time. 15          

There are also a number of snake-like forms with limbs that lived in aquatic environments.  The sea monster lizards, the mosasaurs, are considered to be a relative of snakes, on account of shared characters such as thecodont tooth attachment, 16 elongated body form, skull similarities, reduced limb size, a second row of teeth on the upper palate, and kinetic jaws (meaning the jaw can crack open like a break-action shotgun to enlarge the mouth).  Another marine squamate, Adriosaurus, lived 95 million years ago.  It was similar to a snake in that it had a long and narrow trunk and tail, yet it had very small front legs and good-sized hind legs. 17  Dolichosaurus was a four-legged marine reptile with small front legs, a break action kinetic jaw, and a very long snake-like neck and tail.  Its legs were apparently so small that they were useless, and were purely vestigial. 18

These half-snake half-lizard intermediaries congregate in the vicinity of 99 to 85 million years ago.  Therefore, one might assume that full-fledged snakes evolved sometime thereafter, perhaps 80 to 70 million years ago.  But this assumption is inaccurate. 

Sound science, both from the fossil record and from molecular DNA, indicates that full-fledged snakes evolved before these intermediaries existed.  According to molecular evidence, snakes arose approximately 125 million years ago. 19  According to the fossil record, the earliest indisputable snakes occur in the latter half of the Albian, which is about 106-99 million years ago. 20  Thus, snakes were already up and running, or down and slithering, as it were, before these intermediaries with legs arrived in the Cenomanian.   

Hence, despite the fact that the snakes with legs appear to be good intermediaries, they could not have been the true ancestors of modern snakes.  Instead, they were the descendents of a common ancestor they shared with snakes, i.e. – they were snakes' sister taxa. 

The Cenomanian, some 99-93 million years ago, is the era when snakes first became common.  Far from being primitive, they were already well-advanced, even though they were very early.  From the beginning, snakes were macrostomatan, that is, they possessed a unique skull and muscular structure in the head that allowed them to swallow prey bigger than their own diameter.  In this character, they appear to have skipped over the scolecophidea and alethinophidea branches of the order serpentes, which, according to molecular DNA analysis, should have come before them as evolutionary steps toward the more advanced macrostomatan form. 21  It is strange that snakes would reach such an advanced form so early, as Rage and Escuillies said,

"The three hind-limbed snakes have a macrostomate skull; but in existing snakes this character appears only in forms considered to be the most "advanced," the macrostomata, a priori, this structure should be derived… the presence of hind legs and macrostomate structure, poses a serious problem." 22

Reippel et al commented in like manner,

"With Haasiophis, Pachyrhachis, and Podophis representing macrostomatan snakes, the question of the sister-group relationships of snakes within Squamata, or of snake '"origins," remains unresolved.  Nevertheless, the presence of snakes with macrostomatan characters at 95 Ma (million years ago) indicates that a series of cladogenetic events leading to the major extant groups of snakes occurred prior to the mid-Cretaceous." 23 

This means that snakes had already diverged and become advanced prior to 99 million years ago.  Therefore, a significant amount of snake evolution must have occurred that has not been preserved in the fossil record.  Either this evolution occurred tens of millions of years beforehand in the early Cretaceous, as Darwinists would prefer; or, it occurred so quickly that the fossils were not preserved.  The latter accords better with the actual fossil data, because the fossils don't go back beyond the Albian.

The problematic nature of snake origins has also led to a debate on aquatic versus terrestrial origins.  Caldwell suggested that "snakes, mosasauroids, dolichosaurs, and coniasaurs may have a common aquatic ancestor." 24  But Wiens et al maintained that snakes evolved from terrestrial burrowing reptiles, 25 because the two most basal lineages of snakes are burrowers – the scolecophidians and the annelids. 26

It is a problematic pattern often observed in the fossil record.  When we reach back in time to the beginnings of a new life form, we often find a woefully incomplete or non-existent record for how that life form came about.  There are three possible explanations for this:  

1) Either the fossil record is poorly preserved, or

2) Some intelligent being suddenly creates new forms out of thin air, or

3) New forms evolve so quickly that there is not enough time for the missing links to leave fossils. 

Applied to snakes, the problem with the first hypothesis is that the fossil record is not poorly preserved.  As demonstrated above, the fossil record adequately recorded a host of intermediary forms.  It has also provided us with innumerable specimens of lizards, mosasaurs, full-fledged snakes, etc.  Surely, if snakes evolved gradually over millions of years, we should expect to find intermediaries that predate the appearance of advanced snakes 95 million years ago. 

The problem with the second hypothesis is that intermediary forms do exist.  If God created snakes out of thin air, then why do we see so many snake-like forms with reduced limbs in the fossil record?  Moreover, traces of the rear legs are found in some snakes even to this day.  Why would a Creator God make snakes with legs they don't need?

Only the third hypothesis makes sense.  If snakes evolved rapidly, then the missing links did not exist long enough to leave fossils.   Nevertheless, the missing links did have children, some of which still retained sizeable legs.  It is these descendents of missing links that are found so frequently in the fossil record.  Although the intermediaries with reduced limbs occur too late to be the missing links themselves, they are the right age to be the descendents of the missing links.  Thus, when snakes evolved from lizards, their transformation happened so quickly that the missing links were not preserved, yet the children of those missing links show up millions of years after the transformation, as contemporaries of the more advanced forms.

The loss of all traces of legs in snakes is known to occur very slowly over time.  For example the annielline and anguine snakes are known from 50 million years ago, yet still retain the pectoral girdle bones. 27  Even after 100 million years, natural selection has failed to complete the transition, for some snakes today still possess vestigial elements of hind limbs.  The traces of vestigial legs in snakes even after 100 million years, is a testimony to how slow and inefficient natural selection actually is. 

It appears as though there are two types of evolution.  One type generated a massive transformation from lizards to snakes in just a short time.  The other type has been gradually trying to tidy up the last vestigial remnants of that transformation – a process it still has not completed even after 100 million years.  One type of evolution is rapid.  The other type is gradual.  Gradual evolution has accomplished less in 100 million years than rapid evolution accomplished in a much shorter period of time. 

The best explanation for this is that there are two separate mechanisms that bring about evolution – the gradual mechanism being natural selection, as Darwin described it, and the rapid mechanism being some other kind of force.

Birds

Birds and reptiles have a lot in common.  Similarities in their bones, digital claws, red blood cells, kidneys, penis, together with the reptilian appearance of bird embryos all speak to a common ancestor. 28  A high calcium diet even causes birds to develop reptilian ankle bones. 29

Birds have even more in common with a certain type of reptile – the theropod dinosaurs.  They share the following characters:  fused clavicles, feet with three claws pointing forward and one backward, partially fused metatarsals, and a second set of ribs covering the front of the torso. 30  The earliest bird, Archaeopteryx, even had three fingers with claws coming out the top of its wing, and it had teeth in its mouth instead of a toothless beak.  Theropod dinosaurs also had three fingers, all with claws, and sharp teeth in their mouths.

One theropod in particular, Compsognathus, is often placed in museums next to the earliest bird, Archaeopteryx, to show their similarity.  At first glance, they look similar because they are both about the size of a chicken.  However, there are a number of substantial differences between Archaeopteryx and Compsognathus.  Archaeopteryx had a longer femur, thinner leg bones, and its tail vertebrae are of a different type than those of Compsognathus, having exchanged dinosaur features for bird-like features. 31  Other characters of Archaeopteryx are distinctly more bird-like than dinosaur-like, including a larger brain size, the closeness of its teeth, the lack of dental serration, the nature of its shoulder girdle, its caudal maxillary sinus, fewer bones in the tail, its reduced prezygapophyses, its elongated prenarial, the break up of its postorbital bar, and the relationship between its caudal and columellar parts. 32

Archaeopteryx had full wings and tail feathers capable of flight.  In contrast, Compsognathus had no wings at all, and does not appear to have had any feathers – not even a few small ones on the skin for warmth.  In another gross morphological difference, Archaeopteryx possessed an ornithischian hip, wherein the pubis and the ischium both are positioned toward the posterior, unlike the saurischian hip of Compsognathus, with its forward placement of the pubis, as in all theropods.  On paper, this sounds obscure, but it is significant because if it weren't for other features, an ornithischian hip would normally make the bird more related to completely different looking dinosaurs such as the horned Triceratops and the plated Stegosaurus.

So even though Compsognathus looks superficially similar to Archaeopteryx, it is actually a rather poor candidate for a "missing link."  We should look to other candidates.

The coelurosaurian raptor dinosaurs make a better intermediary.  Unlike Compsognathus, many of the raptors had feathers, they had a stiffened tail, and their pubis was midway between the saurischian position and the ornithischian position.  Other characters shared with birds include a wishbone, birdlike feet, a carpus bone in the wrist, the social behavior of traveling in packs/flocks, and the presence of longer arms than those of other dinosaurs. 

A wealth of such raptors has been uncovered from the Yixian Formation in Asia.  However, the age of the Yixian Formation is about 125 to 120 million years ago, 33 which presents a problem, because the first bird Archaeopteryx is known from a half-dozen specimens that are 25 to 30 million years older – found in the beginning of the Kimmeridgian of Bavaria, dating to 155 million years ago in the late Jurassic.  Thus, the feathered raptors of the Yixian Formation are too young to be the missing link between birds and dinosaurs.  Even though the feathered dinosaurs from the Yixian Formation might be related to the birds, they cannot be direct ancestors.  As Martin states,

"The small coelurosaurian dinosaurs related to Archaeopteryx all occur in the fossil record after Archaeopteryx and so cannot be directly ancestral." 34

The dilemma concerning the origin of birds is similar to that of the snakes.  Raptors are to the birds what reduced-limbed lizards are to the snakes – an intermediary form that would be a good example of a missing link, except that it arrives too late in the fossil record to be a missing link.  Because they are intermediaries, they give evidence for the theory of descent in a general sense, yet because of their timing in the fossil record, they fail to provide true evidence for a gradual transition between forms over long time frames.  We are left with the reality of rapid evolution – the sudden evolution of new forms.  Raptors were evidently the descendents of missing links that evolved so quickly that they left little trace in the fossil record. Luckily, there is at least some hope for finding a missing link.  A few raptor-like dinosaurs can be dated to around 160 to 165 million years ago, which is about 5 to 10 million years prior to Archaeopteryx.  Hence, it is still possible that the perfect intermediary might be discovered. 

After Archaeopteryx, early birds retained certain reptilian characters for a long time, such as toothed mouths instead of the typical beaks of modern birds.  Their transition into truly modern forms was a long time in coming, and did not reach fruition until the Eocene and Oligocene – long after the dinosaurs became extinct.  Thus, the amount of time it took natural selection to perfect the new form was much longer than the time it took rapid evolution to build the basic structure of the new form.  As with the snakes, it appears that there are two mechanisms for evolution in play – rapid evolution of new forms by means of an unknown force, followed by gradual evolution of existing forms by means of natural selection.

Pterosaurs

Pterosaurs were winged reptiles that ruled the skies during the time of the dinosaurs.  They first appear in the fossil record near the Carnian-Norian boundary, soon after the dinosaurs made their debut, and they went extinct during the same catastrophe that the dinosaurs did.  They were also closely related to dinosaurs. 

Rapid evolution best describes the origins of the pterosaurs.  According to Haines and Chambers,

"In particular, pterosaurs suddenly appear in the fossil record as highly specialized fliers with no clear intermediates before them." 35 

They go from no representation in the fossil record to suddenly very adequate representation in the Norian, and quickly radiate into several new species to fill various ecological niches.  The earliest among them is Eudimorphodon, which is found in various rocks of early Norian age, such as the Fleming Fjord formation. 36  Moreover, one pterosaur feature that was at one time considered advanced, namely the head crests of the later pterodactyls, is now known from a fossil of Norian age, 37 thus demonstrating that the pterosaurs achieved advanced features at the very beginning of their history. 

The fundamental features of the pterosaur body plan remained constant from their earliest beginnings to their ultimate demise.  They had small bodies, lightweight bones, sharp teeth, long mouths, and long arms.  At the end of their arms, they possessed four fingers.  The first three fingers terminated in three short claws, which stuck out at the front of the wing and could be used for crawling on the ground when not in flight.  The fourth finger was extremely long by comparison, often extending several feet away from the body.  The bulk of the wing was supported on this fourth finger.  The wing was a lightweight flap stretching from the fourth finger to the back leg.  This body plan continued unchanged for all of their 160 million year tenure. 

The most plausible ancestor the fossil record can provide is Scleromochlus of the Lossiemouth Formation.  If Scleromochlus is the ancestor of the pterosaurs, it would mean that pterosaurs accomplished a tremendous amount of evolution very quickly across the Carnian-Norian boundary.  Scleromochlus did not have even the beginnings of wings.  The fourth finger, so greatly elongated in pterosaurs to support the wings, in Scleromochlus is no more elongated than the other fingers.  Scleromochlus also had short arms and long legs, the opposite of pterosaurs.  Benton even concluded that Scleromochlus was no more related to pterosaurs than to dinosaurs, but had split from both of them shortly before their most recent common ancestor. 38  Hence, the morphological differences between Scleromochlus and the earliest pterosaurs are great, and require that a tremendous amount of evolution must have occurred in a short time for them to have had been ancestor and descendent. 

Then, there is the problem of whether Scleromochlus really predates their supposed descendents, the pterosaurs.  There is some question as to whether the allegedly late Carnian strata of Scotland's Lossiemouth Sandstone is really Carnian or whether it is actually early Norian. 39  If Norian, the supposed ancestor is a contemporary of the pterosaurs, and therefore unlikely to be an ancestor.  To add fuel to the fire, there is also some question over whether the pterosaurs first appear in the Norian or in the late Carnian.  A pterosaur jawbone has been reported from the Dockum Group of Texas, hence plausibly putting the first pterosaurs in the Carnian. 40  If this is correct, then it makes the pterosaurs at least contemporary with, if not before, their supposed ancestor Scleromochlus.  In any case, Scleromochlus cannot support the idea that pterosaurs evolved gradually, because it did not arrive in the fossil record substantially beforehand. 

Thus, the search for a pterosaur ancestor is elusive at best, both for morphological reasons and for stratigraphical reasons.  The most that can be said is that they arose suddenly, without intermediaries, and that the closest thing to their ancestor is essentially their contemporary.  Hence, pterosaur origins point to an instance of rapid evolution, whereby evolutionary change happened so fast that no fossil intermediaries were preserved.

The evidence does not, however, point to the spontaneous creation of the pterosaurs by God.  It is highly unlikely God created them perfectly, for the earliest among them were lacking shorter tails and toothless mouths – two features that are proved advantageous adaptations to an aerial lifestyle, both in pterosaurs and in birds, and the former in bats as well.  If God is perfect, it stands to reason that he creates new forms perfectly, but pterosaur tails and teeth were far from perfect when they first took to the skies. 

It took 40 million years to shorten the tail of pterosaurs such that by the latter Jurassic they evolved into the very short-tailed pterodactyls.  Yet strangely it only took a fraction of this time for pterosaurs to get wings with full-powered flight.   Their primal point of origin, their morph into a new and completely different body structure at the base of their lineage, is shrouded in mystery, and seems to have happened so rapidly that it did not leave a trace in the fossil record.  Hence, pterosaur evolution represents a two step process – rapid evolution of a new form, followed by small improvements to that form over time.   

Pinnipeds

Seals, sea lions, and walruses are all part of the same lineage called pinnipeds.  According to molecular DNA evidence, their nearest kin are skunks and weasels. 41 42  However, their earliest fossils look nothing like skunks and weasels.  Instead, they look much like they do today.  The earliest among them is Enaliarctos.  Some of the features it has in common with modern pinnipeds include flippers instead of feet, equal length elongated toes, short femur and humerus bones, general size, and overall appearance.  According to Berta et al,

"Enaliarctos documents an early, yet complete, stage in the acquisition of features associated with aquatic locomotion in pinnipeds."

Yet Berta et al also note the olecranon process and the number of lumbar vertebrae are different from later pinnipeds, and state that Enaliarctos is therefore intermediate between terrestrial animals and later pinnipeds. 43  Enaliarctos is the best the fossil record can provide for an intermediary between terrestrial land mammals and pinnipeds.

Enaliarctos shows some affinity to bears, 44 and it was widely believed for a long time that pinnipeds' closest relatives were bears.  The molecular DNA evidence indicates that indeed bears are closely related to the mustelids and to the pinnipeds, probably diverging from them just before the mustelids and pinnipeds diverged from each other. 45  This fact would mean that a relatively swift divergence among the three groups occurred, to explain why the reconciliation of DNA data with fossil data is problematic.  As Arnason and Widegren said,

"It is likely that the evolution of otariids and phocids (subdivisions of pinnipeds) was fast in the early stages of marine adaptation; hence evolutionary linkages with mustelids may be difficult to establish by means of paleontological findings." 46

It would not be the only rapid diversification to occur among the carnivores.  There was also a swift three-way split of the feline lineage into cats, vivets, and hyaenas. 47 

Swift divergence among pinniped ancestors was followed by a much longer period of about 23 million years during which natural selection made comparatively small adjustments, causing adaptive radiations at the genus and species level, which resulted in speciation within the pinniped group.  Moreover, the transformation is not complete, for the pinnipeds today fill an ecological niche similar to that of the ancestors to whales Pakicetus and Ambulocetus, which were partly terrestrial and partly aquatic.  Given several millions of years, the pinnipeds might evolve to become fully aquatic like the whales.  Yet this is still occurring in slow motion. 

The pinnipeds exemplify the operation of two distinct mechanisms – one mechanism being natural selection, which brought about gradual evolution with regard to the diversification among seals, sea lions, and walruses; and the other mechanism being some poorly understood mutational force which catalyzed an evolutionary event so rapid and so intense that it brought about a radically new and different form while leaving only a trace in the fossil record.

Turtles

The first turtle fossil, Proganochelys, dates to 220-205 million years ago.  Proganochelys looked much the same as turtles do today.  Among other traits it shares with modern turtles, it was nearly toothless, it had a fully developed shell both on top and on bottom, it was low to the ground, its head was roughly the same size as that of a modern turtle, and in all major respects it was a turtle.  However, it could not fully retract its head under its shell. 48

Nothing like turtles had ever existed before.  Gould et al described the sudden appearance of turtles as "A whole new reptile order appearing out of nowhere." 49 

Lee also acknowledged the lack of a missing link, stating, "Our understanding of chelonian (i.e. – turtle) origins has been restricted by a paucity of information on intermediate forms," yet Lee attempted to explain turtle origins by suggesting that the turtles are descended from the pareiasaurs, a group of large armored plant eating beasts. 50 

Turtles and pareiasaurs were very different.  If they were closely related, a theory which is debated, there are still a multitude of missing links between them.  Most obviously, Proganochelys had a shell of bony armor over its back, fused to its ribs, and another plate of armor under its belly.  The pareiasaurs had no such plates of armor.  They did have bony scutes floating under the skin, but these were not fused to the ribs, and were not connected to each other to make a plate.  Proganochelys had very small teeth, but the pareiasaurs had thick long teeth.  In the neck, Proganochelys had four spines per vertebra, two to each side, sticking outward.  Pareiasaurs had only one upper chevron located on the vertebra, not to the side.  Along the torso, the vertebrae of Proganochelys were elongated under the shell.  The pareiasaur vertebrae were not, and they had a different number of vertebrae in the torso than did the turtle.  Proganochelys had no chevrons on the vertebrae of its torso.  Pareiasaurs had such long upper chevrons that they actually stuck out of the skin, making a row of knobby spikes along their backbone.  Proganochelys had a club on its tail, pareiasaurs did not.  The upper chevronson Proganochelys' tail vertebrae were short.  The pareiasaurs' were long.  The length and number of vertebrae in the tail of Proganochelys was less than that of the pareiasaurs.  These are just a few of the differences between the two.  One thing they did have in common was their descent from the anapsids – reptiles without holes in their skulls.  As such, they are at least distant relatives.

The close ancestors of the turtles apparently evolved so rapidly that they did not leave any trace in the fossil record.  Yet Proganochelys does not show the markings of intelligent design by a perfect God, for Proganochelys was still an imperfect turtle.  Its tail was long, and it could not retract its head under its shell to escape predators.  Whatever catalyzed the rapid evolution of the turtles, it did so imperfectly.  Natural selection has since tweaked the structure of turtles toward improvement.

Lepospondyls

Certain early amphibians, the lepospondyls, also exhibit a pattern of rapid evolution.  They are all highly derived when they first appear in the fossil record, and as for their proposed ancestors, "there are no plausible intermediaries between them." 51 

Moss

From the plant kingdom, it has been observed that the Hypnales mosses underwent an "exceptionally rapid diversification" at the base of their history.  Yet their kinfolk, the Hookeriales mosses, may have enjoyed a steadier rate of diversification. 52  Thus, not all evolution is rapid evolution.  Some lineages, such as the Hookeriales, are characterized by slower, more gradual evolution, as is expected under the Darwinian model, while others are more rapid.

Ichthyosaurs

The ichthyosaurs were marine reptiles which lived slightly before and during the time of the dinosaurs.  They superficially resembled dolphins, but were actually quite different – having side-to-side tail propulsion rather than up-down tail propulsion, and having both front and hind fins rather than just front fins. 

The earliest fossils of the ichthyosaurs occur in the Olenekian period of the early Triassic.  Nine different genera of ichthyosaurs suddenly appear in the Olenekian, 53 thus indicating that a rapid evolutionary emergence of the ichthyosaurs was quickly followed by their subsequent speciation into a variety of diverse types – both the sudden emergence and the diversification being completed perhaps within 2 to 4 million years.  By comparison, the whales took about 20 million years to adapt completely to marine life, and another 15 million years to diversify into their current forms.  According to Calloway,

"Even the oldest known ichthyosaurs are completely adapted to marine life and have no close, gross morphological resemblances to any other reptiles… (this) has posed perplexing problems regarding the ancestry, early evolutionary history, and phylogeny of the group." 54

The ichthyosaurs subsequently inhabited the Mesozoic oceans for another 152 million years until apparently going extinct at the Cenomanian-Turonian boundary of the mid-Cretaceous. 55  During their long tenure, they diversified into a number of varieties.  Some of them evolved fish-like dorsal fins and tails. 56  Others evolved stereoscopic vision and specialized teeth. 57  Hundreds of species have been named and thousands of fossils of have been found. 58

There is a report of one primitive-looking ichthyosaur from the Spathian of Japan, which although appearing primitive in some ways, was already advanced enough to be obligatorily aquatic, as its flippers could not move its body around on land.   Motani et al suggested it is an intermediary between terrestrial reptiles and aquatic ichthyosaurs.  However, its age, 240 million years ago, is about 10 million years after the ichthyosaurs first appeared. 59  As such, it occurs too late to be a directly ancestral missing link, although, like the snakes with legs and the feathered dinosaurs discussed above, perhaps it is a descendent of a missing link.  The existence of an intermediary such as this, among early specimens of a lineage, indicates that the new form truly did evolve – it was not created.  If it were created by an all-wise God, then what is the purpose of the intermediary?  Was the intermediary poorly designed?  Did God fail in the first attempt? 

The most natural explanation for these data is neither creation nor gradual evolution.  Rather, it is that evolution acted rapidly to bring about a radically new and different form – so rapidly, in fact, that there was not enough time for missing links to accumulate in the fossil record. 

Sauropterygians

Sauropterygians were a highly diversified lineage of marine reptiles contemporary with the ichthyosaurs and later with the mosasaurs.  Early sauropterygians first appear at the Olenekian-Anisian boundary some 245 million years ago, about the same time as the ichthyosaurs' sudden origin.  At their first appearance, the sauropterygians were already diversified into several genera, including Cymatosaurus, Dactylosaurus, Proneusticosaurus, Nothosaurus, Placodus, Hemilopas, Saurosphargis, as well as indeterminate members of the family Pachypleurosauridae. 60  Both they and the ichthyosaurs are "very distinct from any putative ancestor when they first appear in the fossil record." 61 

They continued to gradually diverge into several families, genera, and species. 62  In one example, the divergence of the long-necked plesiosaurs and the short-necked pliosaurs is evidenced by intermediate teeth from the Lyme Regis formation, which suggest that a gradual divergence between the two forms occurred in the early Jurassic. 63  It also appears that primitive sauropterygians, unlike the ichthyosaurs, were not capable of trans-Pacific migration until sometime after the Carnian, at least 30 million years or more after their debut. 64  Some of the sauropterygians, such as the nothosaurs, make good intermediaries between land and sea creatures, for they possessed longer limbs with foot-like paddles.

A common myth of evolution is that every organism is "perfectly adapted to its environment."  The truth is, not every organism is so perfectly adapted.  In the case of the sauropterygians, a critical adaptive deficiency existed, which they never evolved to overcome, despite their long tenure of 180 million years on the planet.  They suffered from decompression syndrome, which is the deterioration of bones due to excess nitrogen in the blood caused by diving deep under water.  Unlike sauropterygians, whales have evolved cardiovascular adaptations to successfully avoid this problem. 65  Whales have accomplished this in less than 50 million years.  Yet the sauropterygians could not accomplish a similar adaption, even though they lived in the ocean more than three times longer than the whales.  It is a curious feature of evolution that these great beasts of the deep were able to develop all the necessary equipment for life in the water within a brief period, yet were unable to find a solution to decompression syndrome in 180 million years.  Apparently, there are limits to how far natural selection can take a form.

Bats

Bats popped out of the evolutionary woodwork about 55 million years ago.  They first appear as a radically new yet fully developed form, which was not in any way significantly different from modern bats.  Their debut in the fossil record is sudden, complete, and lacks intermediaries.  In 55 million years, they have changed little. 

Among the earliest bats is a 54.6 million year-old bat from Queensland Australia, which is similar to another early bat named Palaeochiropteryx. 66 Other early bat fossils include Icaronycteris 67and Onychonycteris. 68 

Modern bats are similar to these most primitive bats in all their most vital characteristics, including the same diamond-shaped skull, the same square rib cage followed by a sizeable and very distinct lumbar region, narrow bones in the limbs, the distance from shoulder to elbow is roughly two thirds the distance from elbow to wrist – and most obviously, the third, fourth, and fifth digits in the forelimb are long and narrow to support the wing.  It is this character, the length of the digits, which is most striking about the skeleton of bats, for it appears fully developed in the most primitive bats, with no link between it and the short fingers of its supposed insectivore ancestors.  The best explanation for this is that bats must have evolved very rapidly – so rapidly that intermediary forms did not last long enough to stand a good chance at being preserved. 

Yet Nature presented Onychonycteris as an intermediary, because it differed both from modern bats and from its contemporaries in having claws on all its fingers, rib and vertebral fusion, a shorter wingspan, and lack of echolocation ability.  However, there are some modern bats that do not echolocate, and some still have claws on more than one finger, so not all these characters necessarily make Onychonycteris a missing link.  Rather, they make it a different sort of bat.  In other respects Onychonycteris was similar to both modern bats and to its advanced contemporaries.  It had long narrow fingers, flapping flight, as well as a similar skull shape, pelvis, hind limbs, rib cage, scapula, clavicle, and sternum. 69 

Onychonycteris was a contemporary with the more advanced bats Icaronycteris and Palaeochiropteryx, and it is actually predated by the bat from Queensland Australia.  As with the small-limbed snakes and feathered raptors, it occurs too late in the fossil record to be a direct ancestor to the earliest bats.  Therefore, it cannot constitute evidence for a gradual transition from terrestrial insectivore to bat-like forms.  Nevertheless, its primitive characters, such as shorter wingspan and claws on all fingers, can plausibly be interpreted as intermediary features.  Hence, although this fossil indicates that a transition did indeed happen, it does not support that such a transition was necessarily gradual.  Rather, the fact that it was contemporary with advanced modern-like bats supports the theory that bat evolution happened rapidly.  That is to say, when the intermediaries do not predate the fully developed forms, then evolutionary transitions most likely took place over periods of time that were so brief that missing link fossils were not preserved.

If the distinctive characters of bats evolved by means of natural selection, such evolution must have occurred gradually, over a multitude of generations, as natura non facit saltum mandates.  If this were the case, then we should see a gradual change from insectivores to bats in the fossil record.  Instead, we find a sudden appearance of fully-formed advanced bats, without intermediaries before them.  Some would take this as evidence against evolutionary theory, and assert that God created the bats from scratch.  But this cannot be supported by the data, for the bats did not persist as immutable species each after its own kind.  Rather, the bat lineage has subsequently diversified into more than 200 genera. 70  This must mean that species have been morphing into other species.  This has happened gradually, as natural selection has caused bats to adapt to a multitude of different ecological niches, which are well represented in the fossil record. 

The evolution of bats follows the same pattern seen time and time again in the fossil record:  Sudden emergence of a new body plan followed by an adaptive radiation.  That is, evolutionary advancements involving gross morphological changes occur suddenly; however, what is gradual is the manner in which the species possessing those advancements adapt to fill every environmental niche permitted by the advancement. 

Recapitulation

Concerning existing forms, the following patterns permeate the history of life on earth:

1. Existing forms evolve gradually over time in accordance with the expectations of Darwin's theory of natural selection.
2. Some improvements to a form are surprisingly slow in evolving, or never do evolve.
3. Existing forms can adapt to a wide variety of environments.  They don't need to become new phyla to adapt.
4. The best conclusion is that evolution by means of natural selection happens slowly and is limited in the degree of change it can effect on a form.

      Concerning new forms, a different set of patterns permeate the history of life on earth:

1. New forms appear suddenly.
2. Intermediaries exist, but they come after the new form is already established, and therefore cannot be direct ancestors of the new form.
3. The best explanation for this is that new forms evolve so rapidly that missing links do not have enough time to leave an adequate fossil record; and that the intermediaries we see are descendents of missing links, not the missing links themselves.

Therefore, we have two types of evolution.  One is gradual.  The other is rapid.  One explains small changes.  The other explains big changes.  One is adequately explained by Darwin's theory of natural selection.  The other is more difficult to explain.

Mesonychid Skull, American Museum of Natural History

Acanthostega Replica, American Museum of Natural History

Allosaurus Skull, College of Eastern Utah

Platycarpus Mosasaur Skeleton, Denver Museum of Natural History

T-Rex Foot, Wyoming Dinosaur Center

Archaeopteryx

Compsognathus, New Mexico Museum of Natural History

Utahraptor, College of Eastern Utah

Pterosaur Skull, Wyoming Dinosaur Center

Pinniped, Smithsonian

Proganochelys, American Museum of Natural History

Parieasaur, American Museum of Natural History

Ichthyosaur, Utah Museum of Natural History

Icaronycteris compared to Modern Bat, American Museum of Natural History