April 20, 2002 | David F. Coppedge

Ichthyosaurs Suddenly Appeared in Triassic Oceans

“Ichthyosaurs were a group of Mesozoic marine reptiles that evolved fish-shaped body outlines,” begins Ryosuke Motani (UC Davis) in the Annual Review of Earth and Planetary Sciences,1 in a paper on “Evolution of Fish-Shaped Reptiles… in Their Physical Environments and Constraints.”  But while much is said about their environments and constraints, little is said to explain their evolution.  It is not even certain they were reptiles: “The sister group of ichthyosaurs is unknown,” he says, resulting in taxonomists proposing conflicting ideas of where to put them within the vertebrates: “Many different hypotheses have been proposed as to where ichthyosaurs belong in the tree of vertebrates, and all major groups, including mammals, amphibians, and osteichthyes [bony fishes], have been proposed.”  The majority view is that they are reptiles that diverged before the dinosaurs, though “It is unknown whether they are outside or inside the saurian clade.”  The classification problems continue inside the clade.  Even though “there seems to be a consensus regarding the basic phylogenetic relationship among major groups” of ichthyosaurs, “None of the published phylogenetic trees is uncontroversial,” he notes.
    Ichthyosaurs are characterized by narrow snouts, usually conical teeth, and a bend in the vertebra near the tail.  They apparently ate fish and squid.  Some of them had enormous eyes, much bigger relative to body size than any other animal.  The number of fin digits varied from one to twenty.   “Ichthyosaurs were a diverse group, with various body forms and sizes,” writes Motani, an expert on this unusual group of swimmers.
    The first ichthyosaur was described in 1814, long before Darwin’s theory.  “Despite such a long history of scientific study,” Motani says, “our knowledge of the evolution of the group was limited until recently because interest in the group flagged, especially after the recognition of the Dinosauria (Owen 1842).  It was not until the late 1980s that the ichthyosaurian study was revitalized, and many of the noteworthy facts listed above were recognized during the past decade.”  Summarizing the latest discoveries and discussing future perspectives are the purposes of Motani’s review.
    “The first definitive records of ichthyosaurs appear suddenly and almost simultaneously over a wide range of the Northern Hemisphere, including Canada, China, Japan, and Spitsbergen,” in the upper Triassic, he says, making it “difficult to discuss the geographic origin of the group.”  The earliest forms look like a “long-snouted lizard with flippers and a small caudal fin…, with a relatively small skull, an elongated trunk containing approximately 40 vertebrae in front of the pelvic girdle, and a short tail” (emphasis added in all quotes).  These were 1-3 meters in length.  Two other groups appear in Middle Triassic strata, one large (9m) and one small (2m), that disappear in the Late Triassic.  A group of tuna-shaped ichthyosaurs called Parvipelvia shows up in Late Triassic strata and became the dominant type in those rocks.  Ichthyosaur fossils appear throughout the Jurassic into the Cretaceous, when they all went extinct.  More fossils of new species are being found all the time.  Some finely-preserved, articulated specimens found recently in China are proving very interesting.  Yet putting all the diversity of ichthyosaurs into an evolutionary timeline is made difficult by gaps:

The evolution of the intermediate grade ichthyosaurs during the Middle and Later Triassic is poorly understood at this point, and the diversity of ichthyosaurs in the Early Cretaceous requires further investigation.  Middle and Late Jurassic are also important, given the scarcity of materials known at his point.

Motani speaks often of evolution in his review, yet points more to species diversity than to any particular trends in morphology.  For instance, discussing the flippers, he claims “it is possible to trace the continuous evolutionary transformation series for the forelimb,” but then says, “Although the series is continuous, it is difficult to single out a feature that is shared by all ichthyosaurian front flippers.”  His elaboration presents a somewhat confusing picture:

Ichthyosaurs initially had five digits as in many amniotes, including humans.  Some time in the Late Triassic, a form without the first digit, or the thumb, appeared…, and this lineage eventually gave rise to the Parvipelvia.  Extra digits started to appear in some species of Norian ichthyosaurs, and many Jurassic ichthyosaurs added digits both anteriorly and posteriorly in the forelimb (Figure 4), a phenomenon referred to as hyperdactyly.  Ichthyosaurs also added extra finger bones, or phalanges, to their digits.  Such hyperphalangy was present even in the most basal ichthyosaurs, such as Utatsusaurus ….

So the earliest forms already had multiple phalanges and digits; some later forms had more, some had fewer.  Neither is there an evolutionary pattern in size: “There was no simple trend in ichthyosaurian body sizes through geological time,” he writes.  “Large as well as small ichthyosaurian species seem to have coexisted from the beginning.”  Most were under 10m, but a giant species possibly 20m was found near British Columbia.
    Motani says that ichthyosaurs were the “first tetrapod to evolve a fish-shaped body profile with a well-demarcated caudal fluke, long before cetaceans came up with a similar design some 150 million years later,” but merely assumes that three very different groups – reptiles, mammals and fish – all converged on the multiple structural and physiological features necessary for streamlined swimming.  He claims ichthyosaurs “evolved the largest eyes of all vertebrates” without saying how; later, he mentions, “It is not known why such an extensive bony coverage of the eyeball evolved.”
    Motani also discusses that ichthyosaurs “have one of the earliest records of live-birth in amniotes” without mentioning the transitions necessary to make it possible; in fact, this capability seems to have appeared abruptly in this group: “Given that ichthyosaurs did not appear until very late in the Early Triassic, live-birth clearly evolved early in the ichthyosaurian evolution, at least during the first few million years or possibly less, of their 150-million-year evolutionary history” — i.e., this complex adaptation suddenly appeared in the first 1% of their timeline and persisted unchanged throughout 150 million years, while other major changes in body shape evolved, including significant reductions in the pelvis.
    Motani’s only specific reference to a transitional form is “Californosaurus, which is one of the transitional forms between the fish-shaped and more basal ichthyosaurs, it is clearly seen that the change of the orientation of the neural spines corresponds to the position of the tailbend.”  Yet that change seems to represent only a rather minor difference in shape.  In another place, he admits that “The exact phylogenetic position for the appearance of the fish-shaped design in ichthyosaurs is controversial.”  The only other reference to transitional forms is: “The evolution of the group during the Early Jurassic can be considered as continued experimentation along the fish-shaped parvipelvian design that appeared in the Norian,” yet he does not elaborate on which descended from which, or which could be considered more fit or better adapted.
    However confusing the interpretation of ichthyosaurs remains, this diverse group of marine animals became an early icon of evolution: ichthyosaurs “were the first major fossil collected by Mary Anning in the 1800s (McGowan 1991), and, together with the plesiosaurs that she discovered later, they symbolize the early phase of scientific movements in England that cultivated the grounds for Darwin’s evolutionary theory.”
    Some of the most remarkable ichthyosaur fossils show the young in the process of being born.  At least six genera show embryos inside adult individuals. 


1Ryosuke Motani, “Evolution of Fish-Shaped Reptiles (Reptilia: Ichthyopterygia) in Their Physical Environments and Constraints,” Annual Review of Earth and Planetary Sciences, Vol. 33: 395-420 (Volume publication date January 2005) (doi:10.1146/annurev.earth.33.092203.122707)

Ichthyosaurs were a remarkable group of swimming animals.  Motani knows a lot about them, but he doesn’t know much about their evolution.  Despite his bluffing assertions about phylogeny, there is not a single point he makes that is without controversy or problems.  Even accepting the evolution-biased geological dates, he has to admit that the “basal” (earliest, presumably most primitive) ichthyosaurs already had five digits in functional flippers and gave birth to live young.  No subsequent evolution could be anywhere near as dramatic as having a full-fledged ichthyosaur appear in the fossil record without ancestors.
    They are not clearly related to any other group of vertebrates, yet in many respects are like reptiles in fish costumes.  The similarities in body shape between some ichthyosaurs and tunas or dolphins is uncanny.  Streamlined body design requires not just a skeleton, but the musculature and skin to deal with fast swimming.  Every other body system – digestive, circulatory, endocrine, nervous, sensory, excretory, reproductive, and immune – must also adjust when there are changes in morphology.  How many lucky mutations had to converge in just one species of ichthyosaur to get this all right, let alone in a tuna (bony fish) or dolphin (mammal)?  Since the last common ancestor of these three groups could not have possessed that genetic information, the Darwinist is forced to believe that these three distant groups illustrate an amazing example of convergent evolution, whatever that means.  But even accepting that cop-out explanation, Motani admits that the phylogenetic position of the fish-shaped ichthyosaurs is controversial.  They seem to appear fully streamlined out of nowhere.
    Consider also how remarkable it is to have numerous examples of fossils containing live embryos.  Marine creatures do not normally fossilize while carrying young.  A marine animal is either eaten or else dies of old age, not while giving birth.  For the embryos to be preserved, some even possibly in the process of exiting the birth canal, there had to be a sudden catastrophe that captured and smothered these large, strong creatures in mud before they could even appear startled.
    There is nothing in this story to suggest these creatures evolved from something else.  Diversity is not evolution.  Motani did not demonstrate any clear sequence of characters morphing into others, or new functional capabilities arising de novo; nor did he explain how mutations and natural selection could produce an interrelated suite of complex structures like an ichthyosaur.  He did not show how they originated in one location and spread around the globe.  On the contrary, they burst on the scene all over the world, from Canada to Europe to China, in a geological blink of an eye, without precursors.  The only thing of any certainty about evolution in this paper was his determination to force-fit every piece of data into a Darwinian belief system.  (Notice how these fossils were used as props for Darwin’s theory, even though 146 years later, scientists are still struggling to understand their evolution.)  There is much in this story, however, that fits the framework of creation and a worldwide flood.  Along with most other living things, these marvelously designed animals were carrying out their everyday life and bearing their young, when the flood came and destroyed them all.

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