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A restoration of the Cretaceous snake Sanajeh about to gulp down a baby sauropod. Model by Tyler Keillor, photographed by Ximena Erickson.

In 1925, when Yale University paleontologist George Wieland published a paper titled “Dinosaur Extinction,” no one knew why the great archosaurs had disappeared. The fact that the extinction of the dinosaurs was even worth explaining was a new idea. From the time dinosaurs were initially described in the early 19th century through the beginning of the 20th, their existence and disappearance simply seemed to be part of a grand progression of life that required no special attention or explanation. Even when paleontologists began to puzzle over why the dinosaurs vanished, many thought that dinosaurs were inevitably doomed by strange, internal growth factors that made them so large, stupid and ornate that they could not possibly adapt to a changing world.

But Wieland took a slightly different view. While his paper was more opinion than science—there was nothing measured, quantified or tested in the article—Wieland believed that he had perhaps identified some of the “invisible influences” that triggered the demise of the dinosaurs. Egg-eaters were of primary concern.

Wieland was not the first to suggest that the destruction of dinosaur eggs led to the group’s extinction. As pointed out by Wieland himself, paleontologists Charles Immanuel Forsyth Major and Edward Drinker Cope had previously speculated that small mammals may have raided dinosaur nests so frequently that Triceratops and its Mesozoic ilk were incapable of reproducing successfully. This hypothesis seemed plausible in general, but Wieland disagreed about mammals being the primary culprits. Small Mesozoic mammals seemed too weak to break open tough dinosaur eggs, and the most voracious modern-day nest thieves seemed to be those reptiles capable of swallowing eggs whole. “The potent feeders on dinosaur eggs and young must be sought for amongst the dinosaurians themselves,” Wieland remarked, “and perchance, amongst the earliest varanids [monitor lizards] and boids [boa snakes].”

Wieland believed that egg-eating must have been rampant during the age of the dinosaurs. In fact, he thought that a diet of eggs may have even led to the evolution of some of the largest of all predatory dinosaurs. Considering the giant Tyrannosaurus, Wieland wrote, “What more likely than the immediate ancestors of this dinosaur got their first impulse toward gigantism on a diet of sauropod eggs, and that, aside from the varanids, the theropod dinosaurs were the great egg-eaters of all time?” The cruel irony of this idea was that the immense predatory dinosaurs also reproduced by laying eggs, and Wieland considered it “quite inferable” that their nests, in turn, would have been raided by smaller monitor lizards and snakes.

Dinosaurs were not entirely defenseless against such attacks. Though dinosaurs were often thought in the 1920s to be reptiles write large, Wieland speculated that dinosaurs would have provided some parental care, were probably more active than living lizards and crocodiles and, among the egg-eating varieties, may have even sought out unprotected nests in coordinated “droves.” “With such active and powerful beasts at the jungle-edge,” Wieland wrote, “life was varied and sanguinary, be it within scientific dignity to say so.” Unfortunately, an active and varied existence could not save the dinosaurs. Both ecological factors and the supposed inability of dinosaurs to change sealed the fate of the dinosaurs, Wieland concluded; the great loss of eggs and the “racial senility” of dinosaurs ultimately ushered the group into extinction.

When Wieland wrote his paper, he could only speculate about predation on dinosaur eggs and babies. In the decades since, however, paleontologists have turned up rare fossil evidence that small predators truly did snap up young dinosaurs in various stages of development. In 2010, paleontologists announced the discovery of Sanajeh, a late-Cretaceous snake that may have fed on the eggs of sauropod dinosaurs. Several years before that, a different team of paleontologists found several baby Psittacosaurus skeletons in the fossilized stomach contents of the opossum-sized mammal Repenomamus, and in a 1994 paper, paleontologist James Kirkland suggested that small crocodyliforms like the slender Fruitachampsa may have also gobbled up eggs and little dinosaurs since their bones are sometimes found in association with dinosaur nests.

Despite these recent discoveries and hypotheses, however, there is no indication whatsoever that dinosaurs were driven to extinction by egg-eaters, reptilian or otherwise. Perhaps such a view was tenable when only a few dinosaur genera were known and we understood very little about their ecology, but not now. We have a greatly revised understanding of what happened at the end of the Cretaceous—a mass extinction that wiped out not only the dinosaurs, but a vast swath of life forms on land and sea. There is no hint of a run on dinosaur eggs in the fossil record, and the various types of supposed egg predators lived alongside dinosaurs for millions of years without killing off their egg-laying food supply. Dinosaur eggs certainly were a nutritious resource that were undoubtedly exploited by carnivores and omnivores, but such depredations were not the keys to dinosaur extinction.

References:

Wieland, G. 1925. Dinosaur Extinction. American Naturalist. 59 (665): 557-565

Triceratops was one of the last dinosaurs. What would the descendents of this ceratopsid look like if they were alive today? Photo taken at the Smithsonian National Museum of Natural History by the author.

In Slate’s recent poll for 2011′s “Question of the Year,” dinosaurs came in third. “Why are smart people usually ugly?” was the winner. Spoiler: the answer is, “they’re not.” But my favorite Mesozoic archosaurs were respectable runners-up with the question: “Let’s say that a meteor never hits the earth, and dinosaurs continue evolving over all the years human beings have grown into what we are today. What would they be like?”

There is an easy answer for this. Dinosaurs truly did survive the end-Cretaceous extinction and continued to evolve. Birds, the descendants of one lineage of feathered maniraptorans, carry on the dinosaurian legacy. But I imagine this isn’t what the reader who posed the question had in mind. Birds seem categorically different from the collection of impressive, non-avian dinosaurs that roamed the planet prior to 65.5 million years ago. Had Tyrannosaurus, Triceratops and their ilk been given an indefinite stay of execution, what would their descendants look like?

Pondering the form of future dinosaurs has been a long tradition in paleontology. Charles Lyell, one of the 19th century founders of modern geology, thought that the progression of life through time was so closely tied to certain climatic conditions, in turn created by geological changes to the continents, that one day habitats appropriate for prehistoric organisms might reappear. At some future time, Iguanodon, Megalosaurus and others might return to lush, primordial forests created by a replay of Mesozoic conditions.

Early 20th-century paleontologist William Diller Matthew suggested a different path by which dinosaurs might return. If mammals suddenly disappeared, today’s lizards, turtles and crocodiles might evolve into dinosaur-like creatures. Naturalist John Burroughs disagreed. “Does not the evolutionary impulse run its course? Can or will it repeat itself?” he asked, and he pointed out that evolution does not run according to pre-determined pathways. Even if reptiles someday rise to dominance, we would expect the descendants of modern forms to be distinct creatures substantially different than anything that has come before. It is not as if there is some vacant “dinosaur niche” in the evolutionary ether that reptiles will fill as soon as they get the chance.

Of course, paleontologists batted around these ideas before the full catastrophic magnitude of the end-Cretaceous mass extinction was discovered. The more we learn, the more mysterious the disappearance of the non-avian dinosaurs becomes—how could such a widespread, disparate and successful group be driven to extinction in a geologic instant? Dinosaurs showed no sign of slipping into evolutionary irrelevance or becoming outmoded, as was the traditional 20th century belief. They seemed to thrive right until the end.

The shift in our understanding of dinosaur extinction—as well as a refreshed image of dinosaurs as highly active, behaviorally complex, intelligent animals—generated at least two different thought experiments. In 1982, paleontologist Dale Russell collaborated with artist Ron Séguin to create the “Dinosauroid,” a speculative vision of what the small and relatively smart deinonychosaur Troodon might look like had the dinosaur survived the mass extinction and continued to evolve. The result was similar to the Sleestaks on The Land of the Lost, or the big-headed alien archetype that is ubiquitous in science fiction. Since Troodon was a relatively brainy dinosaur, and Russell believed that the human body was the optimal physical manifestation of a highly intelligent creature, he molded the dinosaur into humanoid form. But there’s no reason to think that our bodies represent the best possible conveyance for smart organisms. Crows, for one, are exceptionally smart, tool-using birds that demonstrate that dinosaur descendants evolved a high degree of intelligence in a body quite different from our own. If dinosauroids evolved at all, they would probably look like the raptor-like, feather-covered beings envisioned by artist Nemo Ramjet.

Dougal Dixon considered a similar idea in 1988 in his book The New Dinosaurs, although he entirely canceled the Cretaceous extinction and played with a wider variety of dinosaurs. Published before paleontologists confirmed that many coelurosaurs were covered in feathers, Dixon’s colorful creatures were often coated with fuzz or similar hair-like coatings, and many were cast as counterparts to modern day mammals. The small “Waspeater” was the dinosaur answer to the tamandua, a tree-dwelling anteater, and the tiny “Gestalt” was effectively one of the dome-headed pachycephalosaurs refashioned to be a naked mole rat. A few of Dixon’s dinosaurs maintained the monstrous forms that we adore, though. Dixon’s “Lumber” was effectively a Diplodocus with a short, fleshy trunk—an idea that was actually kicked around and ultimately discarded by paleontologists—and the “Gourmand” was a tyrannosaur that had entirely lost its forelimbs and took the appearance of a giant, two-legged crocodile.

Many of Dixon’s speculative animals suffered from the same problem as Russell’s dinosauroid—they were dinosaurs molded to fit the natural history of creatures we see around us today. It is impossible to say whether such creatures might have ever existed had history took a different course. As Stephen Jay Gould pointed out in Wonderful Life, we cannot go back to some critical moment in evolutionary history and “replay life’s tape” to see how nature might be altered. We can be certain of one thing, though—modern dinosaurs would be significantly different than anything we know from the fossil record.

As John Burroughs rightly pointed out in his argument with William Diller Matthew, evolution does not proceed along a pre-set course. The major patterns of evolution are not predictable. Contrary to once-popular, non-Darwinian evolutionary mechanisms, there are no internal driving forces that cause evolution to repeat itself or force organisms along ladders of progress toward some ideal type or form. Nor is natural selection so demanding that all lineages are constantly being fashioned into a small handful of forms.

The fossil record clearly shows that the big picture of evolution is a fantastically branching bush of diversity and disparity in which chance, contingency and constraint all have significant roles to play. Some lineages will rapidly and drastically change, and others will remain in relative stasis over millions and millions of years. Perhaps some dinosaur lineages, like sauropods, would remain more or less the same, while horned dinosaurs might undergo dramatic changes into something different. After all, 65 million years is about the amount of time that separated Late Triassic dinosaurs like Coelophysis—a small theropod which lived alongside various other wonderful archosaurs before the onset of dinosaur dominance—from Allosaurus, Stegosaurus, Apatosaurus and other titans of the Jurassic. Sixty-five million years is plenty of time for spectacular changes to transpire.

How lineages might change is squarely within the realm of speculation. But we can expect that new dinosaur species would continue to evolve, just as they had been since the Late Triassic. Dinosaur species did not last very long—even the longest-lived species were around for only about two million years or so—and if we are working from the premise that dinosaurs would have survived to the present, we would expect to see an entirely different cast of dinosaur species. Some might look familiar, and others might be entirely alien to us, but all the surviving dinosaurs would be different from their Cretaceous ancestors.

This is why I’ll be watching Pixar’s upcoming dinosaur film with interest. The film fleshes out the premise that I’ve been prattling on about, although, in the animated fantasy, the dinosaurs live alongside humans. (That’s fine for the movies, but, had non-avian dinosaurs actually survived, mammal evolutionary history would have been severely altered. If the end-Cretaceous extinction was canceled, our species would not have evolved to debate the question of what would have happened in alternate timelines.) I hope that Pixar fashions a new dinosaur cast. Tyrannosaurus, Barosaurus, Centrosaurus and Edmontosaurus do not belong in the alternate present. They would have disappeared long ago, ultimately replaced by different genera and species. Even if we can’t know how non-avian dinosaurs changed during the past 65 million years, we should at least recognize that the survivors would have undoubtedly evolved into new species, and new species would have branched off from those, and so on and so on until the present day.

So, to answer Slate’s question, we don’t know what dinosaurs would be like. All we know for sure is that at least one variety of dinosaurs is still here, and that’s a wonderful thing.

Tyrannosaurus faces off against Triceratops at the Natural History Museum of Los Angeles. Some early 20th century paleontologists thought the size and weapons of these creatures indicated that dinosaurs were degenerates due for extinction. Photo by the author.

I hate the phrase “going the way of the dinosaur.” I cringe almost every time I see it. Political and business journalists are the worst offenders. When a politician begins to lose favor or a company is outmoded, such writers often draw a parallel between their subjects and the classic image of dinosaurs as stupid, swamp-dwelling brutes who ultimately lose life’s race to the quicker, smarter mammals. This metaphor has been around for a century, at least, and has its roots in a time when dinosaurs were thought to be creatures that became so big and fierce that they could no longer survive.

As music composer Deems Taylor explained before the prehistoric segment of 1940′s Fantasia, dinosaurs were once seen as “little crawling horrors,” “100 ton nightmares”, “bullies” and “gangsters.” Dinosaurs had come to rule the world through strength alone and evolution ultimately left them behind as imperfect monsters. The mystery wasn’t why dinosaurs died off, paleontologists believed, but how they had managed to dominate the planet for so long.

Some paleontologists believed that dinosaurs simply walked off the evolutionary stage when their time had run out. This was an extension of a weird idea known as “racial senescence”–a discarded idea that flourished during a time when paleontologists disagreed about the causes of evolution and extinction.

Even though Charles Darwin had beautifully articulated the idea of evolution by means of natural selection in 1859, and many naturalists subsequently agreed that evolution was a real phenomenon, natural selection was  frequently criticized. Some scientists were disgusted by the violence that seemed inherent in natural selection–the emphasis on competition for survival–and, alternatively, others argued that a gradual, stepwise process was not powerful enough to affect major change. As historian Peter Bowler has documented in books such as The Eclipse of Darwinism and The Non-Darwinian Revolution, late 19th and early 20th century naturalists often turned to alternative evolutionary mechanisms to explain fluctuations in form through time –bizarre, difficult-to-define forces that somehow dwelt inside organisms and drove the creation of new forms.

Racial senescence was one of these ideas. Paleontologist Richard Swann Lull explained the concept in his 1917 textbook Organic Evolution. Just as an individual creature was born, grew up, declined in health and expired, species also went through a similar pattern of birth, growth and decline. In fact, naturalists believed that there were tell-tale signs that a lineage was at death’s door. Following an outline by colleague Arthur Smith Woodward, Lull identified signs of “racial senescence” as a relative increase in size, a tendency for organisms to grow spectacular spikes and spines (old lineages no longer had the ability to control the wild growth of their skeletons, in his view) and a general pattern of “degeneracy”, such as the loss of teeth and other prominent characteristics.

Lull cited dinosaurs as examples of some of these trends. The immense Jurassic sauropods “Brontosaurus” and Brachiosaurus seemed perfect examples of increased size preceding extinction, as both were then believed to be among the last of their kind. (The wealth of fantastic Cretaceous sauropods we now know had not yet been uncovered.) Likewise, Tyrannosaurus–among the largest terrestrial carnivores of all time–lived at the terminal point of dinosaur history.

Stegosaurus was an even better example of senescence. Not only was the dinosaur large and apparently the last of its kind–at least as far as paleontologists knew circa 1917–but the dinosaur also displayed a “marvelous overgrowth of armor plates and tail spines which heightens the bizarrerie of this most grotesque of beasts.” Naturalist Charles Emerson Beecher tried to explain the mechanism by which this would lead to extinction in his book The Origin and Significance of Spines. Beecher considered spines and other ornaments to be outgrowth of “dead tissue,” and as a species accumulated such adornments there was less available space and energy for “living tissue.” Dinosaurs such as Stegosaurus and Triceratops, therefore, might have painted themselves into an evolutionary corner by developing wonderful armaments.

Regarding teeth, Lull explained that dinosaurs such as the sauropod Diplodocus and the ostrich-like Struthiomimus were suffering a reduction in the number of teeth–what the paleontologist thought was an almost sure sign the animals had reached evolutionary old age. Other naturalists concurred. Horatio Hackett Newman borrowed some of the same examples for his 1920 textbook Vertebrate Zoölogy, and considered dinosaurs such as the sauropods to be unfortunate geriatrics. Contrasted with species in their prime, Newman wrote than an old lineage “is characterized by sluggish behavior, by herbivorous habits or feeding habits involving little exertion, by structures on the whole specialized or degenerate, often by giant size or bulky build, and by accumulations of inert materials such as armor, spines, heavy bones or flesh.”

Yet the distribution of supposedly degenerate dinosaurs perplexed Lull. Some forms he identified as “senescent”–such as the stegosaurs and sauropods–supposedly slipped into extinction long before the final disappearance of dinosaurs as a group. Turtles and birds also underscored this problematic wrinkle–Lull considered that both turtles and birds were degenerate because they lacked teeth, yet turtles had been around longer than the dinosaurs and birds showed no sign of dying out. Nevertheless, Lull was confident that the dinosaurs had “died a natural death.” Their time had simply run out, although the puzzle was why such apparently unhealthy and degenerate creatures were able to survive for so long. Only mammals–creatures thought to be more evolutionary “advanced” than the dinosaurs–were thought to suffer rapid, catastrophic extinctions due to forces such as changing climate.

Dinosaurs seemingly couldn’t help themselves. They just got bigger and stranger until they simply could not change anymore. The “way of the dinosaur” was one of weird extravagance ultimately culminating in an extinction pre-ordained by evolutionary paths. Yet, even when such ideas were in fashion, contradictory evidence had to be overlooked.

According to the outline of racial senescence, dinosaurs should not have survived past the Late Jurassic, yet they thrived for millions and millions of years after the time of Apatosaurus and Stegosaurus. Additional fossil finds have also documented that many of the so-called degenerate lineages did not actually go extinct when Lull, Newman and their peers thought, and the recognition that natural selection is the primary driving force behind evolutionary change disintegrated muddled ideas about internal life forces and evolutionary life clocks. Dinosaurs did not die out because evolution programmed them to self-destruct. The Dinosauria was one of the most successful vertebrate lineages in all of history, and the ultimate extinction of the non-avian forms around 65.5 million years ago was simply an unlucky turn. At this point in time, paleontologists have turned Lull’s question on its head–we are getting a better idea of why dinosaurs dominated the planet for so long, and their ultimate disappearance has become ever-more perplexing.

A cast of the sauropod Diplodocus at the Utah Field House of Natural History in Vernal, Utah. Our current understanding of sauropods like this differs greatly from hypothetical restorations of "living dinosaurs" in Africa. Photo by the author.

In the annals of science fiction, humans and non-avian dinosaurs have been brought together in a variety of ways. Genetic engineering experiments and time travel are probably the most common these days, but I have always had a soft spot for tales of “lost worlds.” What could be more fantastic than dinosaurs that somehow escaped extinction and persisted in some isolated spot for 65 million years? My childhood self really wanted someone to find a living Tyrannosaurus, Apatosaurus, or Triceratops in some remote locale, and that wish was fed by reports that one elusive dinosaur was hiding in Africa.

First thing first—living dinosaurs certainly do exist. We know them as birds, and a combination of fossil discoveries and laboratory research has confirmed the evolutionary connection between birds and feather-covered maniraptoran dinosaurs. But from time to time, people have proposed that non-avian dinosaurs may also still be hanging around.

The most famous of the supposed living dinosaurs I heard about was Mokele-mbembe. This unknown creature—often restored as a swamp-dwelling, tail-dragging sauropod akin to old restorations of “Brontosaurus“—is said to inhabit the dense jungle in what is now Cameroon and the Democratic Republic of the Congo. At least, that’s the way I was introduced to the legendary animal in the late 1980s. A blurry photograph of a lump in a lake and an ambiguous sound recording made by Herman Regusters during a 1981 expedition to find the animal were cited as possible evidence that a semi-aquatic sauropod was swimming around Lake Tele, and the feature film Baby: Secret of the Lost Legend fleshed out the hypothetical dinosaurs. Tall tales and legends of Mokele-mbembe had been circulating for decades before, and sensationalist basic cable television programs still fund expeditions to try and find the animal from time to time.

Is there any good evidence that a sauropod still wades through the muck of African swamps? Sadly, no. I would be thrilled if a living, non-avian dinosaur really did turn up somewhere, but such a fantastic find would have to be backed up by equally fantastic evidence. Despite the fact that multiple expeditions have been sent to the Democratic Republic of the Congo over many years, there is no solid evidence that Mokele-mbembe is a dinosaur or even a real, unknown species of animal. I seriously doubt anyone will ever find any evidence of such a creature at all, and part of the reason why related to a paper published by University of Queensland zoologists Diana Fisher and Simon Blomberg last year.

The major message of Fisher and Blomberg’s study was positive: Some modern mammal species thought to be extinct may still survive in small, hard-to-find pockets of their former ranges. But the researchers also noted that the effort put into finding supposedly extinct species makes a difference as to whether we should expect to find those animals. The researchers found that species that still survived were often found after three to six searches, but if more than eleven searches were made with no results—as is the case for the Tasmanian tiger and Yangtze river dolphin—then the species is probably actually extinct. Since so many searches have been made for Mokele-mbembe with no solid results, I don’t think that there’s actually any large, hidden species there to find.

There is a flipside to that argument, although it also doesn’t bode well for the rumored dinosaur. Many of the searches for Mokele-mbembe have been made by self-described explorers who have little to no relevant field experience in tracking and studying wildlife. Some of these folks are even religious fundamentalists who are striving to somehow undermine evolutionary theory. Their credibility is highly suspect, but you would think that at least one group would have blundered into the animal by now. After all, there has to be a population of animals which would be leaving tracks, scat and occasionally bodies. The evidence for huge creatures living in the swamp should be readily apparent, and the best the many dinosaur hunters can come up with are tall tales and misshapen globs of plaster that look nothing like the tracks the casts are claimed to be.

But the most obvious problem is that there’s no trace of sauropods in the fossil record—at all—in the 65 million years since the end-Cretaceous extinction. Nothing. The last of these dinosaurs died out long ago, and there is not even a scintilla of evidence that sauropods survived past the close of the Mesozoic. If sauropods survived at all we would expect to find some indication of their existence in the fossil record. These were not small animals or creatures that were hidden away in the deep sea. Given the number of terrestrial fossil deposits and they way they have been sampled, Cenozoic sauropods would have turned up by now if they had survived.

There are plenty of other problems with the idea that there’s a sauropod trundling around in the swamps of the Congo Basin. One of the most ridiculous aspects of Mokele-mbembe stories is that the supposed dinosaurs resemble what the searchers expected sauropod dinosaurs to look and act like based on inaccurate restorations. The hypothetical dinosaurs act just like their counterparts in old Charles R. Knight and Zdeněk Burian paintings. Actual, living sauropods would have looked markedly different from those old restorations, and according to recent research, sauropods would have been really lousy swimmers due to the considerable volume of air-filled spaces in their bodies. A sauropod would not be able to act like a crocodile and hide underwater as Mokele-mbembe supposedly does. The weakness of the “Mokele-mbembe as sauropod” hypothesis is underscored by the fact that the supposed anatomy and behavior of the animal is clearly based on outdated images of dinosaurs. As Darren Naish pointed out in his brilliant April Fool’s Day post on Mokele-mbembe from this year, the idea that the animal was an old-school, tail dragging sauropod grates against everything we have learned about sauropods during the past three decades.

Paleontologist Don Prothero also took a few good whacks of Mokele-mbembe in a recent Monster Talk episode. Not surprisingly, Prothero points out that many of the reports about the animal are extremely inconsistent. A number of supposed sightings don’t refer to anything dinosaur-like at all, and even those that do are inconsistent and ambiguous. On top of that, Prothero and the show’s hosts bring up the fact that fanatics in search of Mokele-mbembe can easily misconstrue what local people might be saying about the animal because of a lack of shared cultural background and other translation problems. While visiting explorers often use the term “Mokele-mbembe” to refer to a supposed dinosaur or similar animal, the word can also refer to something that is not real or has no physical manifestation. If film crews and self-described explorers keep passing through and spending money in the region, it’s not surprising that people will tell the monster hunters what they want to hear.

The take-home lesson is this: If you want to find sauropods, sign up to volunteer on a professional fossil excavation with well-trained scientists.

Artist Donald E. Davis' depiction of the asteroid impact which played a critical role in the end-Cretaceous extinction. Image from Wikimedia Commons.

What if the non-avian dinosaurs didn’t go extinct 65 million years ago? Dinosaur fans love to ask the question—what if one of the most devastating extinctions of all time was cancelled?—and the speculative answers have ranged from fanciful to silly examples of our own arrogance. According to news released this week, the movie studio Pixar is getting ready to present its own version of what our world might look life had Tyrannosaurus, Triceratops and their kind been given a stay of execution.

In addition to future releases such as Monsters University and Wreck-It Ralph, WIRED reports that Pixar has announced it’s working on a movie given the thrilling temporary name “The Untitled Pixar Movie About Dinosaurs.” (This announcement makes sense of rumors that have been floating around since last year that Pixar has been working on a dinosaur project.) The general idea is, “What if the cataclysmic asteroid that forever changed life on Earth actually missed the planet completely and giant dinosaurs never went extinct?” CNN reports that “This hilarious, heartfelt and original tale is directed by Bob Peterson (co-director/writer, Up; writer, Finding Nemo) and produced by John Walker (The Incredibles, The Iron Giant).” Pixar’s dinosaur film is set to debut in late 2013.

When I heard the news, the first question on my mind was, “What sort of dinosaurs are we going to see?” Are we going to get classic Mesozoic dinosaurs, or are we going to get novel dinosaur species that are the descendants of the Cretaceous survivors? The movie could provide Pixar with a good opportunity to take a subtle but powerful stand for evolution—of course we shouldn’t see Stegosaurus, Brachiosaurus, Spinosaurus and other favorites because evolution would have kept on changing life during the past 65 million years! Actually, I would be a bit disappointed if Pixar didn’t try to introduce new dinosaurs. I know I’ve been critical of speculative dinosaurs before, but in this case, the premise demands species that have never been seen before. Life changes, and dinosaurs would have certainly continued to evolve.

(All this is ignoring the fact that dinosaurs are still around. We really do know what dinosaurs would look like if they survived, because birds—the modern descendants of dinosaurs—are everywhere. Since birds aren’t quite as thrilling as big honkin’ theropods and sauropods, though, it’s understandable that Pixar is focusing on the non-avian dinosaurs.)

Despite the poorly-executed cash grab that was this summer’s Cars 2, I still have faith in Pixar. Not only have they created some of the best animated films ever, they have been behind some of the best films to be released in the past few years, period. I can’t wait to hear more about their alternative history where dinosaurs still rule the earth.