Thursday, 28 May 2020

What really are the Jurassic Park Raptors supposed to be?

Fig 1: Many people may be surprised to know that the genus Velociraptor has been known since 1924. It however never gained much popularity until 1993’s release of the movie Jurassic Park. As such, appearances of it in art, books or let alone movies before the 90s are quite rare. Here we see one of those rare pre-90s depictions of the animal, made in 1975 by none other than Zdeněk Burian. The lizard in the foreground is Macrocephalosaurus, now classified as Gilmoreteius. Take that as foreshadowing.
Being born in 1998, most of the shows and documentaries I grew up with as a child (such as Dinosaur Planet and When Dinosaurs Roamed America on Discovery Channel) already portrayed dromaeosaurs as small, feathered and very bird-like animals and this is naturally how I now prefer them being portrayed. Despite already knowing at about age 6 that these movies were outdated, I am nonetheless a big fan of the Jurassic Park franchise, especially the original trilogy (yes, even the third one) and its surrounding media, as they allow me to imagine what the 90s Dinomania must have been like. Naturally, I also love to speculate about the in-universe lore of the series. One of the most fascinating topics of discussion are the stars or “main villains” of the movies, the Velociraptors. At this point it is probably common knowledge that, unlike the movie-version, the real-life Velociraptor mongoliensis was a turkey-sized, fully feathered animal (and yes, we do know for a fact that it had feathers thanks to phylogenetic bracketing and obvious quill-knobs along its arms) that would have resembled a hawk with teeth more than a bipedal monitor lizard. Even the newest Animal Crossing game has made fun of this fact, just ask Blathers! This obvious discrepancy, especially the one in size, has led a lot of people to question if the JP raptors are really meant to be Velociraptor or are actually an entirely different genus of dromaeosaur, with suggestions like Deinonychus, Utahraptor, Achillobator and Dakotaraptor often being thrown around. This post here was in part inspired by a recent blogpost by Mark Witton where he commented that he thinks at this point the JP raptors are not meant to represent any specific species, but just a generalized image of an eudromaeosaur. Many other speculations abound and I am sure many people reading this already have heard of or made up their own theories on the matter. This is basically just my personal take based on the available evidence, though I also want to clear up some common misconceptions I have heard from time to time.

Before we start I just want to clarify that I will refer to dromaeosaurs as “raptors” here purely for convenience sake. Personally I am still of the opinion that the term should be reserved for birds of prey specifically in other discussions to avoid confusion.

The case for the novel

Before there were any movies, there was just a novel by Michael Crichton, released in 1990 and taking place in 1989. While there are some important differences, the novel and the movie roughly follow the same plot and one of the main threats is a dromaeosaur classified in-universe as Velociraptor. Nowadays it is however general consensus that the raptors featured in the novel are actually Deinonychus, but there exist two different claims as to why its name was changed. Either A) Crichton just found the name Velociraptor cooler and allowed himself some artistic license or B) Crichton was following a controversial classification scheme at the time. As I think we will see, both versions of the story are essentially correct without contradicting each other.
Fig. 2: Deinonychus, a wolf-sized dromaeosaur from North America, as originally reconstructed by Robert Bakker for John Ostrom in 1969. The image, as well as the dinosaur, kickstarted the Dinosaur Renaissance and became the prototype of what the general public thinks a “raptor” looks like. Apart from it obviously lacking feathers, much of our anatomical knowledge about this dinosaur has changed too, especially the head-shape and hand-posture. 

Since its first description in 1969 up to 1993, Deinonychus antirrhopus was THE dromaeosaur known to the general public and in the focus of paleontologists, as it was the largest of its kind known up to that point, kickstarted the Dinosaur Renaissance and revived the hypothesis that birds descend from dinosaurs. Its smaller cousin Velociraptor, despite being known since 1924, was never popular and barely featured in books until the release of the first Jurassic Park movie. The most important researcher of Deinonychus at the time was of course its discoverer, John Ostrom. As Ostrom once recounted in an interview, after Crichton finished writing The Andromeda Strain, the author actually contacted the paleontologist to specifically ask him about details concerning Deinonychus, such as its range of motion and behaviour. Crichton was doing some research for his next novel. Ostrom further recounts that after Jurassic Park released, Crichton admitted to him that he based the novel’s raptors in pretty much every detail on Deinonychus, but chose the name of its relative Velociraptor as he thought it would sound more dramatic to an audience which probably did not understand Greek.
Fig. 3: As attested in the novel’s acknowledgements, Greg Paul’s book here was a great influence on Michael Crichton while writing Jurassic Park. The dinosaur on the cover is Yangchuanosaurus shangyouensis, known from nearly complete remains from the Middle Jurassic of China, but Paul classified it as a species of the genus Metriacanthosaurus (Paul 1988, p. 290-292), otherwise known from only a few bones found in England. Likely as a reference to this book, we can see in the movie, when Dennis Nedry is stealing dinosaur embryos, a testtube with the name Metriacanthosaurus on it, implying that the animal was being cloned for the park. Lately Metriacanthosaurus even appeared in the videogame Jurassic World Evolution, once again stealing the fame from the much better known Yangchuanosaurus. I am starting to see a pattern here.
Another main inspiration for Crichton (and the movies) was however also the book Predatory Dinosaurs of the World, written by Gregory S. Paul and released in 1988 (just one year before the events of the novel are supposed to take place). The book was one of the most thorough and comprehensive guides to theropod dinosaurs at the time and included many, now iconic, illustrations by Paul. However, it also lives on in a bit of infamy, as Paul expressed some quite controversial opinions in it. The thing he is still a bit infamous for today are his classification schemes. Paul is what taxonomists would call a “lumper” as he is fond of lumping/synonymizing taxa together under the same genus. There is nothing necessarily wrong about that if there are good reasons to do so, and some of Paul’s reclassifications have nowadays become consensus, such as Syntarsus/Megapnosaurus actually being a species of Coelophysis. However, many of his other classifications, such as both Styracosaurus and Pachyrhinosaurus actually being species of Centrosaurus, are either highly controversial or outright rejected today. The suggestions that Jack Horner gets hated on nowadays are a joke compared to the stuff Paul has sometimes proposed. It should be mentioned for fairness that Paul defended most of his ideas by using the standards some taxonomists use on modern living animals, such as the fact that lions, tigers, jaguars and leopards are all classified under the genus Panthera or that nearly all monitor lizards, from the nile monitor to the Komodo dragon and even Megalania, are classified under the genus Varanus. There are however zoologists who argue that even these genera, especially Varanus, are overlumped and should be split up. Anyway, the most infamous suggestion from Predatory Dinosaurs of the World was Paul’s decision that Deinonychus, Velociraptor and Saurornitholestes (poor guy gets always left out in these discussions) are similar enough to all be classified under the same genus, which would be Velociraptor, as it was the first one described and its name therefore has priority. Deinonychus antirrhopus therefore became Velociraptor antirrhopus. Perhaps unsurprisingly, there is a nearly direct reference to this in the Jurassic Park novel:

“‘What do you know about Velociraptor?’ Grant asked Tim. He was just making conversation. ‘It was a small carnivore that hunted in packs, like Deinonychus’ Tim said. ‘That’s right’ Grant said ‘although Deinonychus is now considered one of the velociraptors. And the evidence for pack-hunting is all circumstantial.” (Crichton 1990, p. 129).

Earlier in the book Grant also digs up a fossil in Montana, where Deinonychus is found, and identifies it as Velociraptor antirrhopus (p. 46). It is interesting that he mentions the reclassification of Deinonychus like it has become a fact and I actually have seen some people nowadays who seem to think that this was an actual consensus in the 80s/90s and that Michael Crichton was therefore just adhering to the science of the time. Just to be very clear: He was not. Greg Paul was the only person who has suggested this reclassification and it seemed ludicrous to everyone else even back in the 80s, when people were cutting their hair into mullets. The two species not only lived on different continents and showed numerous anatomical differences, but also lived about 40 million years apart. Together with the evidence from above it seems very obvious to me that Crichton renamed his version of Deinonychus purely for dramatic effect and then tried to present Paul’s classification as a popular opinion to give his choice at least a semblance of validity. In-universe that means that Jurassic Park seems takes place in an alternative universe where, against all odds, Paul’s classification won. Or Grant simply has very eccentric opinions. His character, together with his Maiasaura research, is based on Jack Horner after all…
Fig. 4: Deinonychus antirrhopus or what Gregory S. Paul, the illustrator, called Velociraptor antirrhopus. Yes, he illustrated dinosaurs, in fact all small theropods from Velociraptor to Coelophysis, with feathers as far back as the 80s when this idea was still highly speculative, something which I think he does not get enough credit for. This is unfortunately the one major aspect of his paleoart that neither made it into Michael Crichton’s novel nor the movie.
While I do think the most likely identification of the novel raptors is that they are Deinonychus, there are a few discrepancies which might open up a few other possibilities. First and foremost, Dr. Henry Wu, the park’s chief geneticist, identifies at least one of the raptors as Velociraptor mongoliensis (p. 127), not V. antirrhopus, which would be the “correct” name if they were meant to be Deinonychus. However, he was referring to a six week old, small juvenile animal specifically. If the large, adult raptors in the park, which cause a lot of chaos later in the novel, are also classified by the staff as V. mongoliensis is never stated clearly. It could well be possible that they are V. antirrhopus and the juvenile is a new species that has recently been added to the park. This could very well explain why the adult raptors later in the novel eat said juvenile instead of caring for it, as they recognize it is as not being the same species as theirs. A further hint towards this is that near the end of the story we see the raptors caring for their children (p. 434), which makes me doubt that they are meant to be presented as compulsive cannibals. However, what speaks against there being two raptor species in the park is that the juvenile and the adults are described as having essentially the same colouration of a yellow-brownish body with reddish tiger-stripes (p. 130). Later in the novel some raptors are described with dark-green bodies and brownish stripes (p. 433), though it is possible that they are just meant to be the male raptors. The adult raptors who eat the juvenile have also been isolated from the rest of the island’s raptor-population and are therefore more prone to erratic behaviour. Regardless, while it is not outright stated, there does seem to be an insinuation that the park’s geneticists, or at least Dr. Wu, have misclassified the animals. The only concrete reason he cites as to why the raptor is classified as V. mongoliensis is that the amber from which it was cloned came from China (p. 127). This is particularly odd, as V. mongoliensis has so far only been found in Mongolia (Velociraptor osmolskae was found in Inner Mongolia, an autonomous region of the People’s Republic of China, but it has only been discovered in 2008, long after the book was written). A bit earlier Wu talks about how the park’s geneticists do not exactly know what they are cloning from the ambers until it hatches for the first time. This he does while talking about a batch of eggs which he presumes will be “coelurusaurus”, what he thinks is a small herbivore (p. 119). Firstly, while there is a vast dinosaur group called Coelurosauria and a genus named Coelurus, there is no one dinosaur genus actually called Coelurusaurus (there is Coelurusauravus, but that is a small gliding reptile from the Permian). Secondly, if he indeed meant Coelurus or a basal coelurosaur, that would have been a small carnivorous animal similar to Ornitholestes, not a herbivore. Interestingly the name Coelurusaurus is not written in italics, unlike all the other dinosaur names in the novel, so Crichton was perhaps aware of this and was trying to drop a hint at the reader that Wu was mainly a geneticist and not a paleontologist and therefore not very knowledgeable when it came to dinosaur classification. The character even outright states that he is overwhelmed with keeping track of dinosaur names (p. 119). It is therefore still possible that the raptors really are Deinonychus, but are misclassified out-of-universe by Crichton and in-universe by Wu.
Another possible point against the novel-raptors being Deinonychus (or Velociraptor for that matter) could be their size. Though the narration makes them seem about man-sized, as far as I could find their exact size is never mentioned. The head of one of the raptors is however described as being two feet long (p. 130), meaning 60.96 centimeters in non-barbaric units of measurement. At maximum, the skull-length of Deinonychus, the largest known dromaeosaur at the time of the novel, was 41 centimeters, with most specimens only having a length of about 31. Assuming that proportions on the rest of the body are similarly scaled up, the novel-raptors might therefore be nearly twice as large as an average Deinonychus (or were very funny-looking bobble-heads). It is possible that the in-universe explanation for this might have been genetic meddling, growth hormones or simply the benefits of living in captivity in the park. The out-of-universe explanation is, like the name-change, probably dramatic effect. However, if we consider that Crichton read Greg Paul’s Predatory Dinosaurs of the World thoroughly, he would have probably come across this passage:

“Teeth and some slender second-toe bones indicate that a new, small species of Velociraptor was present in the very latest Cretaceous of Western North America. Even more interesting is a tooth of the same age that Malcolm McKenna has at the AMNH: It indicates that a species as big or bigger than V. antirrhopus was alive then, although it seems much less common than the smaller form. Also at the AMNH is a hyper-extendable toe bone from the Late Cretaceous of Mongolia that looks like a Velociraptor far bigger than V. antirrhopus.” (Paul 1988, p. 366).

I unfortunately have never been able to find out much more about the specimens mentioned here by Paul. It seems possible that the large North American raptor tooth might be referring to the very first (and at the time still undescribed/unrecognized) remains of Utahraptor that Jim Jensen found in 1975, though these finds were largely left unnoticed at the time and were stored at the Brigham Young University, not the AMNH (American Museum of Natural History). Utahraptor also lived in the Early, not Late Cretaceous. The large claw, as believed by the blog Dinosaurs on the Silver Screen, could be AMNH 6572, a dromaeosaurid claw collected in 1933 by Edwin H. Colbert in the Iren Dabasu Formation that still remains unclassified. It could not have been Achillobator (a 4.5 to 5 meter long dromaeosaurid from Mongolia that would fit the dimensions of the JP raptors quite well) as many people like to believe, as its holotype was found in 1989 (one year after Paul’s book was published) by a Russian-Mongolian expedition in the Bayan Shireh Formation, stored in the Mongolian National University and was only officially described in 1999. Regardless of what these giant raptor claws were that Paul was referring to, he classified them as Velociraptor and their account may have given Michael Crichton the inspiration and justification to make his novel’s raptors larger than life while still calling them by that name. If Crichton really was basing his raptors on this passage, the JP raptors might therefore unintentionally be neither Velociraptor mongoliens nor Deinonychus, but a species of dromaeosaur that remains unnamed to this day.
Fig. 5: Again Greg Paul’s “Velociraptor antirrhopus”, shown attacking the ornithopod Tenontosaurus. Nowadays it is seen as unlikely that dromaeosaurs like this hunted in packs, with the newest evidence against pack-hunting even coming from a study on tooth-enamel. In general the intelligence of dromaeosaurs has been highly exaggerated in the media thanks to Jurassic Park. In reality their brain-to-body mass-ratio was about on the same level as that of modern ratites, such as emus and ostriches, not parrots or corvids. In all fairness they would have still been among the smartest animals around in their time, though looking at their competition that is not saying much.
As mentioned earlier, Dr. Wu in the novel states that the InGen-geneticists do not exactly know what they are cloning until it hatches for the first time. This very much leaves the possibility open that the company might have cloned animals that (at the time) were unknown to paleontology and were thus unintentionally misclassified (which leaves enough head-canon open for the JP raptors to be a wide number of genera, though without much confirmation). This is something that is never really brought up again in the franchise. The closest thing was a scrapped backstory for the Indominus rex in Jurassic World, which originally did not see it be a hybrid created in a lab, but instead a fictional dinosaur species from China (looking like a mix between Spinosaurus and Carcharodontosaurus, definitely better than the rip-off of the Vastatosaurus from King Kong that we got) that was cloned for the park without any knowledge of what it really was or how it would behave, leading to havoc. It is unfortunate that this sort of risk has never been addressed again, as the large unpredictability of bringing an animal back to life that has never been witnessed by a human being was a major theme in the first novel. It could also explain some of the many inaccuracies that the franchise faces. For example, the movie’s Dilophosaurus (ignorning the anatomically impossible pronated wrists for the moment) is perhaps neither a genetic abomination nor a juvenile (a popular fan-theory even endorsed by Stan Winston), but instead a small dinosaur unknown to science that genuinely possessed a neck-frill and venom glands and, based on the two headcrests, was just misclassified by incompetent InGen-scientists as a mishappen Dilophosaurus. Call it Nublarsaurus, if you will.

The case for the movies

At first it seems that, much like the novel, the raptors in the Jurassic Park movie are actually Deinonychus. First, apart from the fact that they look like how Deinonychus would have been reconstructed in the early 90s, the production team of the movie requested John Ostrom to send them all of his papers and data on Deinonychus. Second, Dr. Grant digs up a “Velociraptor” in Monatana at the beginning of the movie, not in Mongolia. The biggest smoking gun however is that a version of the script from 1991 literally calls them Deinonychus, as does Mark McCreery’s concept art for the movie on which the final designs were based on. Why exactly the name was changed again later is not clear, though it was most likely to make the movie line up more with the novel. Or perhaps it was because Gregory S. Paul literally was one of the scientific advisors on the movie. Of course, we again have the problem that the animals in the movie are a lot larger than either Deinonychus or Velociraptor (in part because in some shots they had to be played by adult men in animatronic suits). Here a common misconception people have is that the large size of the movie’s raptors are based on the then new discovery of Utahraptor and that therefore the JP raptors could be interpreted as actually being that genus. Utahraptor was first officially described and named on the eighteenth of June in 1993, a bit over a week after the first release of the movie. But, like mentioned before, remains of it were known since 1975 (though then largely unrecognized) and the holotype was discovered in 1991 by James Kirkland and Robert Gaston. Nonetheless, it seems that by all accounts the staff working on Jurassic Park were not aware of the discovery until after the size-change was already made. As paleontologist Robert T. Bakker recounts in Raptor Red:

“‘The claw we’ve got- it’s huge!’ I could hear Jim jumping up and down at the other end of the line, and I started jumping up and down too, because I knew something he didn’t. ‘Jim, Jim-Jim!’ I yelled. ‘You just found Spielberg’s raptor.’


‘You just found the giant raptor Spielberg made up for his movie, you know – Jurassic Park.’

Jim thought I was daft. He didn’t know about the other phone call I had gotten about giant raptors that morning. It was from one of the special-effects artists working in the Jurassic Park skunk works, the studio where the movie monsters for Spielberg’s film were being fabricated in hush hush conditions. The artists were suffering secret anxiety about what was to become the star of the movie – a raptor species of a size that had never been documented by a real fossil. No one outside the studio besides me knew about the problem with Spielberg’s giant raptor. No professional dinosaurologist was aware of the supersize raptor being manufactured for the movie. […] The artists doing Jurassic Park wanted the latest info on all the species they were reconstructing. They wanted everything to be right. They’d been calling me once a week for months, checking on the teeth of T. rex and skin of Triceratops. I’d sent them dozens of pages on dino-details. The artists were up to date in their raptor knowledge. They knew that deinonychs were the largest, and that no raptor was bulkier than the average adult male human. Just before Jim called, I’d listened to one artist complain that Spielberg had invented a raptor that didn’t exist. Apparently Spielberg wasn’t happy with the small size of ‘real’ raptors – he wanted something bigger for his movie. He wanted a raptor twice as big as Deinonychus. I’d tried to calm the artist’s misgivings. ‘You know, evolution can change size real fast. It’s not impossible that a giant raptor could evolve in a geological instant. So maybe, theoretically, Spielberg’s oversize raptor could have happened.’ The artist wasn’t impressed with my learned argument. He wanted hard facts, fossil data. ‘Yeah, a giant raptor’s possible – theoretically. But you don’t have any bones.’ But now Jim’s Utahraptor gave him the bones. The fossil beast from Utah turned out to be almost exactly the same size as the biggest raptor in the movie, an animal referred to in the script as the ‘big female’.” (Bakker 1995, p. 3-4.)

We see here that the decision for the upscaling of the raptors’ sizes was made by Spielberg before anyone in the movie’s production had heard of Utahraptor, that the largest dromaeosaur known to them was Deinonychus and that the former’s discovery at best served as a confirmation/justification for the artistic license, not as an inspiration. This is further supported by a famous quote from Stan Winston: “We build it and they discovered it. That still boggles my mind.” While the discovery of Utahraptor was a fantastic coincidence that acted almost like a publicitiy-stunt for the movie (originally the holotype species was even going to be called Utahraptor spielbergi instead of ostrommaysum), the JP raptors are very likely not meant to be Utahraptor for the stated reasons. Not to mention the fact that we now know that Utahraptor was actually quite a bit larger than the JP raptors and a lot more robustly built, almost resembling a mini-‘carnosaur’.
Fig. 6: Deinonychus as it appears in the officially licensed tie-in-game Jurassic World Evolution. Compare with fig. 2. As you can see, in order to differentiate it as much as possible from the franchise’s Velociraptor (itself based on 90s reconstructions of Deinonychus), they made it look like the original Robert Bakker reconstruction from the late 60s and gave it the frills and crests of a basilisk lizard. In my opinion, the better option to make it different would have just been to give it feathers. But hey, I guess if you cannot go forward, you might as well just go even more backwards.
The idea that Jurassic Park takes place in an alternate universe where Deinonychus is classified as a species of Velociraptor and that thus the raptors we see in the movies are actually (artificially oversized) Deinonychus makes sense as long as we just look at the original movies. This has even been a common head-canon among the fanbase for a long time. 2015’s Jurassic World and its accompanying material have however thrown a wrench into that concept. In the movie we can glimpse for a moment at the selection-screen of the hologram display in the Innovation Center and see that it lists Deinonychus and Velociraptor as two different genera (with Velociraptor having its typical JP silhouette). Another image posted on the Dinosaur Protection Group website, created to promote the sequel Jurassic World: Fallen Kingdom, also shows a list of the animals cloned for the park and Deinonychus and Velociraptor are again listed as separate. We never see Deinonychus in the movies (in fact the DPG list implies that it has fallen back into extinction after the events of JW), but it does prominently appear in the accompanying zoo-simulation game Jurassic World Evolution. Here it looks radically different from the JP Velociraptor, not only being smaller but also resembling the original 1969 reconstruction by Robert Bakker, though bizarrely adorned with a crest and fin along the head and tail meant to make it resemble a basilisk lizard (which when you really think about it is a slap in the face of the dinosaur’s importance to paleontological history, as it was the animal that destroyed the idea of dinosaurs just being big lizards and it revived the bird-dinosaur link). From the same game we have a little titbit of information on the Velociraptor (fig. 7) which clearly states that the InGen geneticists have accidentally recreated the dinosaur much larger than its real-life counterpart. In the game you can find the dinosaur’s fossils in the Iren Dabasu and Flaming Cliffs Formation (the same by the way goes for the game’s predecessor Jurassic Park: Operation Genesis from 2001), again not the Bayan Shireh Formation where Achillobator is found. This implies that the classic JP raptors really are meant to be Velociraptor mongoliensis, the turkey-sized, feathered ground-hawk, but have been unintentionally genetically altered to the point where they do not resemble their originals anymore at all. This would actually fit with some lore pieces which state that Velociraptor was one of the first, if not the first dinosaur recreated by InGen, meaning it likely still had a lot of genetic kinks that needed to be worked out. Of course, this version of events may just pertain to the canon of the game (which does play in one or more continuities different from the main movies), though together with the information on the DPG website, the holoscape seen in the actual movie, and the fact that the developers closely worked with Universal and the production teams of the movies, this really does seem to be the explanation used behind the scenes and which we might regard as canon…
Fig. 7: You would think that after being the cause for so many deaths, the park’s geneticists would finally fix the genome and make the animal smaller. Does Joe Exotic happen to work for InGen?
…if it were not for one major problem: In the first movie Dr. Grant digs up a fossil, which looks exactly like the JP raptors and which he definitely classifies as Velociraptor, IN MONTANA. If the JP raptors are really meant to be overgrown Velociraptor mongoliensis and Deinonychus exists in this universe as its own separate genus, then this makes absolutely no sense. Perhaps Alan Grant really is just a Jack Horner/Greg Paul-type eccentric who personally classifies Deinonychus as a species of Velociraptor and goes against general consensus, but this idea quickly becomes unfeasible if we take into account that both the InGen staff and Tim Murphy independently from him also classify the raptors in the movie as Velociraptor, not Deinonychus. Assuming that, somewhen between Jurassic Park III and Jurassic WorldDeinonychus was recognized as a separate genus in the film’s universe also does not help, as the raptors we assume to be misclassified Deinonychus are still called Velociraptor by everyone in the newer movies. Retconning the classic JP raptors from being V. antirrhopus to actually being V. mongoliensis would create a continuity problem which could not simply be explained through frog-DNA. The same goes by the way for the novel. For my own brain’s wellbeing I will therefore still maintain that in the Jurassic Park universe Deinonychus is classified as Velociraptor antirrhopus and that the raptors we see in the movies are this species, albeit heavily modified through genetic engineering. Apart from a very quick and easy to miss detail in Jurassic World, any evidence that Deinonychus exists as its own genus in the JP universe comes from extended material like videogames and websites, which are regarded as soft-canon at best, and can therefore be easily dismissed if one wishes to do so.
Fig. 8: A promotional image from the Dinosaur Protection Group’s website. Deinonychus and Velociraptor are listed as separate genera, with the red marking implying that Deinonychus has fallen back into extinction. Metriacanthosaurus got the shaft too.

As a final discussion point, let us turn to the raptors which appear in Jurassic Park III. These are different from the raptors we see before and after the third movie in many details: Their coloration is different, their heads are more elongated and pointier, they have prominent crests in front of their eyes and the males possess feather-quills on top of their head. Their origin and relationship to the other raptors is never explained in the movie. Out-of-universe their design-change was simply meant to be a sort of retcon, as it had become undeniable by 2001 that dromaeosaurs had feathers (unfortunately this did not translate into the following sequels due to the movie’s unpopularity). The closest thing to an official explanation we got was an interview from John Rosengrant, in which he said that these are the same raptor species as the one we see in the previous films, but they have somehow evolved further in the isolation of Isla Sorna. This, however, seems very unlikely, as evolution does not work like that in a span of just four years. Given how this movie establishes that InGen has created dinosaur species which were not officially listed in their documents, such as Spinosaurus, and that it plays in the previously unseen Northern part of Isla Sorna, it becomes tempting to speculate that these raptors might be a different species than the ones we see in the other movies. Could this be Jurassic Park’s version of Utahraptor or Achillobator? While that would be a cool explanation, there are a couple of things going against it. Firstly, in the in-universe InGen leaks on the DPG website, no new dromaeosaur species is listed among the dinosaurs which Dr. Henry Wu illegally created on Isla Sorna between the second and fourth movie. It is just Spinosaurus, Ceratosaurus, Corythosaurus and Ankylosaurus. The best thing we have is this internal memo by Wu, which can be found on the Masrani backdoor website (again created to promote Jurassic World):




DATE: 02/20/2003 1410 CST



This is ambiguous enough to interpret that the raptors we see in Jurassic Park III are a failed experiment by Wu to faithfully recreate dinosaurs with feathers, explaining the sparse quills on their heads, but the wording strongly implies that his efforts to make feathered dinosaurs and his gene-splicing tests on Sorna are two different things. That makes it far more likely that what is meant with the “accident” on Sorna is in fact the Spinosaurus, which due to its numerous inaccuracies and ridiculous capabilities is now often regarded as an early experiment by Wu into dinosaur-hybridisation. While it is still possible that the quilled raptors were created by Wu during his illegal cloning adventures on Isla Sorna, there is no in-universe documentation of this. They could just as well have been made by InGen back in the early 90s when Jurassic Park and the facilities on Sorna were still operational. In either case, it seems the most likely that they were genetically altered/improved versions of the previous raptors, not a new species. If they were created when Jurassic Park was still operational it is possible that they were even meant to eventually replace the 93’ variant before Sorna was abandoned, as they not only seem a lot more intelligent, but are also at least somewhat cooperative and less hostile to humans, as we can see by the ending of JPIII. The idea to genetically alter the dinosaurs to be more docile and continually replace them with “updated” versions is something mentioned in the franchise as early as the first novel. The semblance of feather-like structures on their bodies could also imply that their DNA is somewhat more authentic to the real animal than in the previous variants. The idea that they are essentially the same species as the other raptors is also supported by the ending, in which Grant manages to communicate with the raptors by using a 3D-printed resonance-chamber, which he scanned from a “Velociraptor” he dug up again in North America. The quilled raptors are therefore most likely also meant to be Deinonychus/Velociraptor antirrhopus, just a genetically more (or less) altered variant than the other ones we see.
Fig. 9: May the real Deinonychus please stand up?
Long story short, while the real-life Velociraptor mongoliensis is a fascinating and cool animal in its own right (as is really any dinosaur to be honest), because of Jurassic Park it has been stealing the limelight from Deinonychus for nearly three decades now. This was not helped much by speculations that these movie raptors are actually Utahraptor or Achillobator, the confused mess of a lore that has been created by spin-off material and the movies’ own disabilities to properly explain what their raptors actually are. I somehow suspect that we will never get a real confirmation that the raptors are actually Velociraptor antirrhopus/Deinonychus in the movie canon, as most modern audiences, especially younger ones, will have no idea about the weird history of 1980s paleontology that led to this bizarre chimaera of a film-creature, so it is best left vague as to not open up too many questions. As we have seen, there have even been mild attempts at retconning their original identity, though these would create even bigger problems to explain. Without any real confirmation probably ever coming out, I just want to stress here at the end that this post is just my personal (though hopefully well-argued) theory and you are free to speculate about the identity of the JP raptors all you want. And hey, lately there have been rumours that the upcoming third film of the new trilogy, Jurassic World: Dominion, will feature not only new but also a lot more scientifically accurate dinosaurs, likely produced by rival genetics companies. Perhaps this will be the time to shine for Utahraptor and Achillobator, hopefully with feathers that will make them look like giant, toothed harpy eagles.

Related Posts:
Literary Sources:
  • Bakker, Robert: Raptor Red, New York 1995.
  • Crichton, Michael: Jurassic Park, New York 1990 (2015 reprint).
  • Paul, Gregory Scott: Predatory Dinosaurs of the World. A Complete Illustrated Guide, New York 1988.
  • Schalansky, Judith: Die Verlorenen Welten des Zdeněk Burian, Berlin 2013 (Naturkunden 8).
Online Sources/Further Reading:
Image Sources:
  • Fig. 1: Schalansky 2013, p. 53.
  • Fig. 2: Ostrom 1969.
  • Fig. 3: Paul 1988, cover.
  • Fig. 4: Paul 1988, p. 172.
  • Fig. 5: Paul 1988, p. 367.
  • Fig. 6-7, 9: Jurassic World Evolution, developed by Frontier, copyright Universal. Images taken by me using the Playstation 4's capture mode.
  • Fig. 8: The DPG website

Thursday, 7 May 2020

The Alien Prehistoric World Trope: Part 5 - Renaissance Madness

This is part 5 of an ongoing series (for the previous one go here), but I think it can be read perfectly fine on its own.
Fig. 1: The first reconstruction of Deinonychus with commentary by Adrian J. Desmond. It is the prototype for how the public imagines dromaeosaurs: An ugly, leathery skin, an unfeeling, lizardine face, zombie-arms and fast as hell. While today this seems very outdated, it was revolutionary at the time.

Beginning in the late 60s it was finally realized that dinosaurs had been misinterpreted by paleontologists for many decades. It arguably began in 1964 when John Ostrom reanalysed the dentition, anatomy and gut-contents of hadrosaurs and came to the conclusion that the dogma of them being aquatic duck-mimics was entirely mistaken. He was able to show that they were fully terrestrial animals capable of chewing on a wide variety of plants and that they likely occupied the same ecological niches as large ungulate mammals do today. The ultimate paradigm shift came however when Ostrom described Deinonychus in 1969. This dinosaur’s anatomy was entirely unlike anything expected from a dinosaur at the time, as it was clearly an animal made for running fast, jumping and slicing. This could not have been a cold-blooded reptile. Moreover, its anatomy was remarkably bird-like, to the point where Deinonychus is best described as an overgrown version of Archaeopteryx. This led Ostrom to revive the idea that birds directly descend from dinosaurs, first proposed by Thomas Henry Huxley but refuted by Gerhard Heilmann since the 1920s. Ostrom’s student, Robert Thomas Bakker, reanalysed various other dinosaur groups and came to the realisation that there was something seriously wrong with our image of every single dinosaur group. Sauropods could not have been swamp-dwellers, as their lungs would have collapsed if they were fully submerged in water, stegosaurs and ceratopsians did not have sprawling forelimbs, as trace-fossils could attest, and theropods were not mindless eating-machines but had fairly sophisticated bird-like brains, just to name a few examples. Most importantly, if dinosaurs were inferior to mammals, as was often thought, why were they capable of competing them out of every single large animal niche for nearly 160 million years? Dinosaurs were not cold-blooded reptilian creatures like lizards and turtles, but warm-blooded, bird-like creatures. Ostrom and Bakker started what we today call the Dinosaur Renaissance. It is called a renaissance as they revived many ideas which had already been proposed in the late nineteenth century but were subsequently forgotten due to a lack of interest in the field or serious malpractice (See part 2).
Fig. 2: A very bizarre Allosaurus, as drawn by John C. McLoughlin in 1979. Take notice of the subtle, mammal-like facial features.
This paleontological revolution was new, exciting, important, brought us closer to how these animals really were like and it did away with the old idea that everything in the past must have been primitive. But here I argue that the period from the 70s to the early 2000s also brought with it a serious image problem for the dinosaurs, perhaps being one of the largest contributors to the Alien Prehistoric World Trope. While dinosaurs were not seen as weird mega-lizards anymore, like in the preceding decades, they were now seen as almost entirely alien animals. First and foremost, this began with the new classification schemes laid down by Bakker, Desmond and others. Throughout the Dinosaur Doldrums, the different dinosaur lineages were seen as unrelated groups of large archosaurs that independently arose from a stock of primitive “thecodonts”, meaning that dinosaurs were an unnatural grouping. Bakker saw however that all these groups share many anatomical characteristics and must have all descended from a single ancestor, making Dinosauria a natural group again. This was a time before cladistics and phylogenetic classification became popular, so most paleontologists were still working with ranked taxonomy, which largely does not classify animals by their relatedness, but by their physical characteristics. Seeing how dinosaurs lacked many of the characteristics by which reptiles were usually defined, he and Peter Galton therefore chose to lift them out of this group and make Dinosauria its own vertebrate class, on the same level as Mammalia, Reptilia or Amphibia (Birds/Aves were demoted from being their own class to being a subclass of Dinosauria). What actually constituted Dinosauria was a matter of some debate. Bakker included pterosaurs inside Dinosauria, while Adrian J. Desmond argued that they also should be their own vertebrate class. Others like Gregory S. Paul and John C. McLoughlin instead argued that Archosauria as a whole (the group that includes crocodilians, dinosaurs/birds and pterosaurs) should be promoted to its own class instead, with Dinosauria and Aves just being subclasses of Archosauria.
Fig. 3: With the Dinosaur Renaissance we also enter the age of shrinkwrapping and Gregory S. Paul-style reconstruction. Our old friend, the fog of time, is also gone.
As we will see in a future part, this whole discussion has become obsolete nowadays thanks to phylogenetics (dinosaurs still are reptiles, despite being warm-blooded, and birds are both dinosaurs and reptiles), but it left a clear impact on our perception of dinosaurs. In this view, dinosaurs were, of course, not mammals, but neither were they reptiles and most were not birds either. They went from being large, but comprehensible reptiles to being chimaeric creatures that occupied the same ecological niches as mammals do today while looking very different. Dinosaurs became their own weird thing. They were essentially aliens. From this time we have quotes such as this one by Walter Coombs:

"Sauropods are basically alien animals . . . What can be said of the habits of an animal with the nose of a Macrauchenia, the neck of a giraffe, the limbs of an elephant, the feet of a chalicothere, the lungs of a bird, and the tail of a lizard?" (Coombs 1975).

A bizarre trend in paleoart from this time is also the attempt to deny dinosaurs any reptilian characteristic, instead giving them a somewhat more mammalian appearance. This was mostly because modern reptiles were seen as “lower vertebrates” and had a lot of negativity associated with them, mainly due to cultural reasons. Dinosaurs, being warm-blooded instead had to be “higher vertebrates” like mammals and therefore must have looked and acted accordingly. John C. McLoughlin’s art is a great example of this, as he tended to give theropods quasi-mammalian facial tissues, gave his ornithopods goat-like slit pupils and infamously depicted ceratopsians with a fatty hump akin to a bison’s. Around the same time Robert Bakker, Walter Coombs and others proposed the possibility that sauropod dinosaurs may have given live birth and maybe even had elephantine trunks on their face. Many books from this time also liken ornithopods to gazelles. A lot of dinosaurs were depicted with leathery skin similar to that of elephants or rhinos, instead of scales, and only few artists dared to give them bird-like plumage as such a thing was still very speculative. The dinosaurs were mostly denied the association with both their ancestry and their progeny in order to drive the point home that they were just as capable as mammals, regardless of how weird the reconstructions ended up looking. In addition to this, a new paleoart trend began to appear which we today call shrink-wrapping. To accentuate their dynamicity, but to also brag about one’s anatomical knowledge, paleoartists seriously slimmed down their dinosaurs to the point where the skin was just tightly wrapped around the bones and muscle with little else and the contour of much of the skeleton became visible. This produced images of very skeletal, almost undead-looking dinosaurs and it seemingly took decades until some people pointed out that barely any animal alive today looks like this unless it is starving. The end-result of all of this was an image of dinosaurs that roughly goes like this: Dinosaurs were a unique group of animals on the same level as mammals but essentially alien to us that had uncomfortable, leathery skin and a zombie-like appearance while still being powerful and fast. That sounds intimidating, does it not? More importantly it sounds unreal and very otherworldly.
Fig. 4: The Dinosaur Renaissance was also a time of very bizarre theories. On the left we see John C. McLoughlin’s (vehemently held) vision that the neck-frill of ceratopsians was actually the base of a muscular hump. On the right we see Robert Bakker speculating about a prehensile trunk in the sauropod Diplodocus. To his credit, while he considered the possibility, he did not take it as seriously as others. He did however come up with the idea that sauropods gave live birth like elephants.
With the Dinosaur Renaissance we also saw the resurgence of (perhaps subconscious) beliefs about antediluvian times, namely the return of catastrophism. Prior to the Renaissance it had been believed that dinosaurs gradually went extinct due to outcompetition from mammals, the evolution of new plant-types or gradual climate change. However, the Renaissance showed that the dinosaurs could not have simply been wiped out by slow, gradual change and instead evidence was amounting that a catastrophic event happened that no large animal, no matter how advanced, could have survived. Massive volcanism or even the explosion of a nearby star were theorized as causes for some time. Then in 1980 the smoking gun was found by Luis Alvarez and his son Walter in Gubbio, Italy. Here they analysed the geologic boundary between the end of the Cretaceous and the beginning of the Paleogene and found unnaturally high amounts of iridium. Similar findings were subsequently reported from all around the world at the same boundary. Iridium is rare on Earth, but common in asteroids. The most likely explanation for this high amount of iridium in such a short time must have been one or more major impact events. That this coincided exactly with the extinction of the dinosaurs could not have been a coincidence. The Alvarez Hypothesis was however not taken seriously at first, even by proponents of the Dinosaur Renaissance (if you recall that one scene from Jurassic Park where Tim nerds out to Dr. Grant you might remember that Bakker was in favour of diseases being the cause for the extinction, though that’s a high simplification of his argument). The reason was that the prevailing view of geology at the time was still gradualism. Catastrophic events of biblical proportions, such as asteroid impacts, simply did not happen in Earth’s history according to this view. This changed in 1991 when underneath the Caribbean Sea and the Yucatan peninsula the Chicxulub Crater was found, which fit the size and age of the sought impactor perfectly. Further evidence came in 1994, when the 1.8-kilometer-wide comet Shoemaker-Levy-9 was observed breaking up into multiple pieces and crashing down into Jupiter’s atmosphere, leaving the cloud-layer with a visible “scar” for many months. This was the ultimate proof that catastrophic impacts do and did happen on a cosmic scale and that they had an impact on life on Earth. As astrophysicist and planetologist David H. Grinspoon recounts, there was a brief period of time afterwards where nearly every astronomer tried explaining almost every feature of our neighbouring planets through massive impacts. This “neo-catastrophism” brought with it also the rebirth of public imaginations about how the past is structured (see part 1). Similarly to Victorian times, where it was believed the world of the dinosaurs, ancient mammals and primitive humans was separated from today by the deluge of the Bible, we now had a massive catastrophe again that separated us from prehistory not only temporally but also physically. Dinosaurs were not only an alien group of animals but they lived in their own alien world that was destroyed to create ours. A rarely mentioned factor that likely also added to the Alien Prehistoric World Trope is the fact that the idea of plate tectonics had only just been accepted a couple of years prior. While Alfred Wegener had proposed the idea of continental drift back in 1912, he was not taken seriously until scientific revolutions in the late 50s and 60s (the actual age of the Earth and the dinosaurs also was not known until the late 50s if you recall part 3). If you read older dinosaur books like All About Dinosaurs by Roy Chapman Andrews from 1953, you will see that it was still thought back then that the dinosaurs lived on continents with largely the same shape and position as today (Andrews 1953, p. 10). The somewhat disturbing realization that the very continents we stand on were in different places in deep time and looked different was made only shortly before the Dinosaur Renaissance kicked off and helped shape an image of the past as an even more foreign land.
Fig. 5: Around the same time the Dinosaur Renaissance was going on, the bizarre animals of the Cambrian were being re-evaluated and entered the public consciousness thanks to the debates started by Stephen Jay Gould.
Not only did dinosaurs become alien in the wake of the Dinosaur Renaissance, they also became scary. Of course, dinosaurs have always been used as scary movie monsters since the time the general public got to know about them (see part 2), but that was because they were simply strong, mindless brutes. Thanks to the Renaissance, dinosaurs became scary on a deeper, psychological level. Around the same time as the advances in dinosaur science were being made, a major revision of the Burgess Shale and other Cambrian fossils occured. When the animals of the Cambrian, themselves over twice as old as the oldest dinosaurs, were first discovered in 1909, they were originally shoehorned into known animal phyla and seen as primitive ancestors of those groups. A revision done in the 70s had however shown that while some genuine ancestral forms did exist in the Cambrian Burgess Shale, the great majority of the animals were wrongly classified and in fact looked so weird and bizarre that they were unable to be classified into any known animal groups. Creatures like Opabinia, a multi-finned segmented animal with five eyes and a clawed trunk, or Hallucigenia, a worm-like creature with stegosaurusesque spikes on its back and tentaculate legs, were probably also contributors to the Alien Prehistoric World Trope as they looked like they came straight out of Star Wars. More significant however was their importance for evolutionary history. As Stephen Jay Gould observed in his book Wonderful Life many of these bizarre forms were not primitive, but already highly sophisticated and specialized forms that lived alongside the ancestors of modern animal groups without being inferior to them. The reason why the oddballs went extinct and the ancestors of our known animal groups survived seems to have been purely up to good or bad luck. With this, Gould demonstrated the importance of coincidence in evolutionary history and argued against orthogenesis, the idea that evolution is goal-oriented and inevitably would have produced humans (a view still prevalent into the late 20th century). If things during the Cambrian went just a little bit different, the descendants of the bizarre Cambrian forms might now rule the Earth instead of chordates and arthropods. Similarly, he argued, the Dinosaur Renaissance and the Alvarez Hypothesis have shown that the dinosaurs were such a successful and adaptable group that it took a random catastrophic event to wipe (most of) them out, not some supposedly superior mammals. The scary thing for many people about this is the thought that if the asteroid by coincidence had missed the Earth, the dinosaurs would in all likelihood still rule the Earth and would have bullied our mammalian ancestors further into submission or even extinction.
Fig. 6: Dale Russell’s Dinosauroid as drawn by John Sibbick.
Humans, at least as we know them, would have never evolved. This existential dread is further cemented by the idea that dinosaurs might have even been able to replace our “role” in the world. A big idea of the Dinosaur Renaissance was that not all dinosaurs were simple, mindless dullards. Many new coelurosaurs, such as ornithomimids and dromaeosaurs, were discovered and their braincases showed that their brain-sizes were comparable to those of modern birds rather than reptiles. In hindsight the brain-sizes of these dinosaurs were greatly exaggerated, their intelligence was probably more comparable to that of ratites (ostriches and emus) rather than those of crows or parrots and the mental feats we see in movies like Jurassic Park are unlikely. However, these comparatively still brainy dinosaurs allowed the imagination to go wander. This famously led to a thought experiment by Dale Russell in which he imagined what Troodon (today generally classified as Stenonychosaurus), the most brainy dinosaur known at the time, would look like today if the extinction at the end of the Cretaceous never happened. The end-result was the now infamous Dinosauroid which you have probably seen if you ever owned a dinosaur-book between the 80s and the 2000s. The most striking thing about it is that it looks uncannily human, as it stands on plantigrade feet with an upright spine and lacks a tail. Probably by coincidence Russell also made it look how we generally imagine a generic alien to look like. I believe we can all agree that with its naked, green skin, large eyes and bulbous head, the Dinosauroid could just as well stand on the surface of Mars or sit in the background of the Mos Eisley Cantina without looking out of place. Science fiction writers and conspiracy hacks were quick to notice and soon after the reveal of the Dinosauroid, sci-fi stories began to appear where putative alien species turn out to actually be evolved dinosaurs that invented space travel before the asteroid hit. The most prominent examples are probably Star Trek Voyager and Doctor Who. At around the same time there were conspiracy theories that real-life sightings of aliens and reptilian humanoids might be descendants of this Dinosauroid. The idea of dinosauroids became a popular trope in science-fiction and paleoart and likely had a great influence on people’s mental connection between dinosaurs and extraterrestrial life. As we have seen in Part 2 of this series, the idea of extraterrestrial or spacefaring dinosaurs also already had precedent in older movies and novels.

Fig. 7: The original Dinosauroid model by Dale Russell and Ron Seguin. 
Nowadays it probably goes without saying that the idea of the Dinosauroid is highly improbable. This very humanoid look was argued for by Russell mainly through circular reasoning as he had a very anthropocentric and orthogenic bias, probably due to his religious beliefs. For example, he argued for an upright stance so that the large head would be balanced out better, but this ignores the fact that even in very big-headed dinosaurs like T. rex this job was already perfectly done by the large tail. The only reason why we humans stand and walk with a vertical spine is because our ape-ancestors had lost their tails due to arboreal specializations. Troodon and its descendants would not have had that problem and a big-brained dinosaur would in all likelihood still walk with a horizontally held spine like all dinosaurs before it. The most important factor ignored by Russell is that Troodon, his basis for the speculation, was in nearly all anatomical characteristics basically just a big flightless bird. As Gregory S. Paul recounts:

The concept garnered much publicity and for Russell much friendly abuse from other dinosaurologists. That tabloids cited Russell’s work as confirmation that, among other things, dino-humans are reemerging from the ground in certain midwestern states has not helped! There are serious problems with the idea. Troodont brains were only about the size of ostrich brains, or a little bigger. They were not anywhere comparable to the much larger and more sophisticated brains of primates. Nor were theropod fingers the fine-tuned grasping organs of primates. Whether troodonts would ever become intellectual tool users is dubious, though not totally impossible. As for the postulated troodont “hominoid” itself, the model Russell and Sequin made looks suspiciously human with its lost tail and vertical body. One might expect a more theropod-like or birdlike horizontal posture, with a tail sticking out behind. What bothers me is that the dino-homonoid speculation diverted public attention from what is really important about troodonts. These dinosaurs were more bird-like than Archaeopteryx, and were part of the initial bird radiation. They were not pseudo-human.” (Paul 1988, p. 397).

That last part Paul addresses is in my opinion one of the most important factors of dinosaur-imagery from this period as a whole. While many paleontologists like Ostrom, Bakker and Paul went to great lengths to point out the remarkable similarity and continuity between non-avian dinosaurs and birds, this was rarely the focus of popular paleoart and media at the time. The news instead always read something like “Dinosaurs were warm-blooded!”, “Dinosaurs were superior to mammals!”, “Dinosaurs could do this and that!” and so on. The 70s and 80s were the Wild West of bizarre dinosaur speculations, with some people seemingly throwing as much weird stuff on the wall as possible to see what sticks. The focus was put on how new and exciting, weird and bizarre dinosaurs now were and how they compared to mammals, but not on how similar many of them were to the avian dinosaurs still around today or that these were real animals that once existed. This was because dinosaurs still had to fulfil a certain role in the public imagination, which was that of the movie monster that could chase the protagonist around. When people think of Jurassic Park they remember the scenes where the T. rex runs after a jeep, where the Velociraptors can open doors or where the Dilophosaurus spits venom. Rarely do they remember the actual end of the movie and its deeper meaning: Alan Grant, with Hammond’s grandchildren in his arms, escapes with the others by helicopter from the island. As they fly over the ocean, Grant looks out the window and sees a flock of pelicans majestically flying over the water. He looks on wistfully. The things that chased him around in the park were just theme-park monsters made for entertainment. He realises that the real, living dinosaurs are those outside the window.
Fig. 8: One of the perhaps most compelling dinosauroids and it is not even a dinosaur. This illustration was produced by Wayne Barlowe for a story that tied into West of Eden, a sci-fi series by Harry Harrison in which a species of intelligent mosasaurs, the Yilane, take over Earth after the End-Cretaceous asteroid misses. 

For the next part in this series we will focus on just a single artist that embodied the Alien Prehistoric World trope like no one else: Wayne Douglas Barlowe. See you until then.

Related Posts:
Literary Sources:
  • Andrews, Roy Chapman: All About Dinosaurs, New York 1953.
  • Bakker, Robert Thomas: The Dinosaur Heresies. New Theories Unlocking The Mystery of the Dinosaurs and Their Extinction, New York 1986.
  • Barlowe, Wayne: The Alien Life of Wayne Barlowe, Beverly Hills 1995.
  • Barrett, Paul/ Naish, Darren: Dinosaurs. How they lived and evolved, London 2016 (Second Edition).
  • Brusatte, Steve: The Rise and Fall of the Dinosaurs. A New History of a Lost World, New York 2018.
  • Conway, John/Kosemen, C.M./Naish, Darren: All Yesterdays. Unique and Speculative Views of Dinosaurs and Other Prehistoric Animals, UK 2012.
  • Coombs, W. P. 1975. Sauropod habits and habitats. Palaeogeography, Palaeoclimatology, Palaeoecology 17, 1-33.
  • Desmond, Adrian: The Hot-Blooded Dinosaurs. A revolution in Paleontology, London 1975.
  • Gould, Stephen Jay: Wonderful Life. The Burgess Shale and the Nature of History, New York 1989.
  • Grinspoon, David Harry: Venus Revealed. A New Look below the Clouds of our Mysterious Twin Planet, Cambridge 1997.
  • Mcloughlin, John: Archosauria. A New Look at the Old Dinosaur, New York 1979.
  • Norman, David: The Illustrated Encyclopedia of Dinosaurs, New York 1985.
  • Paul, Gregory Scott: Predatory Dinosaurs of the World. A Complete Illustrated Guide, New York 1988.
  • Witton, Mark: Recreating an Age of Reptiles, Marlborough 2017.
  • Witton, Mark: The Paleoartist's Handbook. Recreating prehistoric animals in art, Marlborough 2018.

Online Sources/Further Reading:
Image Sources:
  • Fig. 1: Desmond 1975, p. 76.
  • Fig. 2: McLoughlin 1979, p. 51.
  • Fig. 3: Paul 1988, p. 56.
  • Fig. 4 left: McLoughlin 1979, p. 87.
  • Fig. 4 right: Bakker 1986, p. 141.
  • Fig. 5: Gould 1989, p. 126.
  • Fig. 6: Norman 1985, p. 55.
  • Fig. 7: Russell 1982.
  • Fig. 8: Barlowe 1995, p. 24.