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Science Marches On / Walking with Dinosaurs

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While Walking With Dinosaurs was generally accurate for when it was made, it's around two decades old now. New evidence regarding behavior, color and other details are always emerging. So, there are inaccuracies.

Walking With Dinosaurs

In general

  • Most coelurosaurs certainly had feathers. The several dromaeosaurid species surely had them, but in the franchise they are all shown featherless: this, rather than Science Marches On, might be interpreted more as Rule of Cool, or rather, Artistic License – Paleontology, since feathered raptors would have appeared "too cute"? In Real Life dromeosaurids had WINGS just like their famous relative, the "ur-bird" Archaeopteryx… This might be nothing compared to what is seeming to come: most small-sized dinosaurs may well have had some sort of covering. This is a very recent theory led by the discoveries of the primitive herbivore Tianyulong in China and Kulindadromeus in Russia, and further supported by the discovery of feathers or feather-like filaments in two anurognathid pterosaur specimens from China: the theory is that some kind of covering was present in the last common ancestor of all dinosaurs and pterosaurs, and then it was partially lost by its largest descendants, possibly because of the surface area to volume ratio. Some think the "spikes" on Diplodocus have the same common origin of feathers, as well as the quill of the small herbivore Psittacosaurus and even the horny bumps lined on the back of several hadrosaur mummies. See Dinosaurs for more infos about that. Whatever the case, the old "gigantic lizards" seem to have their days numbered now.
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  • While the pterosaurs are correctly portrayed with pycnofibers, in all cases this is very sparse and in the CG models, basically nonexistent. In reality, it's probable that pterosaur pelts were equal in density to typical land mammals (such as bats), and most species would have been very noticeably fluffy/furry. For instance, compare their Anurognathus to a modern reconstruction.
  • They tried to partially remedy all the issues by showing Walking with Dinosaurs again in 2008 with updated narration. Unfortunately, the visuals remained untouched, so the small carnivore Ornitholestes still had a horn, coelurosaurs were still scaly, so on and so forth.
  • Any and all shots of pterosaurs taking off bipedally became inaccurate after it was discovered that they launched quadrupedally. The documentary also avoids showing the large pterosaurs taking off almost entirely, because at the time it was uncertain how such large flying animals could lift up from the ground. It's now known that they probably pushed off their front limbs to vault themselves into the air.
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  • All the non-avian theropods have pronated hands, a position that is impossible in reality, instead they held their hands out to the sides, akin to their relatives the birds.
  • Pterosaurs wings have two major problems- one, they all come to an acute point, while we now know that many of the larger families would have had rounded wings, and when landed the wings folded outward like an origami crane, as opposed to the (rather complicated and hard to model) way the folded inwards and behind the animal's arms.


New Blood

  • What was thought to be evidence for "cannibalistic Coelophysis" has been discredited. Some of the evidence was cannibalism was later seen as adult Coelophysis simply having died on top of juveniles, while the stomach contents of other adult Coelophysis was determined to be that of small crocodilians, not younger Coelophysis.
  • As the now-synonymous Megapnosaurus indicates, Coelophysis was nocturnal.
  • The early long-necked dinosaur Plateosaurus could not walk on four legs.
  • The pillar-limbed croc-relative Postosuchus was most likely a biped, or at least semi-bipedal, rather than an obligate quadruped. It would be a pursuit predator, not a slow ambush predator. However, it does rear up on its back legs in the episode for brief moments.
  • There were no cynodonts of the size depicted in the program in the late Triassicnote . This is an example of Science Marches On rather than Artistic License – Paleontology because at the time the series was produced it was assumed that cynodonts of that size did live in Late Triassic in North America. This assumption was based on the discovery of two teeth from Chinle Formationnote . However, post-WWD study indicates that these teeth can't be confidently referred to Cynodontia (or any other known group of Triassic amniotes, for that matter).
  • The youngest known dicynodont is not considered Placerias anymore, with the Polish Lisowicia known from slightly later deposits (roughly eight million years younger). There's also (extremely dubious) remains of possible dicynodonts from the Early Cretaceous of Australia, but they're very scrappy and their assignment to dicynodonts is tentative at best. A reexamination of the remains has confirmed that they were not even dicynodonts at all, or even from the Cretaceous, they were actually diprotodont marsupials from the Pleistocene epoch.

Time of the Titans

  • Allosaurus was only one-fourth the size it was depicted. This may have resulted from confusion with a close relative called Saurophaganax which actually did grow to 6 tons. However, some scientists do consider the two to be the same animal (although still as a separate species, Allosaurus maximus, as opposed to the species most are familiar with, Allosaurus fragilis).
  • The idea that Ornitholestes had a nasal crest was based on the fact that post-mortem damage to the type fossil had warped the bones of the snout upwards. In Real Life, their noses were almost certainly unadorned.
  • Recent studies suggest that Anurognathus and its ilk were nocturnal and caught insects on the fly, like bats or swifts, making the "Mesozoic oxpecker" idea presented on the show highly unlikely (and that's not even mentioning that Anurognathus isn't even known from the same continent as Diplodocus).
  • Post-WWD studies indicate that sauropod dinosaurs probably didn't grow to adult size within more or less ten years as shown in the series, although exactly how fast they grew is still debated (current estimates range from less than four decades to up to 70 years of growth necessary to reach maximum adult size).
  • The idea that most sauropods (brachiosaurids such as Brachiosaurus being the exception) could only hold their necks horizontally - which influenced the WWD reconstructions of Diplodocus, Apatosaurus and Argentinosaurus, which in turn probably popularized the concept - is questioned nowadays as well.
  • "Iguana-spike-backed" Diplodocus: Some researchers now argue these spikes were spread across on Diplodocus' back rather than put in a single line as shown in the program.
  • Footprints from a baby bipedal sauropod have been recently found: Perhaps Littlefoot and the WWD sauropodlets walked on two legs and become quadrupedal only when they grew larger (an ancient heritage from their ancestors, the "prosauropods" such as the aforementioned Plateosaurus)! However, most paleontologists are skeptical of this interpretation. Even the trackways of adult sauropods often leave just the prints from just one pair of feet, thus is even more likely about the younger ones.
  • Brachiosaurus is no longer considered the largest land animal; the exact species of sauropod that was is not clear, one such candidate being Argentinosaurus, but it wasn't Brachiosaurus.
  • The sauropods are depicted with nostrils on their foreheads (this was because the nasal openings on the skull were located there, so it was assumed the nostrils were there as well), but nowadays a position near the tip of the snout as with most dinosaurs is considered far more likely (it was later pointed out that in all land vertebrates the nostrils were located in front of the bony nasal openings and not on them).
  • Evidence suggests that Stegosaurus lived in herds and would have preferred the open savanna regions of the Morrison formation to the more forested areas. Also, a recently-discovered skin impression of Hesperosaurus has shown stegosaur plates were covered in horn rather than skin.note  So much for the scene where the Stegosaurus changes the color of its plates by flushing blood into them. And then in 2014 came "Sophie", the most-complete specimen of Stegosaurus to date, which revealed that Stegosaurus's neck and tail were longer than previously thought, the hindlegs were slightly shorter, and the tip of its tail pointed downwards.
  • Another that was speculative to begin with: The idea that dung beetles coevolved with sauropods like Diplodocus, which was inspired by fossil evidence of dung beetle activity in dung of ornithopod dinosaurs from the end of the Cretaceous (Maiasaura), rather than Jurassic sauropods. Phylogenetic studies in the 2010s indicate that dung beetles first diversified in the Early Cretaceous in conjunction with flower plants and ornithopod dinosaurs - thus supporting the paleontological consensus of The '90s, but going against the assumption of the show. Something must have eaten sauropod dung back then, but it wasn't our dung beetles.
  • The idea that sauropods relied on gastroliths to digest plant matter is also considered unlikely nowadays, since it would require hundreds of pounds of rocks to adequately grind up plant matter inside them, but gastrolith fossils are comparatively rare, strongly suggesting that sauropods did not have hundreds of pounds of rocks inside them all the time. More likely, sauropods just relied on their massive gut to slowly digest vegetation and simply happened to swallow rocks by accident on occasion while grazing.
  • The shape of Diplodocus's head changed more dramatically as it grew, from a narrower and more triangular shape in subadults to the flatter muzzles of the adults.
  • Recent discoveries of well-preserved sauropod skulls show that they had gums covering their teeth and a keratin covering on the end of the mouth forming into a beak-like structure. This is in stark contrast to the series depiction of sauropods with fleshy lips or exposed teeth.
  • A well-preserved fossil of Stegosaurus found in 2019 shows that the animal was much more slender and long, as opposed to the more compact, hunchbacked reconstruction of the show.
  • In 2007, Othnielia has been established to be synonymous with the newly-coined genus Othnielosaurus according to studies on the teeth of Morrison ornithischians. And then in 2018, Othnielosaurus along with Drinker have been discovered to be the same animal as Nanosaurus.

Cruel Sea

  • Biomechanical studies have shown that skim feeding (as Rhamphorhynchus is shown doing) was not possible in known pterosaurs. Rhamphorhynchus itself is more likely to have hunted fish while swimming and diving.
  • Plesiosaurs gave birth to alive newborns in water just like the fish-like ichthyosaurs; and they perhaps could not crawl onto land because the shape of their chest.
  • Rhamphorhynchus has since been found to likely have been nocturnal while the closely related Scaphognathus was active in the same area during the day (an example of niche partitioning).
  • Evidence of pliosaurs as large as the one in the episode has now been discredited. The largest known pliosaurs were probably "only" around 15 metres or so at the most, and even that's pushing it. The fragmentary remains initially identified as that of Liopleurodon are now regarded as an unknown and yet unnamed genus. Liopleurodon itself was only about 21 feet long. Additionally, it should have a fluke on its tail, as should the Cryptoclidus.
  • It's now considered more likely that plesiosaurs such as Cryptoclidus swallowed stones to help grind up food items rather than for use as ballast; in some cases, the stones made up less than one percent of the overall predicted body weight of the animal, and so would have been of very little use to weigh the animal down.
  • Ophthalmosaurus could actually give birth to more than five pups at a time; apparently at least eleven.

Giant of the Skies

  • The Tapejara species featured has now been reassigned to Tupandactylus. We also now know that the head is too small and the males had a flat crest rather than a ridged crest.
  • The giant Ornithocheirus was based on a specimen now assigned to Tropeognathus. Though it was indeed very large for an ornithocheirid, the show chose high-end, improbable estimates for its stated size. In reality, the specimen probably had around an 8m wingspan. Additionally, the claim that Ornithocheirus would have to keep itself dry at all times in order to fly has also been proven wrong, as there is now substantial evidence to suggest that ornithocheirid pterosaurs were actually quite good at swimming.
  • The "American Iguanodon" from the fourth episode would probably be placed in the genus Dakotadon today.
    • It's doubtful the European Iguanodon was actually Iguanodon and not, for example, Mantellisaurus, Hypselospinus or Barilium.
  • Most enantiornithines are now known to have lacked tail fans, contrary to the Iberomesornis shown in the series. Some enantiornithes also seem to have two long feathers at the end of the tail, which the birds in the show lack. Known enantiornithines nests show that they also nested on the ground.
  • A recent study suggests that most Mesozoic birds probably incubated their eggs by burying them like modern crocodilians or megapodes, rather than sitting on them (however, as portrayed in the show, at least some enantiornitheans did nest in colonies, so they got that right at least).
  • Recent studies have shown Utahraptor was a more bizarre dromaeosaurid instead of the giant version of Deinonychus that was portrayed in the episode. For starters, it had a bulky body with relatively short hindlegs and tail, making it the raptor version of a saber-toothed cat, and its jaw had a procumbent shape similar to Masiakasaurus.

Spirits of the Ice Forest

  • Some argue that Leaellynasaura needs plumage. It also might have actually had a really long tail, although it's not clear if these long-tailed fossils belonged to Leaellynasaura or a different, but similar animal.
    • Interestingly, the tails lack ossified tendons. This may have allowed the dinosaurs (whoever they were), to roll the tail over their bodies during their sleep, like foxes do today.
  • More recently, it's been suggested that the supposed large eyes of Leaellynasaura were actually just because it was a juvenile specimen rather than an adaptation for low-light conditions.
  • Remains of simple burrows have been found in the area since then, suggesting that Leaellynasaura sought refuge underground to survive the cold, rather than making nests above ground. Similar structures have been attributed to other small ornithopods in Asia and North America.
  • The "dwarf allosaur" seen in this episode was inspired by a single ankle bone found in the 1980s, which was tentatively attributed to Allosaurus for lack of a better genus to place it in. The researchers were not particularly convinced themselves that it was Allosaurus, what with being smaller, from the early Cretaceous rather than the late Jurassic and from Australia rather than North America; let alone, that it was an exact scaled-down replica of the North American dinosaur as the show portrayed it. An Australian theropod dinosaur that matches the ankle bone in size and age, Australovenator, was described in 2009. It also had longer arms than Allosaurus, with devastating claws.
    • If the "dwarf allosaur" was indeed Australovenator then it may not be an allosaurid at all, as some evidence suggests megaraptorans (the group of which Australovenator belongs to) are coelurosaurs, which also include tyrannosaurs.
  • Much like moas, wetas are now believed to have flown into New Zealand long after it separated from Australia and Antarctica, rather than being isolated there from the beginning.

Death of a Dynasty

  • The evidence for female Tyrannosaurus being larger than males is inconclusive at best, although considering that this pattern of dimorphism is seen in most large carnivorous birds as well as the most primitive birds today, it isn't improbable, there's just no direct evidence of it.
  • Recent papers suggest, contrary to most theropods, that most of Tyranosaurus was covered in scales (small amounts of feathers are still a possibility), however, the scales themselves were tiny, more akin to those seen of a bird's foot than the thicker, lizard-style scales seen in the show. In reality, the scales would have been too small to see unless you were standing very close. The snout is also believed to have had thick keratinous scales on it, too, which are absent in WWD's depiction.
  • The giant pterosaur Quetzalcoatlus is shown as a fish eater hunting prey on the wing, while we now know it was actually stork like in habits. In fact, it probably wouldn't have hesitated to eat juvenile tyrannosaurs, like the ones in the program! We now know Quetzalcoatlus actually had a much larger head and neck.
    • Additionally, pterosaurs were probably not "on the decline" at the end of the Cretaceous. Indeed, azhdarchids like Quetzalcoatlus were among the most successful animals at the time. In March of 2018, the notion that only azhdarchids were left at the time was completely decimated, as several genera of pteranodontid and nyctosaurid pterosaurs were discovered in Morocco strata that were dated to 67 million years. Additionally, not all Maastrichtian pterosaurs (even azhdarchids) were giants.
  • The body shape of the Quetzalcoatlus is more akin to the old reconstructions of the species with a short neck, sprawled posture, and Pteranodon-like crest, very different from the modern view, with a much flatter and frontal crest, erect stance, and massive head mounted on a long neck.
  • It's been theorized that Triceratops and Torosaurus (which were featured in Death of a Dynasty as seperate genera) are actually the same animal in different growth stages. However, research on this is still ongoing and has been doubted by some recent studies.
  • The accompanying book briefly mentions the possibility that Anatotitan is synonymous with Edmontosaurus. As of September 2011, this is the majority view. Also, in 2013 it was discovered that Edmontosaurus regalis had a crest of skin on its head, suggesting that E. annectens (the species that includes "Anatotitan") may have as well.
  • Anatotitan is portrayed with a flat, ducklike mouth, though we now know that Edmontosaurus had a flat beak that sat at a 90 degree angle from its mouth, much like the one Muttaburasaurs was given the previous episode.
  • At the time the show came out, Didelphodon was mostly known from teeth, which were exceptionally large and robust for a Cretaceous mammal. A skeleton was later found, revealing that it was shorter-legged, leaner, and semiaquatic, like an otter. The robust teeth were probably to crush freshwater crabs and molluscs. This is ironic, because Didelphodon is used in the show as an argument for dinosaurs "oppressing" mammals and keeping them from diversifying during the Mesozoic, but in reality it was an example of higher mammalian diversity in the Mesozoic than commonly assumed.
  • The generic raptor is simply identified as a "dromaeosaur", because at the time, there wasn't a named dromaeosaur species that was known to have existed alongside Tyrannosaurus; now there are known to be at least three (Dakotaraptor, Acheroraptor, and Dineobellator, with the last one being from New Mexico).
  • Ankylosaurus is now considered to be shorter in height and have a less arched, flatter back, meaning it would have aimed for the tyrannosaur's tibia rather than the femur. Its armor was also a lot more complicated than in the show.
  • The crew went to great pains to film on areas of Chile with no grass. In truth, its now known that grass was already present in the Late Cretaceous (whether it was present in large amounts in the Hell Creek region is still unclear however).
  • It has been now revealed that hadrosaurs had horse hoof-like forefeet, with a spiked index finger.
  • The episode sets the tone that even before the asteroid arrives, dinosaurs are already doing poorly due to increased global volcanism poisoning the environment with toxic fumes, and the meteor is more like the straw that broke the camel's back. However, this stance on dinosaur mass extinction is highly contentious, and many newer studies indicate evidence for a drop in end-Cretaceous dinosaur diversity brought on by mass volcanism is inconclusive at best. The prevailing view now is that an impact event was indeed the primary reason for their extinction and they were doing very well beforehand.

Walking With Beasts:

New Dawn

  • Debatable with the brief shot of a tamandua, likely meant to represent Eurotamandua from the Eocene of Messel, which was initially identified as an anteater. More recent studies indicate that it probably wasn't an anteater and quite likely it wasn't a xenarthran at all. However, the alternative is that it was a primitive, arboreal pangolin with no armor. This makes sense (since anteaters originated in South America while pangolins appeared in Eurasia, and other pangolins are known in Europe at this time) but also means that Eurotamandua, in the flesh, would look very much like a tamandua even if it wasn't a real tamandua. The use of a tamandua as a stand-in should be perfectly excusable. The use of a coati as a stand-in for the giant platypus Steropodon in WWD, on the other hand... not so much.
  • Whether the robust beak of Gastornis was to crush large nuts or small animals has been a matter of debate since its discovery. WWB went with the animals and presented Gastornis as the top predator in the Eocene European jungle. However, the latest study on calcium isotopes found that Gastornis' data was more similar to herbivorous mammals and reptiles (such as dinosaurs). There goes the show's iconic line about the Eocene being a time when birds ate horses.note  More likely creodonts (the order containing Hyaenodon), mesonychids, and terrestrial crocodilians such as Boverisuchus would have been the apex predators.
    • Eggshells from France reveal Gastornis eggs were similar in size to cassowary eggs, while the one in the episode seems ostrich-size if not larger. Cassowaries lay three eggs or more at once.
  • It's not completely agreed up whether leptictids hopped like modern kangaroos, or walked bipedally like theropod dinosaurs. A close relative of Leptictidium, Leptictis is currently believed to have walked rather than hopped, but differences between the skeletons make it insufficient evidence to suggest either way for Leptictidium.
  • Ambulocetus most likely couldn't support itself on land, and was fully aquatic despite still having limbs.

Whale Killer

  • Andrewsarchus, known only from a skull and a few fragments of bone, was assumed at the time the series was produced to be closely related to the mesonychids, and modelled after them. However, later phylogenetic studies indicate that it might have actually been a close relative of entelodonts and therefore might have been much less wolf-like than portrayed. Like entelodonts, it may have also been more omnivorous and not a pure carnivore.
    • And on that note, mesonychids most likely weren't the true ancestors of whales. Later studies have found whales to still be ungulates, but closer to the ancestors of hippopotamuses than more basal groups like the mesonychids (it helps that both hippos and whales are aquatic).
    • Ironically, these two corrections have coalesced into Andrewsarchus being still a land-dwelling relative of whales, but in a different branch of the ungulate family tree than previously assumed.
  • Basilosaurus was a shallow-water predator, while the show had it as being forced into shallow water from the open sea.
  • Apidium is now dated to the Oligocene instead of the late Eocene as portrayed in the show.
  • It's been suggested that the horn-like bony growths on the nose of brontotheres like Embolotherium were not free-standing, but actually the anchoring point of a large, fleshy nasal cavity that acted as a resonating chamber (similar to the crests of hadrosaurs). Not all brontotheres would've had this, as there were other species that did have them free-standing and used for interspecific combat and defense.

Land of Giants

  • Indricotheres were not completely invulnerable to predation, as bones from the Bugti beds in Pakistan have revealed tooth marks of bear-dogs and a 11-meter long crocodile, Astorgosuchus bugtiensis.
  • While paleontologists never expected Paraceratherium to behave like a carbon copy of African rhinos, this depiction became even less plausible after Prothero reviewed the group's biology extensively a decade later. One of the conclusions was that a mammal the size of Paraceratherium would be in permanent risk of overheating, so it would be mostly nocturnal or crepuscular, and spend the day in the shade, bathing, mud-bathing, or near water. Since indricotheres fed on tree leaves only, they would avoid depleting their food source by moving constantly from one forested area to another, which would not tire them due to their size, and might do yearly migrations like giraffes and elephants (but not modern rhinos). This would be specially true in desertic areas like the one shown in the episode. Ranging areas would be enormous and densities very low; to guarantee that mating happened at replaceable rates, the females may live in herds or family groups.
    • Isotope data from central China is also consistent with indricotheres feeding mostly on riverine forests, even when the territory around was desert-like.
  • There is some anatomical evidence to suggest indricotheres may have had a small trunk like a tapir instead of the pointed rhino-like fleshy lip the show used (although the latter is still plausible).
  • Male indricotheres were found to have longer tusks than females, which at least strongly suggests that tusks were used in threatening or mating displays. This is not the case in the show where the threatening display is a combination of African rhinos and giraffes.
  • Andrews originally restored "Baluchitherium" as a tremendously massive animal even by rhino standards, most likely as a way to make sure that "he" had found the largest land mammal of all time. The reconstructions lost weight through the 20th century, and this process continued after the show. Nowadays, some no longer believe it was the largest land mammal of all time but was surpassed by the elephant Palaeoloxodon namadicus, although it is still the tallest (and the line about being the largest land animal since the dinosaurs is still true).
  • Geologists now place the end of the Oligocene at 23 million years ago, instead of 25.

Next of Kin

  • Dinofelis was not too slow to catch "fast prey" and did not rely exclusively on "slow prey" like Australopithecus. A 2002 study on calcium isotopes of fossil carnivores that lived alongside australopithecines found that Dinofelis likely primarily hunted large ungulates, with leopards and smaller sabre-toothed cats being the main primate-hunters. However, modern big cats generally tend to specialise in whatever prey is readily available and, sometimes, what prey their mother taught them to hunt. So, even if Dinofelis itself was not a specialist primate-hunter, individual Dinofelis probably were.
  • The Deinotherium model follows the theory that deinotheres had shorter trunks than elephants. This was based on the facts that deinotheres separated early from the proboscidean family tree, and that their skulls lack the attachment marks corresponding to some trunk muscles, which were interpreted as deinotheres lacking these muscles, and as a result having shorter and more primitive trunks than elephants. It was later found that elephants don't have these marks either, because the muscles actually attach to other muscles in the trunk rather than the skull. If deinotheres didn't have them, it could be because they had long, advanced, elephant-like trunks, rather than the opposite. Finally, the authors of the later study appealed to common sense: while deinothere necks are slightly longer than elephant's, their legs are also longer, and they are not better at kneeling than elephant legs are. This means that if deinotheres had trunks as short as depicted in the show, the animals would be nearly incapable of drinking without getting partially submerged in water. However, some paleontologists believe deinotheres still wouldn't have long trunks since they diverged from other proboscideans, and propose that their method of drinking was by submerging in water similar to how modern moose drink. The debate is still going on, but it's most likely deinotheres would have had longer trunks than in the show.
  • Musth likely has nothing to do with mating, but with helping elephants fight each other in times of scarcity.
  • There is increasing evidence that Australopithecus is not an ancestor of Homo at all, but a more vegetarian offshoot from a common ancestor, that eventually led to the specialist vegetarian genus Paranthropus. The last common ancestor of Australopithecus and Homo might be Ardipithecus (named from fragmentary remains in 1995; a much more complete specimen, called "Ardi", was unveiled in 2009) or an even earlier genus like Sahelanthropus or Orrorin. At any rate, the adaptation to bipedalism must have appeared already in the primitive East African jungle and was unrelated to its clearing and transformation into savanna. "Next of Kin" (as in Next to our Kin) still makes for a great description of Australopithecus, though.
  • Ancylotherium is no longer the last surviving chalicothere: Nestoritherium survived in SE Asia for a million years after Ancylotherium went extinct in Africa, contemporaneous with Homo erectus.

Sabre Tooth

  • Smilodon was a terrible runner and would not be able to chase prey in the manner shown, or even at all, due to its short tail making it harder for it to turn during a chase, and its more muscular body making it less suited for running chase than lions and tigers. It is now believed Smilodon was more strictly an ambush predator, like those cats, but instead of sprinting a distance, it used its muscular limbs to pin prey down before stabbing with its long canine teeth.
  • If Smilodon lived in packs, they would likely not have a lion-like structure (1-2 or so males with a lot of females), due to males and females being similar sizes. Wolf-like packs have been suggested (1 main male/female pair, with a mixed group of other members), although the evidence for any sort of pack is thin.
  • The species of Smilodon shown (S. populator) in the episode had not evolved yet when the show was set.
  • At the time the episode was produced, scientists believed that sabertooths had displaced terror birds as apex predators with their arrival, hence their depiction as scavengers. However, it is now considered more likely that the terror birds were still able to remain as apex predators in competition with the sabertooths. Also, the species would have been Titanis in reality, but a theory presented at the time was that Titanis was a synonym of Phorusrhacos, which is mentioned in some supplementary material. Eventually it turned out that not many large terror birds were still around in South America by the time Smilodon arrived in the continent, as Titanis is more well known from being the sole North American terror bird, and would've instead coexisted with the older Smilodon gracilis, the earliest known Smilodon.
  • The purported bones of Titanis dating back to about 10,000 years were incorrectly dated. There is no conclusive evidence of Titanis or any other (large) terror bird existing after 1.8 million years ago, for the final terror bird, Psilopterus, was a small genus going as far back as the Oligocene and outlasting every large terror bird that evolved since, before finally succumbing to extinction 100,000 years ago.
  • Narrowly avoided example with the Titanis-inspired functional wing claws, which made to the promotional images and accompanying books, but were cut from the show in the last minute. The existence of wing claws in Titanis was debunked about 4 years after the show came out. It was discovered that a type of wing articulation in Titanis, which had been earlier taken as indirect evidence of a claw, was also present in the closest living relatives of the terror birds, the seriemas. Yet seriemas don't have such claws in their wings.
  • Although it was suggested at the time by some that Megatherium and other giant ground sloths may have occasionally hunted or scavenged, this idea was always a fringe one due to the lack of evidence (and extensive counter-evidence, such as the lack of carnassials in ground sloths and the fact that no animal remain has been ever found in ground sloth dung - a very abundant fossil, by the way).
  • After a century and a half of mystery, DNA finally revealed Macrauchenia were very distant relatives of perissodactyls and true ungulates as a result.
  • Megatherium probably wasn't as hairy as commonly portrayed, due to its large size and the fact that it lived in a warm climate. If it was shaggy as in the show, it would have overheated.

Mammoth Journey

  • Ancient DNA studies have found that Europeans retained dark skin tones until the arrival of paler people from the Middle East and Siberia about 7,000 years ago. This means the episode's Homo sapiens should be of noticeable darker complexion than the neanderthals, some of whom were red haired.
  • The interpretation of the Jersey cliffs as killing sites where neanderthals drove mammoths over the edge and butchered them below has been questioned. The mammoth bones might have just rolled downhill and accumulated there naturally, long after their owners died. However, due to the presence of tool marks in the bones, it is still possible that the mammoths were killed by neanderthals in some other way.
  • Nowadays it's known that neanderthals were not shorter than H. sapiens, and were more or less the same average height.
  • The 2016 discovery of two frozen cave lion cubs in Siberia with the same sandy color as modern African lions has cast further doubt on the theory that cave lions were white haired or turned white haired in the winter. This idea always had a lot of Rule of Cool involved, as well.

Walking With Cavemen:

Blood Brothers

  • H. habilis status as a human ancestor is slowly eroding with each new discovery. It is possible toolmaking was more widespread than previously believed, and that Homo ergaster type hominids evolved earlier than previously thought and thus not from H. habilis.
  • It's been suggested that there was just one Homo species in this time, that was a very plastic one (think dogs rather than people) and as a result, H. rudolfensis and H. habilis were the same species (maybe even H. ergaster, as well - but this is extremely far from the consensus).

The Survivors

  • It's been argued that the H. heidelbergensis of the Pit of Bones are not actually H. heidelbergensis, but early Neanderthals. If true, H. heidelbergensis should probably be considered as existing before 500,000 years ago only (the approximate age of the Pit of Bones remains).
  • The "H. heidelbergensis not caring for their dead" bit was taken from H. georgicus: The type locality of this species was interpreted later as a sabertooth cat den. Maybe they could not bury these dead because they were hunted by cats and unretrievable. Or maybe they really didn't care about their dead.

Walking With Monsters:

  • The Giant Spider in the Carboniferous was based on Megarachne, which ultimately turned out to be eurypterid ("sea scorpion") rather than spider. This was actually an error found out during production, but at that point it was too late to change the model (since the story hinged on Megarachne being a spider), so they just avoided naming the specific animal, opting instead to calling it a generic "Mesothelae", a basal suborder of spiders that evolved in the Carboniferous and survives today with only one extant family, the liphistiids.
  • Arthropleura is now considered to be a true millipede rather than simply a distant relative of the group.
  • There is increasing evidence to suggest that while increased oxygen in the air may have been a factor, giant land arthropods were able to exist primarily, or at least heavily, due to lack of competition from tetrapods, which were still just beginning to free themselves from the water. The giant land arthropods such as Arthropleura declined and became extinct the moment the land-dwelling reptiles started to produce large-bodied forms and provide serious competition. Giant flying insects continued to exist into the Permian and Triassic periods, and perhaps not coincidentally, became extinct just as the first flying vertebrates appeared (the pterosaurs).
  • The lineage that gave rise to mammals split to the one that gave rise to reptiles and birds before those developed the reptilian scales. The show represents perhaps the first time that Dimetrodon and its herbivorous "twin" Edaphosaurus have skins similar that of modern hairless mammals, instead of the classic scaly one. However, some think now that they would have the skin texture of a salamander, and the belly of a fish.
    • Surprisingly, Dimetrodon may have been nocturnal.
    • A study in 2012 suggested that in at least some Dimetrodon species, the sail may not have extended all the way to the very tips.note 
    • Interesting to note that the giant, Angry Guard Dog-looking Gorgonopsid from the show has scent glands (a typical mammalian feature).
  • The armoured plant-eating near-reptile Scutosaurus probably wasn't the ancestor of turtles. Recent research suggests that the latter were closer to modern reptiles than to Scutosaurus.
  • Euparkeria wasn't anything close to the "dinosaur ancestor" that the program makes it out to be. Not only did it evolve its bipedal gait independently from dinosaurs, it was more related to basal archosaurs, a group containing multiple major groups of reptiles other than dinosaurs. It was equally as related to crocodiles and pterosaurs as it was to dinosaurs.

Chased by Dinosaurs:

Land of Giants

  • This special portrayed the largest land animal of all time, Argentinosaurus, being hunted by the largest land predator, Giganotosaurus. Both have been supplanted since then: New evidence found that Spinosaurus was the biggest land predator (though it was partially aquatic), while Argentinosaurus has been surpassed slightly in length by 2006-described Turiasaurus (Argentinosaurus is still heavier, though).note 
  • Subsequent stratigraphic studies have shown that Giganotosaurus did not live at quite the same time as Argentinosaurus, although a close relative, Mapusaurus, did. That said, they did still live close enough together in time that some overlap could still be possible.
    • There is also no evidence that Giganotosaurus hunted in packs, although there is some indication that Mapusaurus did.
  • Argentinosaurus would have looked different than the Saltasaurus-like design in the show; giant titanosaurs are now known to have longer necks and upright-slanted postures similar to Brachiosaurus.
  • A biomechanical study cast doubt on the ability of Sarcosuchus to roll over like modern crocodiles. Though the authors are cautious in this regard, the implication is that Sarcosuchus was a strict fish eater and did not attack drinking animals on the shore, like modern gharials (similarly long snouted). Deinosuchus, seen in WWD and Prehistoric Park, did not have such problems.
  • The South American Iguanodon is now named Macrogryphosaurus, which, similar to Giganotosaurus, did not live at the same time as Argentinosaurus.
  • Later studies suggest that Pteranodon caught fish by diving into the water and swimming for their prey rather than snatching it up on the fly.

The Giant Claw

  • Feather issues aside, Velociraptor was likely nocturnal.
  • No trace of Therizinosaurus skin has been found, but the fact that its human-sized relative Beipiaosaurus had a complex feather cover makes it likely that Therizinosaurus had one too. The result looks like a cross between a goose and a ground sloth, much different from the show's naked model.

Sea Monsters:

  • The enormously long-necked Tanystropheus was portrayed as capable of losing and regenerating its tail like a lizard. In the past it was indeed suggested by palaeontologist Rupert Wildnote  that this creature was capable of autotomy, but other scientists who studied its fossils didn't find evidence for that. It has also been portrayed as an accomplished swimmer, but we don't know for sure if it really was such - its body-shape was all but hydrodynamic, and some think Tanystropheus was a shore animal who used its neck as a fishing rod, catching small prey a bit like a heron. Interestingly, the very similar Dinocephalosaurus, which probably was a true swimmer, was discovered the same year the special premiered.
  • In the accompanying book there is a Deleted Scene where female nothosaurs (primitive Triassic sea reptiles related to the more famous plesiosaurs) leave their eggs on the beach at night (see What Could Have Been on the Trivia page). However it turns out that nothosaurs might have been viviparous.
  • The show was made in 2003, and as a result missed out on the discovery of Livyatan melvillei. Its fossil was discovered in the same area as the C. megalodon episode, and had they set it just a bit earlier, both of these "monsters" would have appeared. Also of note is the fact that period had even more large marine carnivores than the Cretaceous.
  • A number of mosasaur fossils have been found with shark like tail impressions (one long fin, one short fin). These fossils, and various other arguments, suggest that most or all mosasaurs would have looked more fishlike than the ones shown on the show. This, combined with the fact that it was warm-blooded, would have made it an even faster, more active hunter and give it access to polar regions.
  • The largest mosasaurs probably didn't get as large in reality as they were portrayed because of this, as they would have had a more compact body shape. Lengths of between forty and fifty feet are considered more likely for the largest mosasaurs such as Mosasaurus or Tylosaurus.
  • Leedsichthys would have had a more smooth head than its bone-plated portrayal in the show. Also, careful examination of its size range puts it at around 16 meters and 40 tons as opposed to 30 meters and 150 tons.
  • Arsinoitherium, a relative of elephants that convergently resembled a rhinoceros, was probably more terrestrial than shown. It was published that it lived in rainforests inland and actually survived there for longer. So it lived in mangroves, but it wasn't a mangrove specialist as implied in the show.
  • In 2012, a much larger and better-armed relative of Cymbospondylus, Thalattoarchon (Or "Ruler of the Seas"), specialized in killing big sharks and other marine reptiles, dethroned it as the ultimate Triassic badass.

The Complete Guide to Prehistoric Life:

  • Othnielia and Leaellynasaura do not appear to be ornithopods, but more primitive ornithischians.
  • Page 122 claims that therizinosaurs are known from "a lone species" from North America, probably referring to Nothronychus. Enter the ancestral therizinosaur Falcarius in 2005...
  • To quote page 125, "Scientists cannot agree on whether Mononykus was a bird or a [non-bird] dinosaur." The 2010 discovery of the ancestral alvarezsaur Haplocheirus confirms that Mononykus and other alvarezsaurs were not birds.
  • There actually isn't any evidence that terror birds like the Phorusrhacos in the program had meathook claws on their wings. That idea came from an observation that one species, Titanis, had a very rigid wrist, suggesting the presence of some kind of digit. In 2005 it was pointed out that the birds' closest living relatives, seriemas, have the very same wrist, but no claws of any kind. However, seriemas do have a dromaosaur-like "sickle claw" on their second toe, suggesting that terror birds may have had that instead. It should also be noted that most birds do have some kind of claw or spur hidden under their wing feathers, but nothing like the flexing, slashing finger shown in the book's restoration. As mentioned above, the actual models in the show based on said concept art averted this by removing the claw.
  • Entelodon was not as closely related to pigs as was believed. It is now thought to be closer to whales and hippos, though as pigs were artiodactyls as well, it makes them a bit close, but still distant.

Walking with Dinosaurs 3D:

  • Just after they finished the Gorgosaurus models, Yutyrannus (a feathered tyrannosaur) was found, although the possibility of tyrannosaurids proper being unfeathered was revived in 2017, especially since Yutyrannus came from a more primitive side branch to later tyrannosaurs.
  • Mere days before the movie premiered, it was discovered that Edmontosaurus had a small fleshy crest on its head. Or at least one species, E. regalis, did (this is the species most likely depicted in the film, as the other Edmontosaurus species, E. annectens, is only known from fossil formations much younger than than the other dinosaur species in the movie).
  • A 2016 study suggested that the Alaskan Edmontosaurus may be its own genus, Ugrunaaluk; although a subsequent study in 2017 disputed this.
  • A study in 2017 has established Troodon to be a dubious taxon due to being only known from a tooth, a similar case with such dubious taxa as Trachodon or Monoclonius. The same study also re-established Stenonychosaurus as a valid genus again, due to being known from better remains (which were formerly assigned to Troodon). The Troodon in the film would have been better termed as Stenonychosaurus instead.
  • More recent studies have indicated that the Alaskan dinosaurs (including Pachyrhinosaurus and Edmontosaurus/Ugrunaaluk) were probably present in the region year-round and did not migrate.


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