History ScienceMarchesOn / WalkingWith

* 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).

* The opening for the episode states the indricothere as being the largest land mammal of all time, but [[https://www.app.pan.pl/article/item/app001362014.html a study in 2015]] found that the extinct elephant species ''Palaeoloxodon namadicus'' may have gotten bigger by about five tonnes (17 tonnes for ''Paraceratherium'' vs 22 tonnes for ''Paleoloxodon''). However, the study based this on two partial bones discovered and measured in the early 19th century, not from direct examination of these fossils, so it still requires further confirmation. Also the study found the largest ''Paraceratherium'' could have reached 17 tonnes rather than 15 as stated in the episode.

* ''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 weight measurement given in the episode is also a bit higher than the maximum weight estimates considered plausible nowadays (over 70 tonnes versus less than 60 tonnes). This is likely due to weight calculation methods done on ''Giraffatitan'' (then considered a species a ''Brachiosaurus'', as noted in the companion book, which includes Africa as part of '''Brachiosaurus''' range) which are now considered to be flawed.

* Another error with the ''Placerias'' is depicting them with tusks. Unlike most dicynodonts, ''Placerias'' actually had horn-like protrusions of bone projecting straight from its skull rather than tusks (technically, it also had tusks, but they're very small and hidden underneath these protrusions).
* Another minor error is that ''Placerias'' is known from two morphotypes of equal ratio, one with longer tusks than the other, and usually believed to be the male and female forms (this was actually noted in scientific descriptions long before the production of [=WWD=], but the literature was rather obscure and would've been difficult to find, making this a borderline example), but the version here is depicted without this dimorphism.
* The most glaring example by far is how ''Postosuchus'' and ''Placerias'' are both depicted as sluggish and ungainly relics from a bygone age that are destined to be supplanted by the “superior” dinosaurs (not unlike how we used to view [[DumbDinos dinosaurs]] themselves back in the early to mid-20th century in relation to mammals), who are framed as being more versatile, fleet-footed and have the unique gift of bipedalism. Suffice to say, none of that is true, as all terrestrial Triassic tetrapods were just as agile, sophisticated, and well-adapted to their enviroment as early dinosaurs and most of them likely died out as a result of the [[https://en.wikipedia.org/wiki/Triassic%E2%80%93Jurassic_extinction_event Triassic-Jurassic mass extinction]], which also allowed dinosaurs to take over ([[HistoryRepeats in the same way mammals took over thanks to the K-T mass extinction]])[[note]]The narration by Creator/KennethBranagh does mention the Triassic-Jurassic extinction during the credits, mostly glossing over it by stating how the dinosaurs have continued to evolve[[/note]], and bipedalism wasn’t unique to dinosaurs, as several other contemporary archosaurs, such as rauisuchids (including ''Postosuchus''), proposaurids, and shuvosaurids were also bipedal and shared many other morphological similarities to true dinosaurs (the last of which looked [[https://en.wikipedia.org/wiki/Effigia#/media/File:Effigia_BW.jpg nigh-identical to dinosaur]] [[https://en.wikipedia.org/wiki/Shuvosaurus#/media/File:Shuvosaurus_BW.jpg to the untrained eye]]).

* The episode also depicts the European ''Anurognathus'' in North America and interacting with otherwise North American animals. This is probably because the actual pterosaur fossils of the Morrison Formation are pretty terrible. However, the genus ''Mesadactylus'' was tentatively classified as an anurognathid in 2007, so they could have used that instead of ''Anurognathus'' nowadays.
* The WWD portrayal also places ''Anurognathus''' eyes in the wrong skull hole, the upper temporal fenestra rather than the orbit, making its face seem longer than it really was. Notice the shrinkwrapped circle in front of the eye in [[https://i.imgur.com/w3VAzGd.jpg this prop]]? That's where the eye ''should'' be. This is what makes it likely that ''Anurognathus'' was actually a nocturnal predator; its eyes [[https://qilong.files.wordpress.com/2013/03/anurognathus-ammoni-eyeball.png were enormous]] (each eye ''alone'' was bigger than its brain). Where WWD placed its eyes were actually where jaw muscles would have been attached. However, at the time, ''Anurognathus'' was only known from very scrappy and crushed skull material, and it wasn't until 2007, when a well-preserved complete skeleton was found, that this mistake was rectified.

* The largest known pliosaurs were probably only around 12 metres or so at the most, and even that's pushing it. As detailed in the tie-in book ''Walking with Dinosaurs: The Evidence'', the whale-sized ''Liopleurodon'' was based on an [[http://markwitton-com.blogspot.com/2020/04/in-pursuit-of-giant-pliosaurids-and.html assortment of jaw and snout fragments from Oxford Clay, as well as one vertebra around 25 cm in width housed at the Peterborough Museum]] (the latter of which turned out to have come from a sauropod), which were interpreted at the time as stemming from pliosaurs reaching up to as 20 meters in length, with the main ''Liopleurodon'' of the episode being stated to be an [[BiggerIsBetter unusually large specimen]] of a species that ''on average'' reaches 18-20 meters in length. Further complicating things, some taxonomic shifting down the line transferred the largest alleged ''Liopleurodon'' remains (attributed to animals reaching 8-11 meters), such as the massive "Cumnor mandible", to the related ''Pliosaurus'', leaving ''Liopleurodon'' in the 5.5-7 meter range. Though it was still the biggest killer of its day before being replaced by (or possibly evolving into) the larger ''Pliosaurus''.

* Additionally, it should have a fluke on its tail, as should the ''Cryptoclidus''.

** Addtionally, the North American ''Polacanthus'' is now seen as a separate taxon, ''Hoplitosaurus''.
* The narrator also alludes to ''Iguanodon'' being a highly successful genus that was both widely distributed and lasted for tens of millions of years, but this was due to ''Iguanodon''’s former status as a [[https://en.wikipedia.org/wiki/Wastebasket_taxon wastebasket taxon]], when any mid to large-sized ornithopod fossils from the Early to Mid Cretaceous (even if they were very fragmentary) were lumped into it. Subsequent studies, however, found that the only fossils attributable to ''Iguanodon'' come from Western Europe (Great Britain, Belgium, Germany, and Iberia) during the Barremian and early Aptian (130-122 mya), and even then, many iguanodont fossils from the Early Cretaceous of Europe have been reassigned to different genera like ''Hypselospinus'', ''Barilium'', and the aforementioned ''Mantellisaurus''.

** 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 episode also states that ''Quetzalcoatlus'' had a wingspan of thirteen metres; this was actually conservative at the time, but nowadays, with better knowledge of azhdarchid anatomy, a maximum wingspan of about eleven metres is considered more likely.

* The episode also depicts ''Anatotitan/Edmontosaurus'' as being considerably smaller than ''Tyrannosaurus'', but newer fossils indicate it was actually much larger, with specimens such as MOR 1142 and MOR 1609 suggesting lengths of over fifteen metres and possibly up to fifteen tonnes for some adults, far out-weighing the biggest ''T. rex''.

** 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 [[RightForTheWrongReasons still a land-dwelling relative of whales]], but in a different branch of the ungulate family tree than previously assumed.

* 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.

** As mentioned before, ''Andrewsarchus'' is also classed as a member of Cetancodontamorpha, and is considered to possibly be a close relative of entelodonts, thus making it rather [[HilariousInHindsight humorous in hindsight]] how different the show’s models for these two ungulates are, as conventional wisdom nowadays is that ''Andrewsarchus'' paid a stronger resemblance to entelodonts (to what extent is unclear).

* Paleoartistic reconstruction have also increasingly moved from showing ''Macrauchenia'' with a long, almost comical trunk to a more boring moose-like snout, though there is still no conclusive evidence for either.

*** Additionally, the group includes "insectivores", "creodonts", and "lepticids", groups with have since been found to be wastebasket taxa, the latter two being probably paraphyletic. Lepticids are also shown as placental mammals, but some studies find them as non-placental eutherians.

* ''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 weight measurement given in the episode is also a bit higher than the maximum weight estimates considered plausible nowadays (over 70 tonnes versus less than 60 tonnes). This is likely due to weight calculation methods done on ''Giraffatitan'' (then considered a species a ''Brachiosaurus'') which are now considered to be flawed.

* Debatable with the brief shot of a tamandua, likely meant to represent ''[[UsefulNotes/PrehistoricLifeMammals Eurotamandua]]'' from the Eocene of [[http://en.wikipedia.org/wiki/Messel_pit Messel]], which was initially identified as an anteater. Studies from 2010 indicate that it probably wasn't an anteater [[http://scienceblogs.com/tetrapodzoology/2010/03/the_anteater_that_isnt.php 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 ''[[UsefulNotes/PrehistoricLifeMammals 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]]Near the end of their time in the early Pleistocene, the superficially similar terror birds, which ''were'' carnivores, did however eat horses, as possibly did the giant bathornithids of North America.[[/note]] In addition, the idea of ''Gastornis'' being carnivores was already suspect, since the beak lacked a hook and its feet lacked claws. More likely creodonts (the order containing ''Hyaenodon''), mesonychids, and terrestrial crocodilians such as ''Boverisuchus'' would have been the apex predators.

* The ''Plateosaurus'' entry states that prosauropods did not evolve into sauropods, but later studies have found the the traditional idea was correct that prosauropods really were the director ancestors of sauropods and the group is paraphyletic.

* The ''Protoceratops'' entry states that the origin of "ceratopsids" (probably meaning the broader group, ceratopsians) are mysterious, and they may have evolved from heterodontosaurids. Fossils of Jurassic ceratopsians are now known, making their early evolution much more well-known. Interestingly, their sister group, the pachycephalosaurs, which is still mysterious, have been suggested to have evolved from heterodontosaurids since then.

* The episode depicts numerous Mid Jurassic species near the end of the Late Jurassic in one of the series' most egregious examples of AnachronismStew. However, this may primarily stem from the fact that numerous Late Jurassic pliosaur species were lumped into ''Liopleurodon'' at the time, but have either been reclassified as ''Pliosaurus'' species or are now considered too fragmentary to be diagnostic to ''Liopleurodon'' (the genus' validity was also been called into question in 2022, since the holotype is a single indistinct tooth). It's possible the producers extrapolated ''Liopleurodon'''s range from the Mid Jurassic to the Late Jurassic to the other animals it coexisted with.

* The WWD portrayal also places ''Anurognathus''' eyes in the wrong skull hole, the upper temporal fenestra rather than the orbit, making its face seem longer than it really was. Notice the shrinkwrapped circle in front of the eye in [[https://i.imgur.com/w3VAzGd.jpg this prop]]? That's where the eye ''should'' be. This is what makes it likely that ''Anurognathus'' was actually a nocturnal predator; its eyes [[https://qilong.files.wordpress.com/2013/03/anurognathus-ammoni-eyeball.png were enormous]] (each eye ''alone'' was bigger than its brain). Where WWD placed its eyes were actually where jaw muscles would have been attached.

* 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.

* 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]]Near the end of their time in the early Pleistocene, the superficially similar terror birds, which ''were'' carnivores, did however eat horses.[[/note]] In addition, the idea of ''Gastornis'' being carnivores was already suspect, since the beak lacked a hook and its feet lacked claws. More likely creodonts (the order containing ''Hyaenodon''), mesonychids, and terrestrial crocodilians such as ''Boverisuchus'' would have been the apex predators.

* The reasons for ''Chalicotherium'' showing up in the Late Oligocene can be chalked up to it being used as a [[https://en.wikipedia.org/wiki/Wastebasket_taxon wastebasket taxon]] in the past. The genus is known from some very complete material but all of those stem from the Late Miocene-Mid Pliocene (10-3.5 mya), with the oldest known fossils of chalicotheriines (the knuckle-walkers) stemming from the Mid Miocene (16-14 mya), while the only chalicotheres confirmed to have lived around the end of the Oligocene being the more basal schizotheriines (non-knuckle walking chalicotheres such as ''Ancylotherium'' introduced later), like ''Borissiakia'' (the best fit for “Land of Giants"). Very fragmentary fossils from the Late Oligocene-Early Miocene of Eurasia were previously lumped into ''Chalicotherium'', but those have since been deemed schizotheriines or ''nomen dubia'', like “''Chalicotherium''” ''pilgrim'' (possibly a schizotheriine) and “''Chalicotherium''” ''wetzleri'' (now included in ''Metaschizotherium'', also a schizotheriine).

* The series uses the NoisyNature approach that was universal to dinosaur restorations at the time (although it's commendable here because the series went to the extra effort to give each animal species their own unique calls), such as giving sauropods whale-like bellows and ''Tyrannosaurus'' a MightyRoar, but later studies from [[https://www.tandfonline.com/doi/full/10.1080/08912960903033327 2009]] and [[https://www.semanticscholar.org/paper/Coos%2C-booms%2C-and-hoots%3A-The-evolution-of-vocal-in-Riede-Eliason/31e0da3514edeb7fe3c1dfb01c43d4545816c794 2016]] have suggested it's likely non-avian dinosaur vocalization would've been limited in comparison to modern birds and mammals due to crocodilians, as the closest relatives of dinosaurs, having a more primitive larynx compared to mammals, and the dinosaurs not having the syrinx that modern birds have for vocalization. Some of the predators, ''Postosuchus'' in particular, vocalize a lot while pouncing on their prey (though others, like ''Allosaurus'' and ''Utahraptor'', are more realistically silent).

* The evidence for female ''UsefulNotes/TyrannosaurusRex'' 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.

* The pliosaur which makes a very brief cameo is identified in supplementary material as ''Plesiopleurodon''. This specific genus was probably chosen because, at the time, it was considered a very close relative of ''Liopleurodon'' and looked very similar to it (hence the very similar names), so they could just use a very lazy PaletteSwap of their ''Liopleurodon'' to portray it (despite the massive AnachronismStew, due to the fact it lived during the Cenomanian, while the episode is set during the Barremian). However, it has since been reclassified as a polycotylid and therefore wasn't closely related to ''Liopleurodon''.[[note]]At the time of the show's production, all short-necked plesiosaurs were considered pliosaurs, but it has since been found that the short-necked condition evolved more than once amongst plesiosaurs.[[/note]]

* The pliosaur which makes a very brief cameo is identified in supplementary material as ''Plesiopleurodon''. This specific genus was probably chosen because, at the time, it was considered a very close relative of ''Liopleurodon'' and looked very similar to it (hence the very similar names), so they could just use a very lazy PaletteSwap of their ''Liopleurodon'' to portray it (despite the massive AnachronismStew, due to the fact it lived during the Late Cretaceous, while the episode is set during the Early Cretaceous). However, it has since been reclassified as a polycotylid and therefore wasn't closely related to ''Liopleurodon''.[[note]]At the time of the show's production, all short-necked plesiosaurs were considered pliosaurs, but it has since been found that the short-necked condition evolved more than once amongst plesiosaurs.[[/note]]

* The pterosaurs that are occasionally shown are identified by supplementary material as ''Azhdarcho'', the first azhdarchid ever described. But ''Azhdracho'' hails from the Turonian-aged Bissekty Formation (92-90 mya), and actually coexisted with much smaller forerunners of the giant dinosaurs found at Nemegt, such as ''Levnesovia'' and ''Timurlengia'' (a basal, small-bodied hadrosaur and tyrannosaur respectively). Its inclusion in the episode can, once more, be chalked up to wastebasket taxonomy, as workers once assigned many small-sized azhdarchid fossils from the Upper Cretaceous to the genus before we learned about the true diversity of the group. [[https://www.researchgate.net/publication/320219078_Gigantic_pterosaurian_remains_from_the_Upper_Cretaceous_of_Mongolia In 2017, the discovery of cervical vertebrae revealed the presence of a very large azhdarchid at Nemegt]], similar to ''Hatzegopteryx'', though smaller ones were likely present as well, since both large and small taxa are known to have coexisted in Europe and North America during the Late Cretaceous.

* ''Ornithocheirus'' is depicted in the episode making vast cross-continental migrations from South America to Europe due to the fact it was once thought to have lived on both continents; however, since the South American ''Ornithocheirus'' species has since been reclassified as ''Tropeognathus'', this is now considered dubious.

* The end of the episode gives off the impression that sauropods globally declined at the end of the Jurassic, which was a common view at the time (possibly why none appear in subsequent episodes). However, about the time the show came out, there were many new fossil remains of Cretaceous sauropods being discovered in the southern hemisphere, particularly South America, showing that they only seemed to have declined in the northern continents (and even then persisted until the end of the Late Cretaceous there in species like ''Alamosaurus'' and ''Magyarosaurus''), but continued to flourish in the south in great numbers and diversity.

* The ''Anomalocaris'' doesn't have the segmented body and cephalic plate on its head it's now believed to have had; rather bizarrely, the show's portrayal seems to have a single, solid, unsegmented plate covering its entire body. The species of ''Anomalocaris'' which the show based its portrayal on (previously known as ''Anomalocaris saron'') is now known to have been a chimera of two different dinocaridid species and subsequently named ''Houcaris'' (the great appendages) and ''Innovatiocaris'' (for the rest of the body), and the former was part of a group of ''filter-feeding'' anomalocarids.

* The pterosaurs that are occasionally shown are identified by supplementary material as ''Azhdarcho'', the first azhdarchid ever described. But Azhdracho hails from the Turonian-aged Bissekty Formation (92-90 mya), and actually coexisted with much smaller forerunners of the giant dinosaurs found at Nemegt, such as ''Levnesovia'' and ''Timurlengia'' (a basal, small-bodied hadrosaur and tyrannosaur respectively). Its inclusion in the episode can, once more, be chalked up to wastebasket taxonomy, as workers once assigned many small-sized azhdarchid fossils from the Upper Cretaceous to the genus before we learned about the true diversity of the group. [[https://www.researchgate.net/publication/320219078_Gigantic_pterosaurian_remains_from_the_Upper_Cretaceous_of_Mongolia In 2017, the discovery of cervical vertebrae revealed the presence of a very large azhdarchid at Nemegt]], similar to ''Hatzegopteryx'', though smaller ones were likely present as well, since both large and small taxa are known to have coexisted in Europe and North America during the Late Cretaceous.

* When Nigel initially sees a young ''Argentinosaurus'', he says that it's unmistakable what species it is. This statement is probably because ''Argentinosaurus'' was, at the time, the only sauropod species conclusively identified from the Huincul Formation. Four other sauropod species have since been described, making the statement that it can't be mistaken for anything else shakier. He says the same thing for ''Giganotosaurus'', but two large carcharodontosaurids have been identified from the Huincul Formation.

* The South American ''Iguanodon'' is now named ''Macrogryphosaurus'', which, similar to ''Giganotosaurus'', did not live at the same time as ''Argentinosaurus''.

* 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 discovered later that it also lived in inland rainforests in Ethiopia and actually survived there for longer than in Egypt; ''Arsinoitherium'' lived in mangroves, but it wasn't a mangrove ''exclusive'' as implied by the show.
* In 2012, a stockier 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.
** Surpassed and then some in 2021, with the description of ''Cymbospondylus youngorum'' (the largest species of its genus), which is estimated to have reached a [[https://www.reddit.com/r/Naturewasmetal/comments/rn8fjn/cymbospondylus_the_earliest_truly_giant/ gargantuan 14-17 meters and had a skull 1.9 meters long!]]

* ''[[UsefulNotes/PrehistoricLifeHadrosaurPredecessors Othnielia]]'' and ''[[UsefulNotes/PrehistoricLifeHadrosaurPredecessors Leaellynasaura]]'' do not appear to be ornithopods, but more primitive ornithischians.

* 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 "[[https://upload.wikimedia.org/wikipedia/commons/5/51/Seriamanail_%28high_res%29.jpg sickle claw]]" on their second toe, suggesting that terror birds may have had that instead. It should also be noted that [[http://scienceblogs.com/tetrapodzoology/2010/06/30/clubs-spurs-spikes-and-claws/ 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.

* On a similar note, the idea that imagination is what distinguishes modern humans from our ancestors came from the fact that no signs of art from other humans species had been found. Since then, it's been found that Neanderthals not carved artful objects and decorated them with pigments.

* On a similar note, the idea that imagination is what distinguishes modern humans from our ancestors came from the fact that no signs of art from other humans species had been found. Since then, it's been found that Neanderthals not only carved artful objects, they decorated them with pigments and may have even developed language.

** 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 [[RightForTheWrongReasons still a land-dwelling relative of whales]], but in a different branch of the ungulate family tree than previously assumed.
* The holotype hails from the Irdin Manha Formation, which turned out to be Mid Eocene in age (44-40 mya), not Late Eocene (39-34 mya), meaning it would not have been a contemporary of ''Embolotherium''. The apex predators of Late Eocene Asia would have been hyaenodonts and entelodonts (like the ones seen in "Land of Giants").
* ''Apidium'' is now dated to the Oligocene instead of the late Eocene as portrayed in the show.

* The introductory opening of the episode states that there were two different types of humans alive at the time (Neanderthals and Cro-Magnon), but a third variety of ice age human was identified in 2010, known as Denisovans, which may have survived as late as 14,500 years ago. However, they are still very poorly understood and is not known to have existed in the region the episode is set.

* The opening for the episode states the indricothere as being the largest land mammal of all time, but [[https://www.app.pan.pl/article/item/app001362014.html a study in 2015]] found that the extinct elephant species ''Palaeoloxodon namadicus'' may have gotten bigger by about five tonnes (17 tonnes for ''Paraceratherium'' vs 22 tonnes for ''Paleoloxodon''). However, the study based this on two partial bones discovered and measured in the early 19th century, not from direct examination of these fossils, so it still requires further confirmation.

* ''Dunkleosteus''' tooth-like extensions of its armor were later discovered to have been actual teeth that merged together. It also would likely have had lips covering them.
* [[https://www.mdpi.com/1424-2818/15/3/318 A study]] presented at the 2022 SVP and published in early 2023 suggests that the traditional size estimates of ''Dunkleosteus'' and other large placoderms are inaccurate and greatly embellished. It found ''Dunkleosteus'' was probably much shorter and more compact than previously thought, only about four metres long and less than two tonnes in weight (making it about the size of an average great white, but much heavier) instead of the ten-metre long, five-ton monster presented in the episode.

* ''Dunkleosteus'' is shown with a long 8-metre body, but as of 2023 it is known to have [[https://www.mdpi.com/1424-2818/15/3/318 a shorter more compact body]] half that, just under the size of a great white shark. The original size estimates are the result of using the oarfish, which is long but not muscular, as a baseline for the animal's reconstructions.

* ''Dunkleosteus'' is shown with a long 8-metre body, but as of 2023 it is known to have [[https://www.mdpi.com/1424-2818/15/3/318 a shorter more compact body]] half that, just under the size of a Great White Sark.

* Musth likely has nothing to do with mating, but with helping elephants fight in times of scarcity (in fact, musth-striken males will kill females rather than try mating with them).

* ''Dunkleosteus'' is shown with a long body, but as of 2023 it is known to have [[https://www.mdpi.com/1424-2818/15/3/318 a shorter more compact body]], just under the size of a Great White Sark.

* The ''Anomalocaris'' doesn't have the segmented body and cephalic plate on its head it's now believed to have had; rather bizarrely, the show's portrayal seems to have a single, solid, unsegmented plate covering its entire body. The species of ''Anomalocaris'' which the show based its portrayal on (previously known as ''Anomalocaris saron'') is now known to have been a chimera of two different dinocaridid species and now named ''Houcaris'' (the great appendages) and ''Innovatiocaris'' (for the rest of the body), and the former was part of a group of ''filter-feeding'' anomalocarids.

* The series depicts its gorgonopsid as being hairless and the narration states that fur has not evolved yet, but fossils [[https://onlinelibrary.wiley.com/doi/10.1111/let.12156 described in 2015]] found in the Late Permian of Russia (the exact time and location the specific episode is set) found direct evidence of hair. Whether the hair came from a gorgonopsid is unknown, but it's clear some sort of therapsid at the same time already did have fur.