History ScienceMarchesOn / WalkingWith

* Subsequent revisions of ''Tyrannosaurus'' anatomy indicate it was far more rotund than often depicted and its chest would've been much closer to the ground (as seen in a [[https://preview.redd.it/7ztfy21eg2e51.jpg?auto=webp&s=8524a994b0120effe630ca95a3873061bdffb7af a more modern reconstruction]], compared to [=WWD's=] [[https://i.ytimg.com/vi/JYF24vDemEo/hqdefault.jpg version]]). ''Tyrannosaurus'' is stated as weighing up to five tonnes, but most modern weight estimates suggest higher boundaries around seven to nine tonnes.

* There were no [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles cynodonts]] of the size depicted in the program in the late Triassic[[note]]other than traversodonts. Given that some Mesozoic mammals reached similar sizes (such as the infamous ''Repenomamus''), cynodonts that big in that time period aren't strictly unlikely, but unknown from the area the episode took place[[/note]]. This is an example of ScienceMarchesOn rather than ArtisticLicensePaleontology 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 [[http://chinleana.blogspot.com/2009/09/enigmatic-triassic-taxa.html two teeth]] from [[http://en.wikipedia.org/wiki/Chinle_Formation Chinle Formation]][[note]]though these teeth were assumed to belong to [[http://en.wikipedia.org/wiki/Traversodontidae traversodont]] cynodonts, very different from ''Thrinaxodon'' that WWD-cynodonts were based on[[/note]]. However, [[https://www.researchgate.net/publication/228488767_Unusual_tetrapod_teeth_from_the_Upper_Triassic_Chinle_Formation_Arizona_USA 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).

* Most [[UsefulNotes/StockDinosaursTrueDinosaurs coelurosaurs]] certainly had feathers. The several [[UsefulNotes/StockDinosaursTrueDinosaurs dromaeosaurid species]] surely had them, but in the franchise they are all shown featherless: this, rather than ScienceMarchesOn, might be interpreted more as RuleOfCool, or rather, ArtisticLicensePaleontology, since feathered raptors would have appeared "too cute"? In RealLife dromeosaurids had WINGS just like their famous relative, the "ur-bird" ''[[UsefulNotes/StockDinosaursTrueDinosaurs 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 theory was led by the discoveries of the primitive herbivore ''[[UsefulNotes/PrehistoricLife Tianyulong]]'' in China and ''Kulindadromeus'' in Russia, and further supported by [[https://www.nature.com/articles/s41559-018-0728-7 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 [[http://en.wikipedia.org/wiki/Surface-area-to-volume_ratio#Biology surface area to volume ratio]]. Some think the "spikes" on ''[[UsefulNotes/StockDinosaursTrueDinosaurs Diplodocus]]'' have the same common origin of feathers, as well as the quill of the small herbivore ''[[UsefulNotes/PrehistoricLifeHadrosaurPredecessors Psittacosaurus]]'' and even the horny bumps lined on the back of several [[UsefulNotes/StockDinosaursTrueDinosaurs hadrosaur mummies]].

* ''Tropeognathus'' and ''Tupandactylus'', known from the Brazilian Santana Group, specifically the Romualdo and underlying Crato Formation respectively, are shown living 127 million years ago (middle Barremian), but the ages of Romualdo and Crato have subsequently been reinterpreted as early Albian (112-108 mya) and late Aptian (115-113 mya) respectively. The same AnachronismStew is present with the sympatric ''Anhanguera'' in ''Series/DinosaurRevolution''.

* The episode depicts female ''Tyrannosaurus'' as being larger and more vicious than males, based on then supposed evidence of "gracile" and "robust" morphs of ''T. rex'' fossils and a supposed egg canal gap in the tail vertebrae known in the "robust" morphs, as known in modern crocodilians, so the "robust" morph was considered the female (the 'making of' program has them identifying the very large and extremely robust "Sue" ''Tyrannosaurus'' specimen as female). However, shortly after the series was broadcast evidence for female's being larger was severely weakened by the fact the supposed egg canal anatomy found in crocodilians was in error, so it could not be used to accurately determine dinosaur sexes, and the extremely robust "Sue" specimen had a fully intact tail vertebrae anyway, contradicting the idea regardless. 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.

* At the time the show came out, ''Didelphodon'' was mostly known from teeth, which were exceptionally large and robust for a Cretaceous mammal, leading to badger-like depictions, as in this episode. 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.
** Interestingly, there is another mammal that lived alongside T. rex, called ''Nanocuris'',which might fit the profile of the WWD ''Didelphodon'' a lot better, as it was a member of the [[https://www.deviantart.com/midiaou/art/FC-Deltatheridium-654910222 deltatheridiids]], who were likely active predators and might have even ''preyed on baby dinosaurs'', as the skull remains of a juvenile troodontid from Mongolia sport bite marks made by a deltatheridiid.

* ''Tapejara'' (now known as ''Tupandactylus'') is described as being a carnivorous fish eater. ''Tapejara'' is now speculated to have been a hornbill or toucan-like fruit-eater or omnivore, while ''Tupandactylus'' is thought to have been a ground-dwelling raptorial predator.

* The episode depicts numerous Mid Jurassic species near the end of the Late Jurassic in one of the series' most egregious examples of AnachronismStew. This likely stems from the fact that ''Liopleurodon'', ''Cryptoclidus'', and especially ''Ophthalmosaurus'' were used as wastebasket taxa in the past, with various pliosaurid, cryptoclidid and ichthyosaur fossils from the Late Jurassic being attributed to them respectively, and in the case of ''Ophthalmosaurus'', even some Early Cretaceous ichthyosaurs material, but those younger specimens have all since been placed in different genera, reclassified as new genera or have been deemed too fragmentary to be diagnostic, leaving the former three restricted to the Callovian-early Kimmeridgian (166-155 mya). There was, however, no excuse for ''Eustreptospondylus'', who is only known from its Oxfordian-aged holotype (circa 160 mya).

* 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 direct ancestors of sauropods and the group is paraphyletic.

* While all of them stem from the Late Cretaceous Nemegt Basin group, the cast of the episode wouldn't have all been contemporaries in real life. ''Therizinosaurus'', ''Tarbosaurus'', ''Mononykus'', and ''Saurolophus'' all come from the Nemegt Formation, which overlies the Barun Goyot Formation, and it, in turn, overlies the Djadochta Formation (which houses ''Velociraptor'' and ''Protoceratops''). To complicate matters, a 2023 study using radiometric dating on ''Tarbosaurus'' teeth from Nemegt pushed up the age of the formation from 70-68 mya to the very end of the Maastrichtian, circa 68-66 mya, making its fauna contemporaries of T. rex and the other Hell Creek dinosaurs in North America, and quite a bit younger than ''Velociraptor'' and ''Protoceratops'' (who lived during the late Campanian, 75-72 mya). Nemegt did house a medium-sized dromaeosaur (and possible velociraptorine) called ''Adasaurus'', but no protoceratopsid fossils are known from the biome (their last known occurrence being at Barun Goyot).

* The cast of the episode wouldn't have all been contemporaries in real life. ''Therizinosaurus'', ''Tarbosaurus'', ''Mononykus'', and ''Saurolophus'' all come from the mid Maastrichtian Nemegt Formation (which gets namedropped by Nigel, meaning it's the episode's setting), which overlies the early Maastrichtian Barun Goyot Formation, and it, in turn, overlies the late Campanian Djadochta Formation (which houses ''Velociraptor'' and ''Protoceratops''). To complicate matters, velociraptorine and protoceratopsid fossils from the intermediary Barun Goyot Formation have subsequently been reassigned to separate genera (''Kuru'' and ''Shri'', and ''Bagaceratops'' respectively), which widened the age gap. Nemegt did house a medium-sized dromaeosaur (and possible velociraptorine) called ''Adasaurus'', but no protoceratopsid fossils are known from the site. Furthermore, Nemegt and Djadochta turned out to be quite different biomes, with the former being an alluvial plain and thriving with large dinosaurs, while the latter was more arid and desert-like (complete with sand dunes), and mainly housed small dinosaurs.

* The idea that the Hell Creek ecosystem was a barren wasteland with only patches of forest scattered across it is entirely incorrect, volcanism or not. We know from both the fossil flora and the abundance of small animals like mammals, birds, fish, turtles, and crocodiles that Hell Creek was a lush, alluvial flood plain environment much more akin to today’s Everglades, but with araucaria conifers and ferns in place of grass rather than the ash fields of Chile.

* The pterosaurs that are occasionally shown are identified by supplementary material as ''Azhdarcho'', the first azhdarchid ever described. But ''Azhdarcho'' 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.

** 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.

* ''Tapejara'' (now known as ''Tupandactylus'') is described as being a carnivorous fish eaters. ''Tapejara'' is now speculated to have been a hornbill or toucan-like fruit-eater or omnivore, while ''Tupandactylus'' is thought to have been a ground-dwelling raptorial predator.

* ''Ambulocetus'' most likely [[https://www.sciencedaily.com/releases/2016/07/160725105228.htm couldn't support itself on land]], and was fully aquatic despite still having limbs.

* Paleoartistic reconstruction have 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. However, prehistoric rock art discovered in the Amazon in 2020 depicting trunked, long-necked animals has brought the possibility of ''Macrauchenia'' possessing a proboscis into the fray again.

* The "American ''[[UsefulNotes/StockDinosaursTrueDinosaurs Iguanodon]]''" would probably be placed in the genus ''[[http://dx.doi.org/10.1016/j.cretres.2007.04.009 Dakotadon]]'' today.
* The North American ''Polacanthus'' is now seen as a separate taxon, ''Hoplitosaurus''. The line that ''Polacanthus'' are "often found around ''Iguanodon'' herds" probably also comes from the fact that it, just like ''Iguanodon'', was at the time a huge wastebasket taxon, with many different nodosaurid fossils from throughout the United Kingdom, Spain, and (in ''Hoplitosaurus''' case) North America attributed to it. However, a 2020 study found that only the holotype could be conclusively attributed to ''Polacanthus'', and all other European fossils were too scrappy to conclusively classify.
* The narrator 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''.

* The episode depicts plesiosaurs as having an alternating flipper stroke, but biomechanical tests done since has found this method of locomotion was pretty inefficient due to the vortexes created by the stroke of the front flippers resulting in significant turbulence that would hinder propulsion generated by the delayed stroke of the back flippers. A 2017 study with mechanical plesiosaur fins found that the most efficient gait for plesiosaurs was all four flippers moving almost in unison, with the back flippers stroking just after the front pair to ride in its immediate wake.

* The ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles 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 North American ''Polacanthus'' is now seen as a separate taxon, ''Hoplitosaurus''.

* Paleoartistic reconstruction have 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.

* The [[PteroSoarer giant pterosaur]] ''[[UsefulNotes/StockDinosaursNonDinosaurs Quetzalcoatlus]]'' is shown as a fish eater hunting prey on the wing (the episode implies that it's normally a seagoing animal and happened to come in from the coast, seemingly ignoring that its remains are known entirely from semi-arid inland ecosystems that would've been hundreds of kilometres from the sea), 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.

* ''Andrewsarchus'' is 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).

* Megalodon is identified as a ''Carcharodon'' species (the same genus that the modern great white belongs), but subsequent studies place it in the extinct genus ''Otodus''.

* ''Rhamphorhynchus''' specified range includes Tanzania, but these so-called remains, once dubbed "Rhamphorhynchus tendagurensis", has since been reevaluated as being too scrappy to concretely belong to the genus.

* ''Iguanodon'' is said to have inhabited Eurasia and North America 140-112 mya (Valanginian-early Albian), which was actually a more ''conservative'' description of its alleged temporal/geographic range compared to what some other sources claimed at the time. Still, besides the aforementioned American ''Dakotadon'', fossils from the Aptian-Albian of Central Asia previously attributed to ''Iguanodon'' have either been deemed ''nomen dubia'' or reassigned to ''Altirhinus'', while in Western Europe, the Valanginian species have been reclassified as ''Barilium'' and ''Hypselospinus'', leaving ''Iguanodon'' restricted to the Barremian-earliest Aptian.

* ''Ornithocheirus'' is said to have lasted pretty much the entirety of the Cretaceous (140-70 mya) and that it had an almost cosmopolitan distribution, both of which reflect its former status as a wastebasket taxon, with the type species, O. ''simus'', now being restricted to the Albian of Britain, while many other Mid Cretaceous species have been reassigned to various different genera. The very Early Cretaceous ones have been reclassified as ''Serrodraco'' and ''Targaryendraco'' respectively, and the claim that it lasted until the Late Cretaceous is based on the Campanian “''Ornithocheirus buenzeli''”, known only from a humerus and jaw fragment now thought to represent an azhdarchid.

* ''Placerias'':