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SETTING: Montana, Late Maastrichtian (66 MYA)

And here we move to the final episode of the original series (and a bit of a segue into the prologue of the sequel episode), where we return to North America for the fourth time, a few months before the fated asteroid is about to merge Heaven and Earth, bringing about the end of the age of reptiles. Despite what they may tell you, dinosaurs were continuing to flourish on every continent (well, we don't really know what was happening on Australia, but probably dinosaurs were still dominating there) in great diversity, size, and numbers. The episode presents an incredibly skewed and dubious view of Hell Creek, showing intense volcanism rendering much of the region an inhospitable wasteland (repeated in the Impossible Picture's spiritual follow-up Prehistoric Park, which filmed in the same location, and their upcoming Surviving Earth also filmed in the same place again, but at least it seems it's not Hell Creek this time ), but there's no evidence of this, nor was there ever. The only real evidence of volcanism in the region that I could find was ash likely thrown up by the asteroid impact ; if there ever was any volcanism in the region, it was at typical levels at best, nothing like what was shown. While there was a period of intense volcanism during the Maastrichtian, it was happening in the Deccan Traps of India, literally on the opposite side of the planet. How much this affected the biosphere is also heavily up for debate; WWD presents the idea dinosaurs were already on their way out due to climate change and the asteroid simply hastened the inevitable, but this hypothesis was contentious even then, and most studies since refute it (also the exact date of the extinction probably occurred around 66 MYA, rather than 65.5 MYA, as previously thought).

Part of this is likely due to a sampling bias; most research done on Late Maastrichtian biota is North America-centric, but it's clear the continent was unusual in terms of dinosaur diversity. Unlike the other continents, sauropods were present in only one known species and instead most of the ecosystems were dominated by giant ceratopsians. Another part was something about non-avian dinosaur and pterosaur physiology that has only come to light in the last decade or so; their growth patterns were not like that of modern mammals or most birds, they grew slowly and juveniles and adolescents filled different niches from adults , unlike birds and mammals were they grew rapidly and juveniles/adolescents eat the same stuff as adults. By the Late Cretaceous, many dinosaurs and pterosaurs had become truly gargantuan and had evolved immature life stages which filled the niches previously filled by medium-sized species , resulting in a drop in perceived diversity. This was also likely a reason they became completely extinct, as the absent of smaller, faster-growing species, the result of a highly successful evolutionary strategy in a stable ecosystem, was now suddenly a death sentence for the groups now that food was beyond scarce and day-by-day survival was Herculean in the months following the impact. Only those small, fast-growing animals that required little food and those which could shelter within the relatively stable freshwater ecosystems were able to eke out a living during this cataclysm.

Far from the depiction of an ashy wasteland, the Hell Creek region was a lush, swamp-like forest habitat that bordered the receding Western Interior Seaway. This environment is distinct from anything that exists today; at this time, Montana was much further north than it is today, resulting in more extreme seasonal shifts, but the warm, humid climate of the time prevented cold winters, allowing subtropical plants and animals like crocodilians and palm trees to thrive. The ebb of the seasons was therefore only evident by the dramatic differences in daylight and night time between mid-summer and mid-winter. Such an environment was host to some of the grandest and most spectacular fauna to have ever lived on Earth, the very last non-avian dinosaurs, which thrived in dozens of species, ranging from enantiornitheans smaller than crows to hadrosaurs twice as heavy as a full-grown elephant. In the coastal waters swam immense marine lizards, the mosasaurs, and the skies above were darkened by the largest wings of any flying animal. When this habitat disappeared, never again would life on land ever exist at such a scale.

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Tyrannosaurus rex: The protagonist of this episode. The Walking with franchise has this tendency to choose the coolest animals over more reasonable animals, and here it's made evident by the fact they picked the main character to be the largest and most fearsome predator ever known to have walked the Earth. Reaching over twelve-metres in length, Tyrannosaurus was the undisputed apex predator of the region; no other terrestrial carnivore known from the continent came even remotely close. Improved mass and volume estimate methods since the 1990s, which put Tyrannosaurus' mass at about five tonnes, have since increased its weight to a staggering ten metric tonnes for the largest known individuals. A disproportionate amount of research has been poured into this species, resulting in far more known of it in the time since WWD. Tyrannosaurus had superb senses, with exceptional eyesight , hearing , and smell , even among all known animals. Jaws up to five feet long could inflict the most powerful bite of any land animal to ever live , with foot-long spike-like teeth allowing it to crush bone and tear flesh with great efficiency, an exceptionally powerful and vital weapon when hunting the giant, often armoured, herbivores it coexisted with.

So it's a bit of a shame the WWD reconstruction of Tyrannosaurus is really ugly, hideous even. While a lot of the animals have very wonky proportions and questionable anatomy, the Tyrannosaurus really takes the cake , especially because this isn't some obscure taxon known from a few dissociated scraps, so there's no excuse for its execution. The skull is a grotesque chunky block with an inexplicable frill at the back and bulging lips, the tail is unnaturally thin and short, arms are too large, the legs are way too long (which is really saying something because Tyrannosaurus already had long legs for a theropod its size), the neck is way too thin for such a huge head, there's a too narrow chest/torso, wrinkly elephant-like skin for no reason (skin impressions described since indicate tiny, rounded scale over at least portions of the body ), and it has utterly bizarre hoof-like feet. Almost every aspect of its anatomy is messed up, Jurassic Park's Tyrannosaurus is miles better by comparison, and this may rank among the worst-looking popular Tyrannosaurus restorations ever, although, if nothing else, it's definitely distinct and unique (those aren't necessarily positive descriptors).

Their Tyrannosaurus has these weird ridges above the eyes, which, according to supplementary text, is based on the idea that the pairs of bony knobs above its eyes were the base of a large single crest. This is a very obscure idea, so obscure I didn't even know it was ever an idea, although it is present in some older paleoart , but I don't think the idea is followed by anyone these days because there's basically no evidence for it beyond saying "maybe it's possible". The episode states that Tyrannosaurus females are larger and more fearsome than males; this was an idea based on a study of crocodilian chevrons (the bony arch on the bottom of the tail verterbrae) supposedly showing that females had a reduced chevron to make way for the egg canal. This was seemingly found in Tyrannosaurus too, such as in "Sue", the largest specimen known at the time and an extremely robust morph, suggesting that females were the larger sex. However, the idea was later discredited two-fold; the evidence of the reduced crocodilian chevron was found to be misinterpreted, and Sue in fact had a fully-intact chevron , meaning there's no evidence to suggest females were larger than males. It's not implausible, but it's equally possible that males were the larger sex or that both sexes were the same size. The social habits of Tyrannosaurus are almost entirely speculative at this point, but they were pretty mean to one another at times .

Gypsonictops hypoconus: I don't plan on getting into Walking with Beasts, but at least I'll show the animals that appeared in the opening prologue of that series, which is set in the Hell Creek Formation at the end of the Cretaceous. This amounts to two additional small mammals, showing how the group was evolutionarily limited by the grand success of the dinosaurs (and assorted other reptiles). This is one of those two mammals, a lepticidan, made from recycling the Leptictidium model, showing how the group was around in the Cretaceous (sort of; it's been established now the group is paraphyletic in respect to placental mammals). The portrayal here, as an elephant shrew-like animal, is extremely speculative as the species is known only from teeth .

Alphadon marshi: The small, dead thing that was seen suffocated by the volcanic gases steaming out of underground vents. The identity of this animal is never mentioned so I picked a random small mammal from the region which could resemble it, specifically this genus also appeared in the Walking with Dinosaurs movie, although it had a more opossum-like appearance, probably due to its ancestry as a metatherian.

Coniophis precedens: Making a brief appearance in the episode is a snake (live-acted by a boa constrictor) which is curiously investigated by the Tyrannosaurus chicks. This is meant to illustrate how snakes had only recently appeared at the time (on an evolutionary time scale), although in practice it makes me think the producers ran short on the runtime and just stuffed in a random modern day animal (a lot cheaper than having to include more CG animals). The snake species is unmentioned in the episode, but it may or may not coincidentally reference an unnamed species of boid known from the Hell Creek Formation, the earliest known species of boid in fact, although supplementary material state it's supposed to be Dinilysia, despite this taxon living ten million years older in South America. However, due to lack of references, I've picked a different species of more primitive snake from the region, which had some better information regarding scale and appearance (even though the "appearance" here is rough due to having to scale with dinosaurs).

Didelphodon vorax: The only (named) mammal featured in the series, representing the rise of such small furry animals in the twilight of the dinosaurs' reign, although Didelphodon and the other stagodontids did not survive to prosper during the Cenozoic. The restoration of Didelphodon in the show little resembles its current appearance, in large part due to its fragmentary nature at the time; it was only known from its teeth and parts of the jaw and skull, which showed that it was a relatively large mammal with a powerful bite, evolved for crushing hard foodstuffs (indeed, pound-for-pound, this was the most powerful known bite of any mammal to have ever existed ). This resulted in the speculative appearance of a similarly robust body, creating a badger or Tasmanian devil-like animal, but much more complete fossils showed the polar opposite, restoring Didelphodon as a lithe and slenderly built mammal , resulting in an otter-like animal, possibly semi-aquatic animal, about a metre in length.

Melvius thomasi: The identity chosen for the random generic fish that the pterosaur snatches up and eats. Hell Creek, fittingly enough, was a very lush ecosystem, and most of the region was latticed by countless rivers and streams that flowed into the Western Interior Seaway. This environment allowed for an incredibly rich diversity of aquatic animals, from several crocodilians, more than a dozen turtle species, the gharial-like choristodere Champsosaurus, numerous freshwater hesperornitheans, the giant sirenid Habrosaurus, a number of freshwater sharks, and of course many, many species of ray-finned fish, some reaching huge proportions. The most common ray-finned fish was a species of bowfin, Cyclurus fragosus, but this is a much larger and less common species. Growing up to five feet long , this is far, far larger than the modern bowfin species, but it was itself dwarfed by the sturgeons and paddlefish which it coexisted with. It would have certainly been a formidable aquatic hunter, but it was far from the largest predator around...

Tyrannosaurus rex (infant): Although the baby of Tyrannosaurus has appeared very often in dinosaur media, almost nothing is actually known about this stage of a tyrannosaur's life. All we have from this stage of their life is a jawbone and one toe claw (only described in 2021 at that), rendering their actual appearance almost completely speculative. What we know we reconstruct from older adolescent animals, and other dinosaur species for which hatchlings are known, showing an animal with a small body, long legs, and a narrow snout. Fossils from many stages of a Tyrannosaurus' life, from two to about thirty years old, are known, showing a life cycle which is not followed by any large mammalian predators; most of their lifespan was spent in an extended adolescence that spanned about eighteen years. Although a full-grown animal could've reached over ten metric tonnes, it took more than a full decade to even reach one ton, at which point Tyrannosaurus entered a form of "puberty", with its growth rate rocketing until eventually plateauing again at around twenty. At any one time, adolescent animals probably made up the majority of the Tyrannosaurus population alive, particularly as most adult fossils are of individuals that died only a few years after reaching maturity, suggesting high infant and adult, but low juvenile, mortality rates . The life of a Tyrannosaurus, the ultimate predator, was one where only the best of the best lived to see old age.

Meniscoessus robustus: This is another animal based on something which appeared in the opening of WWB, a small, squirrel-like mammal (played by a squirrel). It's never mentioned specifically what sort of animal it is, not surprising considering the brevity of the prologue and the obscurity of Mesozoic mammals, but I've picked out a multituberculate species from Hell Creek. Multituberculates were rodent-like non-eutherian mammals; they had the same pair of similar gnawing incisors, but differed in their chewing method, moving their teeth back to front rather than side to side. They thrived during the age of the dinosaurs and survived into the Cenozoic, but became extinct during the Eocene; this was one of the largest Mesozoic species, reaching up to eight pounds, so it was easier for it to actually show up discernibly in this parade.

Torosaurus latus (juvenile): I'll go into greater detail about Torosaurus as a species below, and this part focuses most on just the juvenile part. Remains of Torosaurus juveniles are nonexistence (part of why it's sometimes argued as a growth stage of Triceratops), so the version here is mostly based on Triceratops, the most reasonable choice possible under the circumstances, because, growth stage or not, Triceratops is basically its closest relative and the young of closely related animals tend to look almost identical. The frill of young Triceratops were swept back, curving upwards as they grew, and the brow horns began as nubs, while the epoccipitals (the spikes that lined the edge of the frill in ceratopsids) were larger and spikier, becoming comparatively smaller and much more rounded as they matured. Strangely, the horns curved upwards initially, curving back down to form an S-shape as they approached adulthood, and then in some of the older animals, curving all the way down (although there was a lot of individual variation). I haven't seen any technical ideas on why, but maybe it was easier to stab upwards when small and downwards when big.

Triceratops prorsus (adolescent): For some bizarre reason, Triceratops, the most common large animal of Laramidia and one of the most iconic dinosaurs is reduced to a role of a half-eaten corpse in WWD, and its role is replaced with the much rarer and more obscure Torosaurus. This is genuinely one of the most baffling choices WWD ever made, especially once you consider Triceratops makes up almost half of all dinosaur fossils from Hell Creek , and Torosaurus was so rare it was a small fraction of one percent. Did the valley the episode is set have 90% of all Torosaurus in Hell Creek? The only explanation I've ever seen to possibly explain it is that this is yet another example of WWD going for spectacle over realism; Torosaurus had the largest known skull of any terrestrial animal, with a massive frill (although some Triceratops skulls were not far behind). And that's basically it, the only thing Torosaurus has over Triceratops, since they were virtually identical otherwise.

The documentary states that the individual killed by the male Tyrannosaurus was "young", which is a vague term and the carcass shown seems to be a subadult at the least (which is not really young). For the purpose of showing more growth patterns in ceratopsids, I've interpreted "young" as being an actual immature animal, with upward-curving horns and prominent epoccipitals still (although I also drew an adult version on Patreon). Animals such as this would've been prime Tyrannosaurus chow, as an actual full-grown Triceratops was a formidable foe, capable of weighing over ten tonnes. Unlike many ceratopsids, and especially unusual for a chasmosaurine, its frill was solid, lacking the large fenstrae present in other species, allowing it to be used as a defensive shield. Although tooth marks also show it made for a handy grip for Tyrannosaurus feeding on its carcass; the bite patterns suggest that the predator got at the tastiest neck muscles by gripping the frill with its teeth and ripping the head clean off . Considering the incredibly powerful bite of Tyrannosaurus, and its ability to crush and eat bone (known from probable coprolites ), the state of the Triceratops corpse in the show once it's been "finished" is remarkably intact (reminds me of that viral image of the "demolished" chicken wings ). Although I assume effects limitations are to blame for that.

Acheroraptor temertyorum*: An unidentified dromaeosaur appears in the episode, which is identified as Dromaeosaurus itself in supplementary material, although probably referred to with a generic title because Dromaeosaurus is only definitively known from earlier Campanian deposits. The dromaeosaur is a grey-scaled re-skin of the Utahraptor, although its shape is based on Deinonychus, so we got a mish-mashed generic raptor overall. The reason for this is that dromaeosaur remains from Hell Creek were generally poor at the time, consisting mostly of just individual teeth, some of which were tentatively assigned to Dromaeosaurus. Indeed, Acheroraptor, the first named dromaeosaur from the formation , is still only known from a partial dentary and mandible, although many of the assorted Hell Creek dromaeosaur teeth were tentatively assumed to actually belong to Acheroraptor, including the ones previously thought to belong, maybe, to Dromaeosaurus. So here, Dromaeosaurus is replaced with Acheroraptor.

Here's where we get to an elephant in the room which has nothing to do with WWD. Only two years after Acheroraptor was described and thought to be the only confirmed dromaeosaur from Hell Creek, a second dromaeosaur species was described from the site, and it made a much bigger splash (SVP 2023 presented a third possible unenlagiine or halszkaraptorine from Hell Creek, but it's extremely scrappy and not important here so I won't get into it). This is of course, Dakotaraptor, apparently a gigantic dromaeosaur which filled the mid-sized predator niche in between small dromaeosaurs/azhdarchids/troodontids and adolescent Tyrannosaurus. However, its very existence has been subject to intense scrutiny and heavily debated; its supposed fossils are quite scattered and fragmentary, and were found in a huge jumble of different bones of various animals, its supposed wishbone was later confirmed to be a carapace fragment from a softshell turtle (specifically Axestemys). Other remains are also questionable, with other suggestions that different pieces may actually derive from juvenile Tyrannosaurus, ornithomimid, and large oviraptorosaur (probably Anzu) remains. Only one vertebrae actually seems to come from a dromaeosaur , and its size suggests an animal much smaller than the Utahraptor-sized animal Dakotaraptor was scaled as. This restoration of Acheroraptor uses the informal suggestion that the vertebrate could just have likely come from a large Acheroraptor (as the holotype represents an immature animal, often the case for dinosaurs), around the size of Deinonychus (although I did draw a version with Dakotaraptor on Patreon, just in case).

Ankylosaurus magniventris: The largest and last of the thyreophorans, the ultimate culmination of a hundred million years of honed defensive capabilities against carnivorous dinosaurs, and this one built to withstand one of the most formidable predators to ever walk the Earth. WWD has a strange-looking Ankylosaurus, but I can't really blame them because, for such a famous dinosaur, it's not got that good a fossil record (although, thanks to its incredibly durable and heavily constructed bones, the skull is known) and the ideas of its armour arrangement are notoriously varied and complex , and very few portrayals have gotten it right (and maybe still haven't, it's largely speculative). The armour arrangement seen in WWD is in fact based on an illustrated diagram by Barnum Brown in 1908, which should give you an idea how poorly known Ankylosaurus armour orientation is if they're using an illustration 90 years old. So not only are its large osteoderms much more varied and widely spaced (it can't be seen here, but the spaces in between them would've been filled with many small osteoderms), its back is much flatter than the turtle-like form seen in the show, its face is less weird-looking, and its tail club is a lot less lumpy (sorry it got covered a bit here, it was really hard to get as much of every animal visible as possible, but you can see the full versions of every animal on Patreon).

Interestingly, the last several vertebrae in their tails were interlocking , often fused, and straightened by numerous ossified tendons. This rendered the second half of the tail completely immobile, with as much flexibility as a plank of wood, and only the base of the tail could bend. This of course made the club an even better battering weapon, as it meant very little of the force driving each tail swing would be lost when it made contact with its target, hitting with the maximum amount of impact (whether that be against attacking predators or each other).

Edmontosaurus annectens: The animal formerly known as Anatotitan, formerly known as Anatosaurus, formerly known as Trachodon, formerly known (partly) as Claosaurus.... This was one of the last and largest of the hadrosaurs, sometimes informally known as the "duck-billed dinosaurs". This nickname is very misleading however, for the simple reason that hadrosaurs did not actually have duck bills (and of course ducks are duck-billed dinosaurs too). Many older restorations, like that of WWD, neglected to consider something that was not conclusively known until later , that the duck-bill shape of the snout was only the shape of the bone, and there would've been a keratinous beak over top of this bone that changed its shape in life. A preserved rhamphotheca shows that the wide snout was hidden under a downward-facing keratin sheath. Also, the snout was narrower in younger animals, so the duck-billed skull did not appear until the animal was about ten years old.

The Anatotitan in the show is pretty obviously another recycled model, Iguanodon with a different head in this case, giving it the same anatomical traits that belonged on Iguanodon that don't belong on a hadrosaur (and then these inaccuracies got carried over to Chased by Dinosaurs with the Saurolophus, which is just Anatotitan with a small crest, with the same skin patterns too). Most obviously, the overly bulky forelimbs, which have individual toes and thumb spikes, something hadrosaurs did not have. Hadrosaurs had very gracile forelimbs (it's been suggested this helped them navigate through crowded nesting colonies) and an exceptionally well preserved Edmontosaurus front foot shows it had a single horse hoof-like nail that touched the ground (plus a small clawed finger and clawless finger which didn't). Hadrosaur skin impressions found since also show a "frill" of skin running along the back (this was incorporated into the Edmontosaurus design for the WWD film, which looks much better overall).

This is another work that portrays hadrosaurs as defenceless tyrannosaur fodder, but this must've been a formidable target as an adult, since they were about the same size as Tyrannosaurus (sometimes even larger ). Just because it didn't have any sort of armour or spikes doesn't mean it has no way to defend itself, especially when this is an animal that could weight more than an elephant. With that sort of mass behind it, any sort of attack has the potential to cause catastrophic damage, blunt force or otherwise. This restoration is about average adult size, but a few fossils suggest they can rarely grow to bigger sizes, potentially making Edmontosaurus one of the largest non-sauropod dinosaurs.

Thescelosaurus neglectus: Briefly seen in the episode are a pair of generic smallish ornithopods briefly pursued by the unnamed dromaeosaur. This is by far the laziest use of prop recycling in the series, as it is 100% the Othnielia models, with zero attempt to even slightly change the colours and patterns. As far as I know, the animals in the episode have never been formally identified in any supplementary material, strangely, but given the process of elimination, the only real candidate is Thescelosaurus, since that's the only smallish ornithopod known from the region and time ("small" is relative here, of course, as this animal could grow over four metres long). Thescelosaurus was a common dinosaur from Hell Creek, making up about 8% of dinosaur fossils; given its much smaller size, it might've been the most common non-avian dinosaur in the ecosystem at the time, although there was more than one species.

I've restored Thescelosaurus here with a partially feathered coat, which is speculative, but it falls within the realm of possibility, as the regions in where scales (the legs) are known are still left scaly. I've also restored it with a feature only very recently found, spurs on the forelimbs , from a study presented at SVP 2022, which suggests their presence for violent intraspecific combat, like those of modern gamefowl. There's also evidence to suggest that Thescelosaurus was a burrowing animal (not that surprising, since it was a relative of Oryctodromeus), although I can't really show that here. All in all, there is much to indicate it was much more than a generic prey animal.

Torosaurus latus: The token ceratopsid of the episode.... and of the entire series. As previously stated, the episode provides a very skewed view of Hell Creek biota by presenting Torosaurus as the most common ceratopsid and Tyrannosaurus' primary prey, when in actuality seemed to have been an extremely rare animal. Aside from what I've already stated above, the main issue is again its elephantine feet; as stated several times prior, dinosaurs did not have these. Another addition to all three ceratopsid restorations here is the discovery of skin impressions from Triceratops is that its body was covered in very large polygonal scales, some of which were nipple-shaped, with small points. Given the very close relation of Torosaurus with Triceratops (indeed, their post-cranial skeletons are basically identical), I think it would be likely their integument patterns are also similar, if not the same. A somewhat speculative feature here are the inflatable nasal sacs; ceratopsids had unusually large and complex sinuses , the purposes of which are still unknown, so I've gone for the default suggestion of a display feature, although a large number of restorations just choose to ignore it.

Thoracosaurus neocesariensis: A rather unusual inclusion in the episode is an unnamed "one-ton crocodile", not just because no such animal is known from Hell Creek, but because it's a bright orange crocodile and its only role is to be a menacing floating head in the water. Supplementary material identifies it as Deinosuchus, but that of course is probably why it's not named in the show, since it not only doesn't resemble Deinosuchus (with an unusually gharial-like skull and rows of osteoderms(?) on the head for some reason), it's about ten million years beyond its temporal range. The only crocodyliforms from the time period were of a much more typical size range; Deinosuchus' closest relative from Hell Creek, the alligatoroid Brachychampsa, would've only been about eight or nine feet long.

So I've replaced it with the largest crocodyliform actually known for certain from the region, the gharial-like Thoracosaurus, which can reach over fifteen feet in length, large by modern standards, but nothing exceptional in the fossil record, and it would not have been any real threat to any of the other large animals in the episode (although, it would've been about the same weight as the pterosaur, unbelievably). Deinosuchus was also portrayed as much smaller than it really is; far from being "one-ton" (about the weight of a particularly large saltwater crocodile), Deinosuchus was one of the largest crocodilians of all time (a true crocodilian in this case, related to modern alligators and caimans, not one of the many non-crocodilian crocodylomorphs that were around in the Mesozoic), and would've weighed about as much as an African elephant. The other option was a large mosasaur, which are known from Hell Creek , and were very common worldwide at the time, but I decided to keep it as a crocodile-line animal for taxonomic closeness.

Quetzalcoatlus northropi: One of the biggest animals to ever take to the skies (sorry Ornithocheirus/Tropeognathus), Quetzalcoatlus was an immense pterosaur, standing as tall as a giraffe, with a probable wingspan of over ten metres (what's more, the wingspan was small relative to the animal's body size, unlike Tropeognathus' huge soaring wings), only rivalled in size by some contemporary azhdarchid species. Wingspan estimates at the time were much cruder due to the poor knowledge of azhdarchid anatomy, sometimes going over fifteen metres in width (the show went for a more conservative thirteen metres, but even that seems too big these days). This is the only animal here not definitively known from the Hell Creek region; at best the neck vertebrae of an indeterminate mid-sized azhdarchid is known , which is assumed to be Quetzalcoatlus, but it can't be identified so specifically (and even if it is Quetzalcoatlus, it could be the much smaller Q. lawsoni rather than Q. northropi), although given the fact Quetzalcoatlus could fly, its presence in Hell Creek seems plausible enough. It's already presented as being a vagrant in the episode, but from the ocean, which is strange because its fossils aren't known from the coastal region. Quetzalcoatlus' known range was the southern portion of Laramidia, where the forested swamplands of Hell Creek opened into a semi-arid savannah; Torosaurus became more common, Edmontosaurus was replaced by Kritosaurus, Acheroraptor was replaced by Dineobellator, and most significantly, the ecology of the region was dominated by the giant titanosaur Alamosaurus, the only sauropod species known from North America during the Late Cretaceous.

This is one of many clumsy Quetzalcoatlus portrayals over the decades, as the anatomy of the azhdarchids was not well-studied until relatively recently. This is made worse by the fact Quetzalcoatlus is another recycled model (as is every large pterosaur in the show), rather crudely modified from the Ornithocheirus, so much so that it has teeth in its beak (they at least avoid showing the beak in focus to hide the teeth). Of course, its real proportions were incredibly bizarre, with a gigantic head, an extremely long neck, and a tiny body. It's also shown as another crawling fish-eater that is a fish out of water on land (and they avoid showing it taking off, noticeably) and the very last of a dying breed. At the time it was thought that Quetzalcoatlus might have been an aerial fish-eater, replacing the older hypothesis that it was a vulture-like scavenger, but both ideas are now replaced by the widely accepted theory that azhdarchids were land-based foraging predators like giant storks or herons, and were highly mobile on land. Also, it's now well-known azhdarchids were one of the most successful and widespread animal groups at the end of the Late Cretaceous, with their fossils known from every continent except maybe Antarctica, ranging in numerous sizes and shapes, and also lived alongside various species of pteranodontian pterosaurs, which also persisted until the very end of the Mesozoic in multiple species .

*(if the name has an asterisk next to it, that signifies that the species had not yet been formally described at the time of the show's original airing)

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Anatomical References Used:

Tyrannosaurus rex (1 )
Didelphodon vorax (1 )
Triceratops prorsus (adolescent) (1 )
Triceratops prorsus (1 )
Acheroraptor temertyorum (1 )
Ankylosaurus magniventris (1 )
Edmontosaurus annectens (1 )
Thescelosaurus neglectus (1 )
Dakotaraptor steini (1 )
Torosaurus latus (1 )
Thoracosaurus neocesariensis (1 )
Quetzalcoatlus northropi (1 )

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Description
SETTING: Montana, Late Maastrichtian (66 MYA)

And here we move to the final episode of the original series (and a bit of a segue into the prologue of the sequel episode), where we return to North America for the fourth time, a few months before the fated asteroid is about to merge Heaven and Earth, bringing about the end of the age of reptiles. Despite what they may tell you, dinosaurs were continuing to flourish on every continent (well, we don't really know what was happening on Australia, but probably dinosaurs were still dominating there) in great diversity, size, and numbers. The episode presents an incredibly skewed and dubious view of Hell Creek, showing intense volcanism rendering much of the region an inhospitable wasteland (repeated in the Impossible Picture's spiritual follow-up Prehistoric Park, which filmed in the same location, and their upcoming Surviving Earth also filmed in the same place again, but at least it seems it's not Hell Creek this time ), but there's no evidence of this, nor was there ever. The only real evidence of volcanism in the region that I could find was ash likely thrown up by the asteroid impact ; if there ever was any volcanism in the region, it was at typical levels at best, nothing like what was shown. While there was a period of intense volcanism during the Maastrichtian, it was happening in the Deccan Traps of India, literally on the opposite side of the planet. How much this affected the biosphere is also heavily up for debate; WWD presents the idea dinosaurs were already on their way out due to climate change and the asteroid simply hastened the inevitable, but this hypothesis was contentious even then, and most studies since refute it (also the exact date of the extinction probably occurred around 66 MYA, rather than 65.5 MYA, as previously thought).

Part of this is likely due to a sampling bias; most research done on Late Maastrichtian biota is North America-centric, but it's clear the continent was unusual in terms of dinosaur diversity. Unlike the other continents, sauropods were present in only one known species and instead most of the ecosystems were dominated by giant ceratopsians. Another part was something about non-avian dinosaur and pterosaur physiology that has only come to light in the last decade or so; their growth patterns were not like that of modern mammals or most birds, they grew slowly and juveniles and adolescents filled different niches from adults , unlike birds and mammals were they grew rapidly and juveniles/adolescents eat the same stuff as adults. By the Late Cretaceous, many dinosaurs and pterosaurs had become truly gargantuan and had evolved immature life stages which filled the niches previously filled by medium-sized species , resulting in a drop in perceived diversity. This was also likely a reason they became completely extinct, as the absent of smaller, faster-growing species, the result of a highly successful evolutionary strategy in a stable ecosystem, was now suddenly a death sentence for the groups now that food was beyond scarce and day-by-day survival was Herculean in the months following the impact. Only those small, fast-growing animals that required little food and those which could shelter within the relatively stable freshwater ecosystems were able to eke out a living during this cataclysm.

Far from the depiction of an ashy wasteland, the Hell Creek region was a lush, swamp-like forest habitat that bordered the receding Western Interior Seaway. This environment is distinct from anything that exists today; at this time, Montana was much further north than it is today, resulting in more extreme seasonal shifts, but the warm, humid climate of the time prevented cold winters, allowing subtropical plants and animals like crocodilians and palm trees to thrive. The ebb of the seasons was therefore only evident by the dramatic differences in daylight and night time between mid-summer and mid-winter. Such an environment was host to some of the grandest and most spectacular fauna to have ever lived on Earth, the very last non-avian dinosaurs, which thrived in dozens of species, ranging from enantiornitheans smaller than crows to hadrosaurs twice as heavy as a full-grown elephant. In the coastal waters swam immense marine lizards, the mosasaurs, and the skies above were darkened by the largest wings of any flying animal. When this habitat disappeared, never again would life on land ever exist at such a scale.

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Tyrannosaurus rex: The protagonist of this episode. The Walking with franchise has this tendency to choose the coolest animals over more reasonable animals, and here it's made evident by the fact they picked the main character to be the largest and most fearsome predator ever known to have walked the Earth. Reaching over twelve-metres in length, Tyrannosaurus was the undisputed apex predator of the region; no other terrestrial carnivore known from the continent came even remotely close. Improved mass and volume estimate methods since the 1990s, which put Tyrannosaurus' mass at about five tonnes, have since increased its weight to a staggering ten metric tonnes for the largest known individuals. A disproportionate amount of research has been poured into this species, resulting in far more known of it in the time since WWD. Tyrannosaurus had superb senses, with exceptional eyesight , hearing , and smell , even among all known animals. Jaws up to five feet long could inflict the most powerful bite of any land animal to ever live , with foot-long spike-like teeth allowing it to crush bone and tear flesh with great efficiency, an exceptionally powerful and vital weapon when hunting the giant, often armoured, herbivores it coexisted with.

So it's a bit of a shame the WWD reconstruction of Tyrannosaurus is really ugly, hideous even. While a lot of the animals have very wonky proportions and questionable anatomy, the Tyrannosaurus really takes the cake , especially because this isn't some obscure taxon known from a few dissociated scraps, so there's no excuse for its execution. The skull is a grotesque chunky block with an inexplicable frill at the back and bulging lips, the tail is unnaturally thin and short, arms are too large, the legs are way too long (which is really saying something because Tyrannosaurus already had long legs for a theropod its size), the neck is way too thin for such a huge head, there's a too narrow chest/torso, wrinkly elephant-like skin for no reason (skin impressions described since indicate tiny, rounded scale over at least portions of the body ), and it has utterly bizarre hoof-like feet. Almost every aspect of its anatomy is messed up, Jurassic Park's Tyrannosaurus is miles better by comparison, and this may rank among the worst-looking popular Tyrannosaurus restorations ever, although, if nothing else, it's definitely distinct and unique (those aren't necessarily positive descriptors).

Their Tyrannosaurus has these weird ridges above the eyes, which, according to supplementary text, is based on the idea that the pairs of bony knobs above its eyes were the base of a large single crest. This is a very obscure idea, so obscure I didn't even know it was ever an idea, although it is present in some older paleoart , but I don't think the idea is followed by anyone these days because there's basically no evidence for it beyond saying "maybe it's possible". The episode states that Tyrannosaurus females are larger and more fearsome than males; this was an idea based on a study of crocodilian chevrons (the bony arch on the bottom of the tail verterbrae) supposedly showing that females had a reduced chevron to make way for the egg canal. This was seemingly found in Tyrannosaurus too, such as in "Sue", the largest specimen known at the time and an extremely robust morph, suggesting that females were the larger sex. However, the idea was later discredited two-fold; the evidence of the reduced crocodilian chevron was found to be misinterpreted, and Sue in fact had a fully-intact chevron , meaning there's no evidence to suggest females were larger than males. It's not implausible, but it's equally possible that males were the larger sex or that both sexes were the same size. The social habits of Tyrannosaurus are almost entirely speculative at this point, but they were pretty mean to one another at times .

Gypsonictops hypoconus: I don't plan on getting into Walking with Beasts, but at least I'll show the animals that appeared in the opening prologue of that series, which is set in the Hell Creek Formation at the end of the Cretaceous. This amounts to two additional small mammals, showing how the group was evolutionarily limited by the grand success of the dinosaurs (and assorted other reptiles). This is one of those two mammals, a lepticidan, made from recycling the Leptictidium model, showing how the group was around in the Cretaceous (sort of; it's been established now the group is paraphyletic in respect to placental mammals). The portrayal here, as an elephant shrew-like animal, is extremely speculative as the species is known only from teeth .

Alphadon marshi: The small, dead thing that was seen suffocated by the volcanic gases steaming out of underground vents. The identity of this animal is never mentioned so I picked a random small mammal from the region which could resemble it, specifically this genus also appeared in the Walking with Dinosaurs movie, although it had a more opossum-like appearance, probably due to its ancestry as a metatherian.

Coniophis precedens: Making a brief appearance in the episode is a snake (live-acted by a boa constrictor) which is curiously investigated by the Tyrannosaurus chicks. This is meant to illustrate how snakes had only recently appeared at the time (on an evolutionary time scale), although in practice it makes me think the producers ran short on the runtime and just stuffed in a random modern day animal (a lot cheaper than having to include more CG animals). The snake species is unmentioned in the episode, but it may or may not coincidentally reference an unnamed species of boid known from the Hell Creek Formation, the earliest known species of boid in fact, although supplementary material state it's supposed to be Dinilysia, despite this taxon living ten million years older in South America. However, due to lack of references, I've picked a different species of more primitive snake from the region, which had some better information regarding scale and appearance (even though the "appearance" here is rough due to having to scale with dinosaurs).

Didelphodon vorax: The only (named) mammal featured in the series, representing the rise of such small furry animals in the twilight of the dinosaurs' reign, although Didelphodon and the other stagodontids did not survive to prosper during the Cenozoic. The restoration of Didelphodon in the show little resembles its current appearance, in large part due to its fragmentary nature at the time; it was only known from its teeth and parts of the jaw and skull, which showed that it was a relatively large mammal with a powerful bite, evolved for crushing hard foodstuffs (indeed, pound-for-pound, this was the most powerful known bite of any mammal to have ever existed ). This resulted in the speculative appearance of a similarly robust body, creating a badger or Tasmanian devil-like animal, but much more complete fossils showed the polar opposite, restoring Didelphodon as a lithe and slenderly built mammal , resulting in an otter-like animal, possibly semi-aquatic animal, about a metre in length.

Melvius thomasi: The identity chosen for the random generic fish that the pterosaur snatches up and eats. Hell Creek, fittingly enough, was a very lush ecosystem, and most of the region was latticed by countless rivers and streams that flowed into the Western Interior Seaway. This environment allowed for an incredibly rich diversity of aquatic animals, from several crocodilians, more than a dozen turtle species, the gharial-like choristodere Champsosaurus, numerous freshwater hesperornitheans, the giant sirenid Habrosaurus, a number of freshwater sharks, and of course many, many species of ray-finned fish, some reaching huge proportions. The most common ray-finned fish was a species of bowfin, Cyclurus fragosus, but this is a much larger and less common species. Growing up to five feet long , this is far, far larger than the modern bowfin species, but it was itself dwarfed by the sturgeons and paddlefish which it coexisted with. It would have certainly been a formidable aquatic hunter, but it was far from the largest predator around...

Tyrannosaurus rex (infant): Although the baby of Tyrannosaurus has appeared very often in dinosaur media, almost nothing is actually known about this stage of a tyrannosaur's life. All we have from this stage of their life is a jawbone and one toe claw (only described in 2021 at that), rendering their actual appearance almost completely speculative. What we know we reconstruct from older adolescent animals, and other dinosaur species for which hatchlings are known, showing an animal with a small body, long legs, and a narrow snout. Fossils from many stages of a Tyrannosaurus' life, from two to about thirty years old, are known, showing a life cycle which is not followed by any large mammalian predators; most of their lifespan was spent in an extended adolescence that spanned about eighteen years. Although a full-grown animal could've reached over ten metric tonnes, it took more than a full decade to even reach one ton, at which point Tyrannosaurus entered a form of "puberty", with its growth rate rocketing until eventually plateauing again at around twenty. At any one time, adolescent animals probably made up the majority of the Tyrannosaurus population alive, particularly as most adult fossils are of individuals that died only a few years after reaching maturity, suggesting high infant and adult, but low juvenile, mortality rates . The life of a Tyrannosaurus, the ultimate predator, was one where only the best of the best lived to see old age.

Meniscoessus robustus: This is another animal based on something which appeared in the opening of WWB, a small, squirrel-like mammal (played by a squirrel). It's never mentioned specifically what sort of animal it is, not surprising considering the brevity of the prologue and the obscurity of Mesozoic mammals, but I've picked out a multituberculate species from Hell Creek. Multituberculates were rodent-like non-eutherian mammals; they had the same pair of similar gnawing incisors, but differed in their chewing method, moving their teeth back to front rather than side to side. They thrived during the age of the dinosaurs and survived into the Cenozoic, but became extinct during the Eocene; this was one of the largest Mesozoic species, reaching up to eight pounds, so it was easier for it to actually show up discernibly in this parade.

Torosaurus latus (juvenile): I'll go into greater detail about Torosaurus as a species below, and this part focuses most on just the juvenile part. Remains of Torosaurus juveniles are nonexistence (part of why it's sometimes argued as a growth stage of Triceratops), so the version here is mostly based on Triceratops, the most reasonable choice possible under the circumstances, because, growth stage or not, Triceratops is basically its closest relative and the young of closely related animals tend to look almost identical. The frill of young Triceratops were swept back, curving upwards as they grew, and the brow horns began as nubs, while the epoccipitals (the spikes that lined the edge of the frill in ceratopsids) were larger and spikier, becoming comparatively smaller and much more rounded as they matured. Strangely, the horns curved upwards initially, curving back down to form an S-shape as they approached adulthood, and then in some of the older animals, curving all the way down (although there was a lot of individual variation). I haven't seen any technical ideas on why, but maybe it was easier to stab upwards when small and downwards when big.

Triceratops prorsus (adolescent): For some bizarre reason, Triceratops, the most common large animal of Laramidia and one of the most iconic dinosaurs is reduced to a role of a half-eaten corpse in WWD, and its role is replaced with the much rarer and more obscure Torosaurus. This is genuinely one of the most baffling choices WWD ever made, especially once you consider Triceratops makes up almost half of all dinosaur fossils from Hell Creek , and Torosaurus was so rare it was a small fraction of one percent. Did the valley the episode is set have 90% of all Torosaurus in Hell Creek? The only explanation I've ever seen to possibly explain it is that this is yet another example of WWD going for spectacle over realism; Torosaurus had the largest known skull of any terrestrial animal, with a massive frill (although some Triceratops skulls were not far behind). And that's basically it, the only thing Torosaurus has over Triceratops, since they were virtually identical otherwise.

The documentary states that the individual killed by the male Tyrannosaurus was "young", which is a vague term and the carcass shown seems to be a subadult at the least (which is not really young). For the purpose of showing more growth patterns in ceratopsids, I've interpreted "young" as being an actual immature animal, with upward-curving horns and prominent epoccipitals still (although I also drew an adult version on Patreon). Animals such as this would've been prime Tyrannosaurus chow, as an actual full-grown Triceratops was a formidable foe, capable of weighing over ten tonnes. Unlike many ceratopsids, and especially unusual for a chasmosaurine, its frill was solid, lacking the large fenstrae present in other species, allowing it to be used as a defensive shield. Although tooth marks also show it made for a handy grip for Tyrannosaurus feeding on its carcass; the bite patterns suggest that the predator got at the tastiest neck muscles by gripping the frill with its teeth and ripping the head clean off . Considering the incredibly powerful bite of Tyrannosaurus, and its ability to crush and eat bone (known from probable coprolites ), the state of the Triceratops corpse in the show once it's been "finished" is remarkably intact (reminds me of that viral image of the "demolished" chicken wings ). Although I assume effects limitations are to blame for that.

Acheroraptor temertyorum*: An unidentified dromaeosaur appears in the episode, which is identified as Dromaeosaurus itself in supplementary material, although probably referred to with a generic title because Dromaeosaurus is only definitively known from earlier Campanian deposits. The dromaeosaur is a grey-scaled re-skin of the Utahraptor, although its shape is based on Deinonychus, so we got a mish-mashed generic raptor overall. The reason for this is that dromaeosaur remains from Hell Creek were generally poor at the time, consisting mostly of just individual teeth, some of which were tentatively assigned to Dromaeosaurus. Indeed, Acheroraptor, the first named dromaeosaur from the formation , is still only known from a partial dentary and mandible, although many of the assorted Hell Creek dromaeosaur teeth were tentatively assumed to actually belong to Acheroraptor, including the ones previously thought to belong, maybe, to Dromaeosaurus. So here, Dromaeosaurus is replaced with Acheroraptor.

Here's where we get to an elephant in the room which has nothing to do with WWD. Only two years after Acheroraptor was described and thought to be the only confirmed dromaeosaur from Hell Creek, a second dromaeosaur species was described from the site, and it made a much bigger splash (SVP 2023 presented a third possible unenlagiine or halszkaraptorine from Hell Creek, but it's extremely scrappy and not important here so I won't get into it). This is of course, Dakotaraptor, apparently a gigantic dromaeosaur which filled the mid-sized predator niche in between small dromaeosaurs/azhdarchids/troodontids and adolescent Tyrannosaurus. However, its very existence has been subject to intense scrutiny and heavily debated; its supposed fossils are quite scattered and fragmentary, and were found in a huge jumble of different bones of various animals, its supposed wishbone was later confirmed to be a carapace fragment from a softshell turtle (specifically Axestemys). Other remains are also questionable, with other suggestions that different pieces may actually derive from juvenile Tyrannosaurus, ornithomimid, and large oviraptorosaur (probably Anzu) remains. Only one vertebrae actually seems to come from a dromaeosaur , and its size suggests an animal much smaller than the Utahraptor-sized animal Dakotaraptor was scaled as. This restoration of Acheroraptor uses the informal suggestion that the vertebrate could just have likely come from a large Acheroraptor (as the holotype represents an immature animal, often the case for dinosaurs), around the size of Deinonychus (although I did draw a version with Dakotaraptor on Patreon, just in case).

Ankylosaurus magniventris: The largest and last of the thyreophorans, the ultimate culmination of a hundred million years of honed defensive capabilities against carnivorous dinosaurs, and this one built to withstand one of the most formidable predators to ever walk the Earth. WWD has a strange-looking Ankylosaurus, but I can't really blame them because, for such a famous dinosaur, it's not got that good a fossil record (although, thanks to its incredibly durable and heavily constructed bones, the skull is known) and the ideas of its armour arrangement are notoriously varied and complex , and very few portrayals have gotten it right (and maybe still haven't, it's largely speculative). The armour arrangement seen in WWD is in fact based on an illustrated diagram by Barnum Brown in 1908, which should give you an idea how poorly known Ankylosaurus armour orientation is if they're using an illustration 90 years old. So not only are its large osteoderms much more varied and widely spaced (it can't be seen here, but the spaces in between them would've been filled with many small osteoderms), its back is much flatter than the turtle-like form seen in the show, its face is less weird-looking, and its tail club is a lot less lumpy (sorry it got covered a bit here, it was really hard to get as much of every animal visible as possible, but you can see the full versions of every animal on Patreon).

Interestingly, the last several vertebrae in their tails were interlocking , often fused, and straightened by numerous ossified tendons. This rendered the second half of the tail completely immobile, with as much flexibility as a plank of wood, and only the base of the tail could bend. This of course made the club an even better battering weapon, as it meant very little of the force driving each tail swing would be lost when it made contact with its target, hitting with the maximum amount of impact (whether that be against attacking predators or each other).

Edmontosaurus annectens: The animal formerly known as Anatotitan, formerly known as Anatosaurus, formerly known as Trachodon, formerly known (partly) as Claosaurus.... This was one of the last and largest of the hadrosaurs, sometimes informally known as the "duck-billed dinosaurs". This nickname is very misleading however, for the simple reason that hadrosaurs did not actually have duck bills (and of course ducks are duck-billed dinosaurs too). Many older restorations, like that of WWD, neglected to consider something that was not conclusively known until later , that the duck-bill shape of the snout was only the shape of the bone, and there would've been a keratinous beak over top of this bone that changed its shape in life. A preserved rhamphotheca shows that the wide snout was hidden under a downward-facing keratin sheath. Also, the snout was narrower in younger animals, so the duck-billed skull did not appear until the animal was about ten years old.

The Anatotitan in the show is pretty obviously another recycled model, Iguanodon with a different head in this case, giving it the same anatomical traits that belonged on Iguanodon that don't belong on a hadrosaur (and then these inaccuracies got carried over to Chased by Dinosaurs with the Saurolophus, which is just Anatotitan with a small crest, with the same skin patterns too). Most obviously, the overly bulky forelimbs, which have individual toes and thumb spikes, something hadrosaurs did not have. Hadrosaurs had very gracile forelimbs (it's been suggested this helped them navigate through crowded nesting colonies) and an exceptionally well preserved Edmontosaurus front foot shows it had a single horse hoof-like nail that touched the ground (plus a small clawed finger and clawless finger which didn't). Hadrosaur skin impressions found since also show a "frill" of skin running along the back (this was incorporated into the Edmontosaurus design for the WWD film, which looks much better overall).

This is another work that portrays hadrosaurs as defenceless tyrannosaur fodder, but this must've been a formidable target as an adult, since they were about the same size as Tyrannosaurus (sometimes even larger ). Just because it didn't have any sort of armour or spikes doesn't mean it has no way to defend itself, especially when this is an animal that could weight more than an elephant. With that sort of mass behind it, any sort of attack has the potential to cause catastrophic damage, blunt force or otherwise. This restoration is about average adult size, but a few fossils suggest they can rarely grow to bigger sizes, potentially making Edmontosaurus one of the largest non-sauropod dinosaurs.

Thescelosaurus neglectus: Briefly seen in the episode are a pair of generic smallish ornithopods briefly pursued by the unnamed dromaeosaur. This is by far the laziest use of prop recycling in the series, as it is 100% the Othnielia models, with zero attempt to even slightly change the colours and patterns. As far as I know, the animals in the episode have never been formally identified in any supplementary material, strangely, but given the process of elimination, the only real candidate is Thescelosaurus, since that's the only smallish ornithopod known from the region and time ("small" is relative here, of course, as this animal could grow over four metres long). Thescelosaurus was a common dinosaur from Hell Creek, making up about 8% of dinosaur fossils; given its much smaller size, it might've been the most common non-avian dinosaur in the ecosystem at the time, although there was more than one species.

I've restored Thescelosaurus here with a partially feathered coat, which is speculative, but it falls within the realm of possibility, as the regions in where scales (the legs) are known are still left scaly. I've also restored it with a feature only very recently found, spurs on the forelimbs , from a study presented at SVP 2022, which suggests their presence for violent intraspecific combat, like those of modern gamefowl. There's also evidence to suggest that Thescelosaurus was a burrowing animal (not that surprising, since it was a relative of Oryctodromeus), although I can't really show that here. All in all, there is much to indicate it was much more than a generic prey animal.

Torosaurus latus: The token ceratopsid of the episode.... and of the entire series. As previously stated, the episode provides a very skewed view of Hell Creek biota by presenting Torosaurus as the most common ceratopsid and Tyrannosaurus' primary prey, when in actuality seemed to have been an extremely rare animal. Aside from what I've already stated above, the main issue is again its elephantine feet; as stated several times prior, dinosaurs did not have these. Another addition to all three ceratopsid restorations here is the discovery of skin impressions from Triceratops is that its body was covered in very large polygonal scales, some of which were nipple-shaped, with small points. Given the very close relation of Torosaurus with Triceratops (indeed, their post-cranial skeletons are basically identical), I think it would be likely their integument patterns are also similar, if not the same. A somewhat speculative feature here are the inflatable nasal sacs; ceratopsids had unusually large and complex sinuses , the purposes of which are still unknown, so I've gone for the default suggestion of a display feature, although a large number of restorations just choose to ignore it.

Thoracosaurus neocesariensis: A rather unusual inclusion in the episode is an unnamed "one-ton crocodile", not just because no such animal is known from Hell Creek, but because it's a bright orange crocodile and its only role is to be a menacing floating head in the water. Supplementary material identifies it as Deinosuchus, but that of course is probably why it's not named in the show, since it not only doesn't resemble Deinosuchus (with an unusually gharial-like skull and rows of osteoderms(?) on the head for some reason), it's about ten million years beyond its temporal range. The only crocodyliforms from the time period were of a much more typical size range; Deinosuchus' closest relative from Hell Creek, the alligatoroid Brachychampsa, would've only been about eight or nine feet long.

So I've replaced it with the largest crocodyliform actually known for certain from the region, the gharial-like Thoracosaurus, which can reach over fifteen feet in length, large by modern standards, but nothing exceptional in the fossil record, and it would not have been any real threat to any of the other large animals in the episode (although, it would've been about the same weight as the pterosaur, unbelievably). Deinosuchus was also portrayed as much smaller than it really is; far from being "one-ton" (about the weight of a particularly large saltwater crocodile), Deinosuchus was one of the largest crocodilians of all time (a true crocodilian in this case, related to modern alligators and caimans, not one of the many non-crocodilian crocodylomorphs that were around in the Mesozoic), and would've weighed about as much as an African elephant. The other option was a large mosasaur, which are known from Hell Creek , and were very common worldwide at the time, but I decided to keep it as a crocodile-line animal for taxonomic closeness.

Quetzalcoatlus northropi: One of the biggest animals to ever take to the skies (sorry Ornithocheirus/Tropeognathus), Quetzalcoatlus was an immense pterosaur, standing as tall as a giraffe, with a probable wingspan of over ten metres (what's more, the wingspan was small relative to the animal's body size, unlike Tropeognathus' huge soaring wings), only rivalled in size by some contemporary azhdarchid species. Wingspan estimates at the time were much cruder due to the poor knowledge of azhdarchid anatomy, sometimes going over fifteen metres in width (the show went for a more conservative thirteen metres, but even that seems too big these days). This is the only animal here not definitively known from the Hell Creek region; at best the neck vertebrae of an indeterminate mid-sized azhdarchid is known , which is assumed to be Quetzalcoatlus, but it can't be identified so specifically (and even if it is Quetzalcoatlus, it could be the much smaller Q. lawsoni rather than Q. northropi), although given the fact Quetzalcoatlus could fly, its presence in Hell Creek seems plausible enough. It's already presented as being a vagrant in the episode, but from the ocean, which is strange because its fossils aren't known from the coastal region. Quetzalcoatlus' known range was the southern portion of Laramidia, where the forested swamplands of Hell Creek opened into a semi-arid savannah; Torosaurus became more common, Edmontosaurus was replaced by Kritosaurus, Acheroraptor was replaced by Dineobellator, and most significantly, the ecology of the region was dominated by the giant titanosaur Alamosaurus, the only sauropod species known from North America during the Late Cretaceous.

This is one of many clumsy Quetzalcoatlus portrayals over the decades, as the anatomy of the azhdarchids was not well-studied until relatively recently. This is made worse by the fact Quetzalcoatlus is another recycled model (as is every large pterosaur in the show), rather crudely modified from the Ornithocheirus, so much so that it has teeth in its beak (they at least avoid showing the beak in focus to hide the teeth). Of course, its real proportions were incredibly bizarre, with a gigantic head, an extremely long neck, and a tiny body. It's also shown as another crawling fish-eater that is a fish out of water on land (and they avoid showing it taking off, noticeably) and the very last of a dying breed. At the time it was thought that Quetzalcoatlus might have been an aerial fish-eater, replacing the older hypothesis that it was a vulture-like scavenger, but both ideas are now replaced by the widely accepted theory that azhdarchids were land-based foraging predators like giant storks or herons, and were highly mobile on land. Also, it's now well-known azhdarchids were one of the most successful and widespread animal groups at the end of the Late Cretaceous, with their fossils known from every continent except maybe Antarctica, ranging in numerous sizes and shapes, and also lived alongside various species of pteranodontian pterosaurs, which also persisted until the very end of the Mesozoic in multiple species .

*(if the name has an asterisk next to it, that signifies that the species had not yet been formally described at the time of the show's original airing)

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Anatomical References Used:

Tyrannosaurus rex (1 )
Didelphodon vorax (1 )
Triceratops prorsus (adolescent) (1 )
Triceratops prorsus (1 )
Acheroraptor temertyorum (1 )
Ankylosaurus magniventris (1 )
Edmontosaurus annectens (1 )
Thescelosaurus neglectus (1 )
Dakotaraptor steini (1 )
Torosaurus latus (1 )
Thoracosaurus neocesariensis (1 )
Quetzalcoatlus northropi (1 )

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