The program has received major criticism due to Horner's negligence to take note of any evidence that might confirm the opposite of his theories, the one-sided approach in the presentation, and the arguments he uses for why Tyrannosaurus was a pure scavenger don't hold up to scrutiny.
The work provides examples of:
- Anachronistic Animal: Saurornitholestes, the dromaeosaurs shown in the program, probably went extinct a few million years before T. rex and Triceratops appeared. Teeth from the Hell Creek Formation previously attributed to Sauronitholestes (tentatively) are now thought to belong to Acheroraptor (named in 2013).
- Animals Not to Scale: The dromaeosaurs in the program are identified as Saurornitholestes, which was around the size of Velociraptor (i.e. the size of a turkey). However, these dromaeosaurs are about as tall as a man, much like the raptors from Jurassic Park (though funnily enough, this predicted the discovery of Dakotaraptor, a man-sized dromaeosaur that lived alongside T. rex, although it should be noted that many scientists consider Dakotaraptor's existence questionable due to its chimeric nature).
- Artistic License – Biology: The program was well constructed and explained in detail why it presented the things the way it has, but paleontologists that happened not to hate Tyrannosaurus may find it to be somewhat infuriating. It doesn't help that he makes several scientifically inaccurate claims and pretty much ignores basic common sense to prove his point.
- Could an animal that size support itself by being lucky enough to constantly bump into still-edible dinosaur carcasses whenever it was hungry? If it is a slow animal, is it possible that maybe it didn't need to be fast because its prey would have been just as slow if not slower? Couldn't it have also just used the element of surprise to catch its food? If it couldn't get up from the ground because of its small arms then how is it supposed to sleep?
- Horner seems to be under the impression that certain scavengers such as vultures look “ugly” because that helps them repel their opposition when stealing their kill. As if wild animals have the same beauty standards as humans or care much about them, to begin with. The iconic bald heads of vultures and condors have instead been theorized to be an adaption for digging into carcasses (reducing the chances of blood sticking to their plumage), or alternatively for thermoregulation (since most species live in hot and arid environments), while their scruffy feather collars help them keep their tucked head and neck warm at night. Those that have wrinkles, wattles, and/or brightly colored skin evolved them as display features, as a sign of fitness and virility (some taking it to the extreme
), and plenty of other birds (many of them not being scavengers or even carnivores) have similar features. - Horner compares T. rex to spotted hyenas for his argument, because everyone knows spotted hyenas are disgusting, cowardly scavengers. Just ignore the literal mountain of nature footage showing spotted hyenas as apex predators. In fact, as predators who rely on the sheer crushing power of their jaws to kill their prey, hyenas actually do make a good comparison to tyrannosaurs.
- Small arms make hunting difficult? Abelisaurs, gorgonopsids, wolves, eagles, monitor lizards, crocodiles, sharks, orcas, literally almost every other large carnivore BUT cats would like a word with you, Mr. Horner. It gets even more egregious considering he cites wolves as a modern counterpart to dromaeosaurids, despite wolves not using their forelimbs at all for hunting.
- Artistic License – Paleontology: Quite a bit, especially considering that a lot of Horner's points in favor of tyrannosaurs being scavengers were countered as far back as 1988's Predatory Dinosaurs Of The World!
- Horner claims that Tyrannosaurus didn't have a very good sense of sight when T. rex is known for having some of the best eyesight of any animal, theorized to be superior even to modern birds-of-prey, never mind dinosaur.
- Horner suggested dromaeosaurs would be the true top predators instead of T. rex, and the documentary proceeds to show them bringing down prey many times their size in numbers. This is, of course, analogous to jackals bringing down an elephant. Admittedly, this was before the discovery of Dakotaraptor, a larger dromaeosaur from the same time as T. rex, but still one way too small (grizzly bear-sized) to bring down animals larger than elephants even in a group. However... The entire idea of pack hunting dromaeosaurs has been brought into question for most varieties as well.
- The documentary claims that T. rex grew to 15 feet tall which is 2 feet taller than the largest specimens that have been discovered. It also claims that the Wynkel specimen was the most complete T. rex skeleton ever found, which is wrong because that title belongs to Sue.
- Both the T. rex and dromaeosaurs have pronated hands, even though it's believed neither were able to hold their hands in such a position.
- The fingers on Horner's Rex are the same length when one should should be shorter than the other.
- T. rex roars like a bear; indeed, the documentary actually uses a stock bear roar sound effect. Whatever vocalizations dinosaurs made probably didn't sound at all mammalian.
- False Dichotomy: Pure hunter or pure scavenger? Why can't T. rex be a bit of both?
- Feathered Fiend: Saurornitholestes and a bunch of other small dromaeosaurs which the rex chases away from their kill.
- Hypocrite: Perhaps the biggest sin the documentary makes. To elaborate:
- Horner does talk about treating science objectively and not letting pop-cultural hype color the image of a real animal like Tyrannosaurus, which is a commendable goal. Claiming T. rex was an unstoppable juggernaut that no other dinosaur could measure up to is extremely disingenuous to the real animal. Like any carnivore, T. rex didn't succeed in every hunt, it wouldn't win every confrontation, it would scavenge any chance it got, needing to avoid starvation as best it can. But he goes too far in trying to temper that overhyped image by insisting it T. rex was the exact opposite, creating a False Dichotomy.
- He also dares anyone to show him evidence that the species wasn't exactly like how he says it was, ignoring evidence well-known at the time such as healed bite wounds on Triceratops indicating predatory behavior, clear indications T. rex was not virtually blind like he says it was, as well as the opinions of multiple other researchers who'd worked on the species, all insisting he's not correct in his assumptions.
- Not helping matters is that he simultaneously overhypes dromaeosaurs as the perfect killing machine as far as dinosaurs go, including being shown taking down prey many times their size, a pop culture stereotype viewed as incredibly sensationalized and inaccurate by actual paleontologists.
- Insult Backfire: The very bulky, redheaded T. rex model we see at the end is meant to invoke Scavengers Are Scum but many viewers found the design to look very badass and intimidating, more so than the standard T. rex design used throughout the bulk of the documentary.
- Irony: Two fold.
- Horner compares T. rex to a spotted hyena only to further support his claim that it was a scavenger. Of course, given that the spotted hyena is actually an accomplished predator in its own right, which kills its prey with its bone-crushing bite, it actually does make a good comparison to T. rex.
- Horner hypes up the Raptor Attack Saurornitholestes and degrades T. rex constantly, with the former as agile, active, intelligent killing-machines and the latter as slow, stupid, and cowardly. And yet in the animation at the end, the mere arrival of a T. rex sends an entire pack of Saurornitholestes running away terrified, making them look cowardly and the T. rex as The Dreaded.
- The Makeover: Inverted. Horner takes a standard CGI Tyrannosaurus and turns it disgustingly ugly — or, in his mind, more realistic. Ironically, this "ugly" design comes across as Informed Deformity, as many viewers found it to be much more awesome and intimidating than the standard design. Doubly ironically, it is now known that Tyrannosaurus was a very bulky animal, so this design actually is more realistic as Horner intended.
- Raptor Attack: The Saurornitholestes are not only oversized, inaccurately feathered, and living in the wrong time period, they were also shown bringing down an Edmontosaurus many times their size and have also managed to kill a Triceratops, against all logic, all while Jack Horner basically fanboys over them as being legit killers unlike T. rex.
- Scavengers Are Scum: The scavenging T. rex as imagined by Horner is depicted in an extremely negative light, in contrast to the nobler image of the classic predatory version.
- Stock Footage: From Discovery's former dinosaur show, When Dinosaurs Roamed America.
- Stock Sound Effects: The roars uttered by the T. rex when it scares away a few smaller theropods from their kill are very obviously modified grizzly bear roars.
- Terrifying Tyrannosaur: Despite making T. rex a pure scavenger in the documentary, it ends with T. rex finding a Triceratops carcass being feasted by Sauronitholestes... and easily scaring them off because of its intimidating size and jaws, a fact that's objectively true in T. rex fossils no matter the debate of predator or scavenger.
- The Worf Effect: A meta-example. What has previously been seen as the ultimate predator is actually a pathetic carrion stealer. At least, that was what the documentary set out to accomplish.
