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[[caption-width-right:350:If you thought ''Film/{{Jaws}}'' was scary...]]
There are several gruesome and terrifying scenes throughout the series.
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* New Blood: It's not surprising if any kid back in 1999 that saw the series for the first time has been scared by the death of [[spoiler: the baby cynodont who wandered too far]] and the look on [[spoiler: the ''Postosuchus''' face as she dies (she's drooling, and her eyes are ''blood red'')]].
* In a deleted scene in the US program: the couple of adult cynodonts '''eat their own young''' to have more possibilities to escape predators. Since there isn't any fossil proof about this behaviour, [[{{Squick}} was it really necessary to show it]]?
* "Cruel Sea". Just..."Cruel Sea". It's not surprising if it didn't make a whole lot of people not want to go anywhere near any coastlines for a while... in particular, that part where the bitten-off ''Opthalmosaurus'' tail slowly sinks to the sea floor is what did it for many people.
** ''Liopleurodon'' is ''the'' definition of a SeaMonster, managing to make the shark from ''Film/{{Jaws}}'' look like a sardine in comparison. Its size in the series may have been greatly exaggerated (''Liopleurodon'' is actually 20 feet long, but the show depicted it as big as 75 feet long), but that still doesn't make it any less scary (in fact, you could probably say that the size exaggeration was actually ''[[RuleOfScary intentional]]'').
** It doesn't help that his design makes him look as though he has a perpetual SlasherSmile.
** The ''Liopleurodon's'' death, [[CruelAndUnusualDeath seeing as after he's beached he's slowly crushed underneath his own weight]].
* A deleted scene from the original: [[{{Squick}} the dead tyrannosaur embryo out of the broken egg]].
** Worse still, someone apparently thought it was a good idea to restore this scene in the DVD version.
* The scene just before the meteorite hits:
** Everything just seems to stop. The baby ''T. rex'' look out into the distance. The ''Anatotitan'' and ''Torosaurus'' herds look up at the sky. The ''Dromaeosaurus'' runs for cover. And then there's a huge flash of bright light, as the narrator explains the meteorite has struck Earth offscreen. We see the baby ''rexes'' looking into the distance at the bright light, accompanied by numerous other calls from other animals, including one that literally sounds like a child screaming in terror. The light dies down, then the shockwaves begin, rocking the Earth violently. Finally, within moments, the blast from the meteorite begins peeking out over some distant mountains as the animals of the region continue to cry out in terror. The babies are helplessly flung away by the wind, and are followed by their dead mother. The final scene set in prehistoric times is a rain of molten fire.
-->'''Narrator''': This is the ''end'' of the age of the dinosaurs.
** The ''Prehistoric Planet'' version of the scene also expands on the scene right before the meteorite arrives, describing the dinosaurs as being able to sense approaching danger, but they just don't know what to do and are completely helpless in their final moments.
* Earlier in "Death of a Dynasty", the battle at night between the dromeosaurid pack and the ''Torosaurus'' herd. The raptors successfully wound a baby ''Torosaurus'', who flees to the safety of the herd. However, morning comes and reveals that the baby succumbed to its injuries. We then get a shot of its body almost entirely stripped to the bone, leaving only its head and limbs intact.
** Right before the fight, we see a meteor shower that the narrator makes clear is a harbinger of the approaching meteorite.
* The ''Koolasuchus'' from "Spirits of the Ice Forest". A huge carnivorous amphibian that acts something like a crocodile.
* The giant ants in ''Walking with Beasts'' which devour the chick alive, depicting how the chick struggles to hatch from its egg as the ants swarm all over body and then the skeleton of the chick [[TearJerker when the mother returns]], caused many viewers to hate not only ''the entire ant lineage'', but even ant-scientists and ant-lovers since watching this scene. Zoologists and environmentalists have to [[SarcasmMode thank]] ''Walking With'' a lot.
** From the same episode, the giant flightless bird ''Gastornis'' killing its prey. It does it by ''shaking it to death'' while giving off strangled shrieks that are almost growls. The death is so drawn-out and just plain savage that it manages to be truly brutal even though it's BloodlessCarnage - though you ''do'' hear the SickeningCrunch of its neck vertebrae being snapped.
* Some scavengers in the series seem to like to eat ''[[EyeScream the eyes]]'' of the corpses. And the female ''Dimetrodon'' loses an eyeball after a fight.
* The agony of the armoured herbivore ''Scutosaurus'' killed by the mammal-like gorgonopsid in ''WWM'': you can see the blood of the former gushing out of its neck!
* ''Walking With Cavemen'' may as well be retitled "Walking with Nightmare Fuels" as well, it's full of these from the start to the end... especially about the exaggerated realism of some death scenes.
* The fact that some of our ancestors in the program are portrayed with a rather... [[UncannyValley grotesque look]] makes this program even more scary. That means that we are descendants of Nightmare Fuels. Every person that you see every day, including you, is descended from those Nightmare Fuels. So we are surrounded by Nightmare Fuel every day. Come to think of it, Walking With Cavemen could also count as [[FridgeHorror Fridge Horror]].
** Our earliest ancestors shown, Australopithecus afarensis, look like something right out of a horror film. [[http://vignette3.wikia.nocookie.net/walkingwith/images/a/af/Australopithecus_afarensis_img1.jpg/revision/latest?cb=20140109211601 Behold!]]
* Maybe these ancestors ''were not'' so Nightmare Fuelish in RealLife... but producers thought well to make them as scary as possible because of the umpteenth RuleOfCool example. However, see the australopithecine's look in WWB, they are even nice-looking... It seems many WWD continuations ''really like'' to play straight the DarkerAndEdgier trope (not only ''Walking with Monsters''). Anthropologists often say if Neanderthals would be alive today and clothed, they'll pass unnoticed in our modern cities.
** And even then, the ''books'' based on each series are ''worse'', and employ vivid descriptions of other deaths unseen in the series. It's true NothingIsScarier.
* The distressed sounds the ''Iguanodon'' makes and its look of horror when it's being killed by the ''Utahraptor''.
* The whole premise of ''Sea Monsters'' is a group of time-travelers trying to dive with and study very dangerous prehistoric creatures, so there are naturally quite a few scary moments, even though the humorous tone tries to keep it light. Special mention goes to the break between Part 2 and Part 3 where it looks like Nigel has been eaten by a ''C. megalodon'', and TheStinger showing mosasaurs approaching the sonar screen as the crew sleeps.
* From the 3D movie there is the forest fire and the simultaneous ''Gorgosaurus'' attack.
** The following exchange during the forest fire, one of the few times the dialogue isn't too forced.
-->'''Patchi:''' What's fire? Does it eat meat?\\
'''Alex:''' It eats ''everything!'' RUN!
** Scowler getting DrunkWithPower after becoming leader of the herd qualifies as well. When he leaves Patchi to die after saving the herd from a frozen that he himself lead into, it looked like he had become a sociopath.
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