I found one where Pterano stays bad and it looks like it was called "Quest for Lost Souls" or something.
Also, one called Destiny is kinda dark as Perie died in it and Chomper lost control to his Sharptooth nature and had to leave (no, he didn't kill Petrie).
I found one about some half Sharptooht named Longtail that sounded interesting.
I had my own dark ones.
I had a film XIV where a Pteranodon and Pterodactylus fell in love (despite the fact that the latter was a Sharp Beak) and they had a kid. The Perandon was willing to watch his wife kill Leaf Eaters, even going along on her hunts, though he never helped her attack.
Eventually, the dad realizes that his wife is a narcissist and, though she may have feelings for him, is controlling, and also seems determined to make her son a hunter, despite the dad saying that the choice would be left to the boy (Ptero) and that he didn't want him influenced one way or the other unduly.
His wife, Agatha, got mad when he finally was gonna leave with the boy and lured him away from the nest and murdered and ate him. She then told her son, who was still young and impressionable, that his dad was a Sharptooth and that he was murdered by Leaf Eaters and that they stole the body too. The boy, Ptero, comes to hate Leaf Eaters as he gets older.
He even will hunt on screen, though the death blow won't be shown. (It's interesting as, though we've seen leaf eaters gather food, we've never really seen it from the perspective of the Sharptooth before, other than maybe Chomper in film V.)) Eventually, he gets to the Great Valley and spots the Gang of Five and tries to kill Ducky.
Near the end of the film, he finally finds that he's half leaf eater and his mother, now exposed, reveals what really happened and threatens to kill the Gang of Five (now Ptero's friends) if he doesn't go back with her. The Gang of Five seems willing to die even so he won't have to go back with her.
In my film XV, it's also kinda dark as it reveals that Topps's first wife and Cera's siblings were actually killed by Leaf Eaters (Theehorns) over a food and resource dispute rather than by Sharpteeth, as all the fans had believed. Also, perhaps the villains in here (some theehorns and a one-horn) would have spotted the attack but done nothing and they later come to bully Topps and Topps's father.
In my film XVI, it's a tiny bit dark, as Littlefoot becomes kind of power hungry in this one, even hitting Ducky at one point when she doesn't agree with what he is doing. He wants to feel respected by the grownups and so seeks out a strange rock deep under the Great Valley. He has some shady friends. Littlefoot would even breakup with his real friends in this one, at least for a while.
He'd come close to going after the object, but would realize that what he is doing is wrong. He'd try and back out, but his shady "friends" would kidnap some or all of the Gang of Five as blackmail.
While under there, they'd encounter mammal Sharpteeth (Smilodons). Also, they'd go near underneath the smoking mountains and there would be fire and everything under there.
(It would be LBT's first major cavern scene.)
My LBT 17 part 1 is really dark. It involves an atrocity of a sort committed by Longnecks about 90 years before the Gang of Five was born. Basically, longnecks would go to the Great Valley, which happened, in those days, to be inhabited by T-Rexs, and they wanted the valley for its resources and started killing the inhabitants in the middle of the night.
Eventually, the T-Rexs would fight back and many longnecks would die, including the parents and boyfriend of a younger version of the Old One.
The Sharpteeth would eventually escape out a secret entrance, and go to this place called the Valley of Sharpteeth. They'd later send the Meanest Ever Sharptooth as an assassin but that failed obviously.
It would seem that the two would always be at war (and not just because they are natural enemies).
Things get even darker when a villain rises who is a Bothtooth and knows that omnivores are best suited for survival and thus feels that they should rule over both Leaf Eaters and Sharpteeth. (and maybe Egg Stealers too)
He'd rise to power by first working with Sharpteeth (he needed to work with them anyway, both as he knew they'd be great at subduing Leaf Eaters, and because he could learn their weaknesses that way) and his first partner is the infamous Sharptooht from the first movie.
Their first attack plan would go off right on the night before the Great Earthshake (though they didn't know that was coming.) The villain, posing as a Leaf Eater, misdirected most of the separated herds. It's revealed that he likes both Leaf Eater herds and Sharptooth packs to all stick to their own kinds as they would pose a danger to his new world order if they were to ever work together.
He finds that Grandma and Grandpa Longneck are too tolerant. He also learned kind of, more or less, where Littlefoot and his mother Arianna lived. He decides to whack them first, as they are dangerous to his plans, he believes.
However, Sharptooth ends up going after Littlefoot and Cera and breaking from their plan, and the villain, first trying to delay Mama Longneck, is later forced to fight her to make sure he isn't exposed. As Sharptooth comes along, he actually yells at Sharptooth to kill her, and Sharptooth does. The villain would be in places such that he'd have been out of sight of any of the cameras in the first film.
However, as the villain, who'd been tail whacked by Mama Longneck, and Sharptooht, also tail whacked, go in to attack the three, the Great Earthshake comes.
Eventually, the villain, knowing Mama Longneck must be dead, and believing Cera and Sharptooth to be dead, goes after Littlefoot. However, he loses his and Rooter isn't helpful.
He vows to get Littlefoot and says he's going to take over the world.
Later, he starts killing all over the Mysterious Beyond and even, after putting Chomper in a bad situation, causes the death of the Old One right in the Great Valley itself.
Littlefoot is banished for helping Chomper escape and the villain takes over the Great Valley and starts inflaming racism and gets the Gang of Five to fight each other.
Also, Pterano is shown to have had a role, albeit by mistake, in Petrie's father's death and Petrie seems to not want to ever speak to his uncle ever again.
What is also dark about this one and the next one, the last part of the two part finale, is that Chomper is faced with the difficult decision to possibly be an outcast for life or live life as a regular Sharptooth and a leaf eater hunter.
Also, near the end, the villain is threatening to eat Ali right in front of Litltefoot.
Also, all the nine named villains would return to this one (i.e. Ozzy, Strut, Dil, Ichy, Rinkus, Sierra, Red Claw, Screech, and Thud).
Dil, Ichy, Strut, and Thud would turn nice but Rinkus, Sierra, Red Claw, Ozzy, and Screech would stay bad.
Also, there would be evil Domeheads in this one.
The strange part of this one, though, is that I really changed Gallimimus so that it is a dino-killing omnivore and about 12 feet tall, if not more.
