Rinkus and Sierra are the main antagonists of The Land Before Time VII: The Stone of Cold Fire. They were originally friends of Pterano, but appear more sinister than their associate, particularly Sierra, who had to be restrained by Rinkus many times, especially during the song Very Important Creature. They assist in the kidnapping of Ducky, and later attempt to betray Pterano after the "Stone of Cold Fire" turned out to be a powerless meteorite. Some believe that they were burned to death at the end of The Stone of Cold Fire after a volcanic eruption caused the stone to explode; due to the force of the explosion they are last seen careening through the air back to the hollow in the mountain where they had camped the previous night, quite singed and bruised. It is unknown if they survived, however this leaves open the possibility for their return in a sequel if necessary. Many fans believe that they did survive the explosion, as they appear in many fanfics.
Rinkus is at first shown to be the more humorous of the trio, as well as seeming rather giddy with his own ideas. He also first appears cowardly under Pterano's temper; however during Pterano's song "Very Important Creature", he is seen convincing Sierra (who seems altogether ready to kill Pterano immediately) that it would be in their own best interests to tolerate their leader long enough to be lead to their prize; as quoted: "Be patient, let him lead us to the stone." This reveals Rinkus to be more clever and conniving than he was when first presented and that his cowardly nature is just a deception. Rinkus speaks with a deep Cockney accent. His name seems to be a play on the species Rhamphorhynchus.
Sierra is known for his anger issue and has no trouble revealing his cruel, selfish, mutinous, ill-tempered, hot headed and sadistic attitude throughout the film. He is shown being rather impatient, always wanting to take immediate action and never wait. He shows no fear toward Rinkus or Pterano, and repeatedly challenges the latter. On more than one occasion he attempted to physically overthrow Pterano but was always held back by Rinkus. (Rinkus at the time thought they all wanted the same thing and saw no reason for fighting) It is assumed by many that Sierra is actually a sociopath/psychopath, due to his reckless nature, violent temper, having big problems with Pterano, his "leader", pretending to be loyal to gain his goals and having no feeling for anyone but himself, especially had no feeling for the young dinosaurs, for whom he admitted murderous hatred. He always responded to Pterano's sympathy with snide and careless comments like "So what? You should be used to this kind of thing by now." or "Who cares? Once we take over, first thing I'm gonna do is feed them overgrown eggs to the Sharpteeth". Also, when Ducky escapes from the trio, Sierra almost kills her, first by trying to grab her with his talons, and then trying to snap her in his mouth, probably due to his callous hatred of her. His name seems to be a play on the species Cearadactylus.
- They both play a similar role to Ozzy and Strut, Rinkus being voiced by Rob Paulsen, like Strut except more cruel. Also it is left unknown whether either pair survived at the end.
- Interestingly enough, between the angle where they crash into the hollow, and the closeup angle showing them singed and burned, their positions are swapped.
- The Internet Movie Database once mistook Sierra to be in The Land Before Time IX: Journey to Big Water. It has since then been removed from the cast list. Rinkus and Sierra were also once rumored to appear in The Land Before Time XII: The Great Day of the Flyers, but this idea, if ever considered, was apparently dropped, as they are not in the movie.
- Rinkus is the only pterosaur in The Stone of Cold Fire whose species lived during the Jurassic Period.
- Sierra is one of the few characters in the films who made a noise while usually only speaking in leafeater.
- They are actually seen flying into the crowd of farwalkers right after Littlefoot goes to his Grandma.
- Despite being the main antagonists of the film, they were Pterano's henchmen until Pterano reformed.
- They also similar to Sa'Luk from Aladdin 3.
- Both are henchmen that is more sinister than his boss. (Rinkus and Sierra: Pterano, Sa'Luk: Cassim)
- Both try to remove former boss and want to achieve their goals.
- Sierra and Sa'Luk has similar personalities. (Both are rough and hotheaded)
- Sierra is similar to the Sharptooth Flyer from The Land Before Time V: The Mysterious Island, but he has a longer beak and is a lighter shade of brown.
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- Pterano: "If there's one thing I will not tolerate, it's violence!"
- Rinkus: "Then why are you hitting me?"
- —Rinkus questioning Pterano's hypocritical actions
- Ducky: "You are not very good at landing, are you?"
- Sierra: "Pipe down, or I'll-"
- Pterano: "Sierra! Show a little self control, will you?"
- Sierra: "Self control my tail-bone! I've been puttin' up with that whiny little voice since we took off! (imitating Ducky) "No, no, no! Yep, yep, yep!" (In normal voice) It's driving me *nuts*, *nuts*, *nuts!*"
- —Sierra mocking and showing his dislike for Ducky's speech patterns and voice
- Rinkus: "Look, no one is coming after us. Maybe we can leave our guest here, and be on our way, yes?"
- Ducky: "Oh, I would not do that if I were you. No, no, no."
- Rinkus: "Leave you behind?"
- Ducky: "No, stand on that edge." (The ledge Rinkus is standing on crumbles and he falls off the cliff)
- Ducky: "Told him."
- —Rinkus suggesting to leave Ducky behind, only to fall of the ledge he was standing on.
- Pterano: "Ducky, can you hear me? Come out now child, I promise, we won't hurt you."
- Sierra: "Heh-heh, yeah, musta' been quite a drop."
- —Sierra showing his complete lack of concern for Ducky's safety
- Pterano: "Oh dear, I hope the children were able to find cover."
- Sierra: "Who cares? Once we take over first thing I'm gonna do is feed them overgrown eggs to the Sharptooth!"
- —Sierra showing his hatred toward the main characters