And not just any Sharptooth, but the biggest, meanest, most ferocious Sharptooth ever! (Meanest Sharptooth roaring)
— Grandpa Longneck describing the sharptooth, before it roars.
The "Biggest, Meanest, Most Ferocious Sharptooth Ever" is a legendary Tyrannosaurus rex who appears in Grandpa Longneck's story in The Land Before Time VI: The Secret of Saurus Rock. He bears resemblance to the original Sharptooth and Chomper's father. He also resembles the green sharptooth from the climax of the film. He is said to have fought with the legendary "Lone Dinosaur", and was arguably the meanest and biggest of all Sharpteeth, second only to the original Sharptooth and the Plated Sharptooth.
According to legend, the Sharptooth once came to the Great Valley and attacked a herd of Longnecks. He was about to kill a young one, who got his foot stuck under a stump, when his mother came to save him. Before the sharptooth could clamp his jaws around her neck, the "Lone Dinosaur" showed up to save the two longnecks. The Lone Dinosaur and the Meanest Sharptooth then do battle.
During the fight, he was whipped in the back by the Lone Dinosaur's tail. Angered, he tried twice to slash the Lone Dinosaur, failing the first time. He succeeded the second time, slashing the Longneck across his right eye leaving a long scar all the way down his neck.
As the Sharptooth began to gain the upper hand, pushing the Longneck to the ground, the Lone Dinosaur wrapped his tail around the Sharptooth's legs, sending him crashing into a pile of rocks near the edge of a cliff. As the Sharptooth began to get up, the Lone Dinosaur used his tail to whip him off the cliff, falling to his presumed death.
Supposedly, after Saurus Rock rose from the earth, the teeth of the Sharptooth became a ring of tooth-shaped stones around the monolith.
He later appears in Littlefoot's sleep story the same night that involved him being the Lone Dinosaur. The sharptooth prepares to kill the mother Longneck from the story, before Littlefoot appears on the scene. He leaps from a ground spike, and lands in front of the sharptooth. He whips it in the foot with his tail, causing it to hop on one foot away from the area in pain.
He appears one final time at the end of the film, in Littlefoot and Cera's new story. He prepares to kill the mother Longneck, before being interrupted by The Great Dinosaur (Grandpa Longneck). The Great Dinosaur smiles and walks toward the sharptooth to deal with him.
- Some fans have speculated that the Tyrannosaurus that appears in the climax of the film is the "ghost" of this particular Sharptooth, based on the fact that instead of attacking an Allosaurus intruding on its territory, it turns on Doc and the other Longnecks, and the Allosaurus pays it little notice.
- More evidence is that it appears very close to where the legendary Sharptooth was supposedly killed, and that it very closely resembles it. However, there is no official statement to back up these claims, and the time between the Meanest Sharptooth's defeat and the Tyrannosaurus attacking in the climax would make this unlikely. Moreover, the Tyrannosaurus from the climax did not have the same mouth shape and robust body profile as the Meanest Sharptooth.
- It has also been suggested that the Meanest Sharptooth is Sharptooth himself, although this is unlikely, given the amount of time that passed between the Meanest Sharptooth's defeat, which is thought to be around a century, and the original Sharptooth's death in the first film.
- Some fans also speculate that this sharptooth may be Red Claw from The Land Before Time (TV series). The reason being is that Red Claw may have gotten his scar from falling off the cliff however yet again, the time between the battle and the TV series along with the radically different physical characteristics makes this theory unlikely.
- This is the second character in the franchise, after the Plated Sharptooth, that draws blood onscreen, as he slashes the Lone Dinosaur with his claws.
- This sharptooth is depicted with an abnormally thick neck, a bigger, more exaggerated mouth and teeth and with huge girth compared to other tyrannosaur sharpteeth.
- The scene at the end of the film where the sharptooth appears in the kids' new story takes place in broad daylight with a clear blue sky, instead of the sinister red sky of the Lone Dinosaur story and Littlefoot's sleep story.
- This was possibly done to make the movie more happy and joyful, as the film was near its very end.
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