Screech and Thud

Screech and Thud are a pair of "Fast Biters" (the series' term for dromaeosaurs, or raptor dinosaurs), and the subordinates of Red Claw. Pete Sepenuk plays Screech, while Rob Paulsen plays Thud. They are the secondary antagonists of The Land Before Time television series.

Though no official material confirming their species is known, a number of fans believe that they are depictions of Utahraptor.

Symbiosis with Red Claw
There seems to be a symbiotic relationship between Red Claw, Screech and Thud as Ruby has once said "Wherever Screech and Thud are, Red Claw is never far behind". Also, in at least one episode, "The Hidden Canyon", the Fast Biters led Red Claw to a breach in the wall protecting the Great Valley from Sharpteeth.

In "Return to Hanging Rock", Screech and Thud have been seen hunting without Red Claw. Red Claw appears by himself without them in the same episode, so it seems that they split up from time to time to hunt (or in the fast biters' cases) scout out. This may be why Screech and Thud enter the Valley without their leader.

How or why they hunt together is unknown, though it could do with simple symbiosis: Screech and Thud use their smarts, small size and greater agility to access places Red Claw can't get to when hunting and flush out prey while Red Claw's brute strength and ferocity protects them from being attacked or eaten themselves and guarantees them an easy meal. This is shown in "The Cave of Many Voices" and "Escape From The Mysterious Beyond", as Red Claw had to call in the Fast Biters to chase after the children through areas he could not reach.

Nonetheless, it is almost impossible for Littlefoot and his friends to encounter one without encountering all three and at full strength (barring Red Claw's two final appearances, though they are only cameos and the former is an encounter that only involved Chomper, in the latter he did not find any characters). Nevertheless, they make an incredible, not to mention lethal, team of carnivores.