Tyrantrum is a large, dinosaurian Pokémon, closely resembling theropods like Tyrannosaurus. It is predominantly brick-red in coloration, with scaly patterns on its skin and scattered orange highlights on some of the scales and ridges. The underbelly is gray with white borders, and it has a long tail with two orange spikes near the tip. Its small forelimbs have only two black clawed digits, but it has powerful hind legs with three sharp, black talons. Plated, armor-like ridges are found on the front of the legs and down the back and tail. Spiky, white "fluff", similar to the primitive feathers on many dinosaurs, extends into a cape-like fringe around the neck.
Additional feathering forms a prominent beard on the lower jaw, which is otherwise gray in coloration. Its head is proportionally large, with a ridged snout and powerful jaws. The lower jaw is lined with pointed teeth, and the upper jaw features a number of tooth-like projections which are also highlighted orange. Its eyes appear to have black sclera with white irises. An orange, five-pointed crest extends from the snout above the eyes and point backwards, giving it the appearance of wearing a crown.
Before its extinction, wild Tyrantrum used to live 100 million years ago, when its powerful jaw conferred its status as an unmatched predator. It is theorized that in its time, its whole body was covered with a feather-like coat. Since it was considered invincible in the ancient world, it behaved like a king.
Four Tyrantrum debuted in The Tiny Caretaker!, under the ownership of several Scientists, with one of them having evolved from a Tyrunt. Bonnie hoped Clemont would catch the Tyrantrum she had befriended, but because the scientists owned it, she had to bid a sad farewell to it.
Tyrantrum is mostly based on the genusTyrannosaurus, though it also shares characteristics (including the orange facial crest) with the Carnosauria clade. The orange crest is also similar to those seen on Cryolophosaurus. The orange crest and white feathers may also have been inspired by kings (with the crest acting as the crown, the fringe on the lower jaw acting like a beard, and the fringe on the Pokémon's neck acting as a cape). The fringe may also be a reference to the possibility of Tyrannosaurus having feathers.
Tyrantrum may be a combination of Tyrannosaurus or tyrant and tantrum.
Gachigoras may be a combination of ガチ gachi (serious or for real) and チゴラス Chigoras (Tyrunt's Japanese name). It may also come from がっちり gacchiri (stocky).
In other languages
Possibly from ガチン gachin, or ガチガチ gachigachi, チゴラス Chigorasu, and Tyrannosaurus