In the closed forests of subterramundus, a close relative of the giant tyrants has taken a new approach to hunting in a different environment. In the dense foliage of these regions a smaller, more slender body plan proved more successful than the robust body of a fully grown tyrannosaur.
Microtyrannus is a diminutive tyrannosaur that might appear highly derived from its larger relatives. However, when compared to the juveniles of giants like therosaurus, the relation becomes clear. Rather than evolving a smaller body size, microtyrannus is descended from an ancestor that became neotenic, reaching sexual maturity early in its life and permanently remaining in a teenager morph to avoid competition with larger tyrannosaurs.
The closest relative of microtyrannus is therosaurus, a connection that is most evident in the shape of their teeth and gular pouch.
The defining features of adult microtyrannus that set them apart from juvenile therosaurs are the long pointed horns and brightly coloured throat and gular sacs in the males. Therosaurus only attain these features at 18 to 20 years of age, by which time they are several times larger than a fully grown microtyrannus. Microtyrannus reach maturity and develop these features at around 10 years old.
In distant regions of Subterramundus that lack stable populations of therosaurus, microtyrannus could grow into a robust morph which would greatly reassemble the titan hunter save for some divergent colouration. These giants would share sauropod hunting adaptations and habits of therosaurs but would also take other prey like ornithischians.