WWD: Tyrannosaurus rex (Infant) (Patreon)

Since the T. rex babies are also a not insignificant part of the episode, I'll include them here too. Despite tyrannosaur babies commonly appearing in popular dinosaur media, disappointingly little is actually known of them. In fact, the only verifiable tyrannosaur infant fossils were only described in 2021 and consists of an isolated jaw, tooth, and toe claw. Most depictions are therefore based on a 1970 hypothetical restoration of Gorgosaurus hatchling by Dale Russell (probably best known for his troodontid humanoid idea).

The issue is that, although Tyrannosaurus adults were gigantic, all dinosaurs hatched from comparatively puny eggs and had tiny offspring. Even the largest sauropods, animals that could exceed 80 tonnes in weight, entered the world only about the size of a cat. Small bones of such tiny animals preserve much less than large bones. So while we have bones from Tyrannosaurus ranging from two years to thirty years old, nothing is known from hatchlings or even yearlings. What we do know of tyrannosaur growth indicates their juvenile stage was extended, they reached a sort of "puberty" at around age 13-14, growing rapidly (as in, gaining close to one ton a year) until around 16-18 years old, when growth plateaued.

Legs of juveniles were proportionately elongate, and this, together with the arctometatarsal condition (an adaptation of the foot bones which help distribute force while running) likely suggests their lifestyle as extraordinarily speedy hunters, preying on smaller, faster animals than adults (perhaps animals like Ornithomimus and Thescelosaurus). Their snouts were also much longer and thinner than in adults, and they did not develop the robust, bone-crushing skull until close to their twenties. Indeed, the remains of juvenile T. rex were in the past considered to belong to "dwarf tyrannosaur" taxa because they were so different, Nanotyrannus and Stygivenator. They likely hatched precocious and independence from parental care probably occurred at an early age. Life would have been extremely harsh for newborn T. rex, but those few that survived their first year would have a good shot of reaching adulthood, at which point predation would become a nonissue.