AsapSCIENCE - The Biggest Paradox on Earth Was Just Solved

Short Summary

Main recommendation: The video's central answer is that the gap in mid-sized carnivorous dinosaurs is explained by juvenile large carnivores, such as young Tyrannosaurus rex, occupying a distinct ecological niche that effectively made them "their own species" in ecological terms. Young megatheropods ate different prey than adults and out-competed other medium-sized dinosaurs, filling the space that would otherwise be occupied by mid-sized predators.

Key Points

• Modern carnivorous land mammals (e.g., from Kruger National Park) are distributed across a fairly even size gradient, while carnivorous dinosaurs from the Dinosaur Park Formation in Alberta show a large gap in the middle sizes.
• Dinosaurs were mostly large: of roughly 1,500 known species, far more exceeded 1,000 kg than were under 60 kg, and very few mid-sized carnivores existed, especially in the Cretaceous period (145.5 to 65 million years ago).
• Egg-laying biology drives the effect: dinosaur hatchlings weighed no more than about 15 kg, while an adult T. rex can reach about 7,000 kg, so babies and adults differed enormously in size and diet.
• Herbivores avoided the same gap because their young could eat the same foliage as adults, and herbivores could partition resources vertically in trees, unlike carnivores who competed with one another.
• When researchers modeled juveniles as separate species, the size gap disappeared, supporting the theory.

Details Worth Noting

• Young T. rex likely could not take on a Triceratops because juveniles were much more slender than adults, becoming bone crushers only after a teenage growth spurt, so they targeted smaller prey.
• A sauropod in the roughly 80-ton range was born at about the size of an average Border Collie, while a giraffe weighs about 68 kg at birth and about 800 kg as an adult.
• Eggs can only be about the size of a football because of how gas is exchanged through the shell, which constrains hatchling size.
• The video's central caveat is that juvenile megatheropods are technically the same species as adults; calling them "their own species" is an ecological framing, not a taxonomic one.

Bottom Line

The mid-size carnivore gap in dinosaur ecosystems is best explained by juvenile large predators competing with and displacing medium-sized dinosaurs, a pattern rooted in how egg-laying dinosaurs grew.