The Mystery of the Missing Tiny Dinosaurs

Publication Info:

Transcript:

Stephanie C. Lechki & Roger B.J. Benson. The explanatory power of energetic fitness models across living amniotes and extinct non-avian dinosaurs. Evolution, published online August 5, 2026; doi: 10.1093/evolut/qpag117

Have you ever wondered whether aren't any tiny dinosaurs? There are obviously small non avian dinosaurs, but nothing truly tiny has ever been found, and that's weird. Some brand new research is looking into the physical limitations of multiple animal groups, including dinosaurs, and may now know why they couldn't get too small. Hint: it may be our fault

Episode 325

Notes:

Have you ever wondered why there aren't any small dinosaurs? I mean, there are small non-avian dinosaurs, animals like Compsognathus, but there aren't any like tiny non-avian dinosaurs. The smallest species get down around 450 g, or the size of a modern rabbit, which means that especially compared to their modern bird relatives, non-avian dinosaurs just didn't get that small, and that's weird. There were no non-avian weevils or flowerpeckers or hummingbirds, and you'd think that a group that got so large that they were literally the largest animals to ever live on land on our planet, and got down to like that 450-g line, you'd think that they could get smaller, right? Well, some brand new research is looking into that, and they may have found the answer. Using a mathematical model for energetic fitness, researchers just compared body mass data from mammals, birds, lizards, snakes, turtles, crocodilians, and 515 non-avian dinosaurs. They then used statistical regression to calculate acquisition and conversion constants for each group, then used their projected body size distribution, and compared those numbers to the actual animals, and found that it was at least mostly consistent in most of the groups, and they couldn't find any combination of realistic physiological characters that would limit non-avian dinosaurs to such a large minimum size. Meaning that for at least some of the time non-avian dinosaurs were around the limitation could have been us. And I do mean that, because according to the researchers, the most likely limitation came from the ecosystem and competition from other animals, including once they were around, mammals, which have multiple times gotten really good at getting really small. As usual, if you want more information, here's the source.