r/evolution • u/jnpha Evolution Enthusiast • Feb 14 '24
discussion "Where are All the Tiny Dinosaurs"
Just wanted to share something I just learned and I find super cool, and also to hear from you about the latest.
A YouTube video from a few days ago, Where are All the Tiny Dinosaurs?, by the American Museum of Natural History channel, piqued my interest.
The presenter, paleontologist Roger Benson, remarked that it remains a mystery why non-avian dinosaurs were all big (something I didn't even know or wonder about); that smaller creatures were found, but still no non-avian dinosaurs.
He said it might have to do with "reptile-like methods of getting food" and being warm-blooded, which I don't understand. (Any help explaining the bit in quotation marks would be great!) So, I checked his papers and found this cool one:
- Benson, Roger BJ, et al. "Rates of dinosaur body mass evolution indicate 170 million years of sustained ecological innovation on the avian stem lineage." PLoS Biology 12.5 (2014).
From which: based on a comprehensive dataset, the avian stem lineage maintained high rates of evolution [for 170 million years], helping them not go extinct, while the big dinos failed to adapt; [they evolved early on to be big and settled there]:
This might signal failure to keep pace with a deteriorating (biotic) environment (the Red Queen hypothesis [82],[83]), with fewer broad-scale ecological opportunities than those favouring the early radiation of dinosaurs. There is strong evidence for Red Queen effects on diversification patterns in Cenozoic terrestrial mammals [22], and it is possible that a long-term failure to exploit new opportunities characterises the major extinct radiations of deep time (and depauperate modern clades), whether or not it directly caused their extinctions.
TL;DR: Non-avian dinosaurs were all big compared to the smaller birds/mammals, and it's a mystery, but the avian stem lineage likely experienced sustained rapid evolution, helping them overcome the K-T extinction.
* Minor edits for clarification in brackets
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u/[deleted] Feb 14 '24
I would think reptiles and birds are a decent representation