Ancient crocodiles walked on two legs like dinosaurs

I saw a fun talk on crocs a few years back. It's not an area that gets much research funding. One concept stuck with me...

Crocodilians used to come in a variety of sizes, including small. Now all (adults) are large. There was a bottleneck, and the survivors use infrasound for mating calls. Which is great for long-range rendezvous - elephants can sing for kilometers. But crocs can't make their long-wavelength call if they're too short. So they've been trapped large.

Brief: https://www.youtube.com/watch?v=ZIxl10Qvgw8 BBC Earth: https://www.youtube.com/watch?v=SlLuC7257pc