system
Given the following post, respond as if you're commenting on Reddit:
human
Salt Water Crocodiles are said to have changed very little since 'dinosaurs roamed the earth,' is this exclusively because of their apex position in the food chain, or do their offspring show a lower rate of genetic mutation?

As in the title, 'lower rate' as compared to higher mammals, which developed more recently.
gpt
Actually, this is a misconception. What we'd recognise as 'modern crocodiles' actually appeared *after* birds and mammals. It's just that the crocodile body plan has been copied by a lot of their relatives.

The first recognisably crocodilian crocodiles- the eusuchians- evolved about 130 million years ago. Archeopteryx, which is generally considered to be a good example of the first birds, evolved twenty million years earlier. Before that time, crocodiles were small, cat-sized animals.

Their closest relatives, the goniopholids, also looked like crocodiles. The most obvious difference was in their armour- crocodiles have complex patterns of bony lumps (osteoderms) across their backs, while goniopholids had double-rowed plates. They first appeared about two-hundred-million years ago- roughly the same time as the first mammals did.

Earlier than the goniopholid-eusuchian ancestor (the group being neosuchians), most crocodile ancestors were land animals- many, such as Kaprosuchus and Baurusuchus, were easily big enough to hunt dinosaurs. Plant-eaters such as Simosuchus also existed, alongside omnivores, waders and a few 'classic' water-going crocs.

Earlier than goniopholids, you had phytosaurs about two hundred and fifty million years ago- they were so far back in the family tree that a chicken and a croc are more closely related than a croc and a phytosaur. Any further than back and you had killer amphibians such as Eryops, and no crocodile-like animals at all.