No Triassic-Jurassic mass extinction event: No Dinosaur dominance?

[oshron]

Would crocodiles still evolve the role they did in reality? Or would some other group become semi-aquatic generalists?

actually, there were some terrestrial crocodilians IOTL. one that was around in the Triassic was Postosuchus, which you may remember from the first episode of Walking With Dinosaurs. at a much later time, there was Pristichampsus, which lived in the brief time between the KT Extinction and the rise of mammals

i actually asked a question like this one a long time ago on Jurassic Park Legacy's paleontology forum. one thing that was brought up was that crocodilians as we know them today wouldn't exist, and their roles would be fulfilled by phytosaurs

it's also possible that crocodilians would have evolved some herbivorous forms ITTL if their diversity wasn't limited by the dinosaurs. iirc, there were one or two species like that IOTL but they weren't very prolific

 

[Basileus Giorgios]

closely related Heamatotheria clades

I've never once heard mention of a group called "Heamatotheres". The group you describe is a paraphyletic, not a monophyletic one.

Archosaurs are considerably more closely related to lizards than they are to turtles: but all three groups are sauropsid amniotes. Mammals (and all their extinct relatives) are an entirely different group of amniotes, the synapsids.

Mammals and archosaurs share some features that have allowed the two groups to between them dominate for the better part of three hundred million years, but that's the product of convergent evolution, rather than any particular closeness.