The origins of tetrapods

[Halichoeres]

Here's a nice review of the origins of the tetrapod gait based on body fossils and trackways. The trackways show up before the body fossils, which suggests that they were around for a while before we find any of their actual anatomy preserved. They probably just lived in places where fossilization potential was poor, like ephemeral water bodies and inland basins.

A visual summary:



Paper (open access): https://www.cambridge.org/core/services/aop-cambridge-core/content/view/03CDF19859875BB5F43B6AB81C5E476A/S1755691018000695a.pdf/follow_the_footprints_and_mind_the_gaps_a_new_look_at_the_origin_of_tetrapods.pdf