There is no next dino. If Erlidom dies from the counterattack after using Strike-and-run, no swap occurs.
And like I said, Tryko will then only “hit in the air” if the move it was going to use affects itself in some way, like if it’s part of a setup (putting up shields, ferocious moves, cleansing moves, etc). Even if an “___-and-run” move isn’t used, if the counter KOs the opponent, the counterattacker will “bite in the air” if the move it was using affects itself, as mentioned above.
For example, if a bleeding Purutaurus takes out its opponent with its counter before it can use cleansing strike, it will use cleansing strike “in the air”.
If a Miragaia takes out its opponent with its counter, it will use Shielded Decelerating strike “in the air”.
And so on.
Basically “hits in the air” only happen when they actually make a difference, which makes sense. If they did otherwise, that would only serve to prolong the battle for no good reason.
For what it’s worth, it could be argued that since the “and run” part of “strike and run” wasn’t carried out, Erlidom didn’t get a full move either.