Eastern, Benoni

In this branch of the Eastern Pterodactyl, White meets 3...c5 neither by capturing on c5 nor by defending d4 but by advancing 4. d5. The pawn gains space and closes the long diagonal in front of the bishop on g7, so the queen sortie and dark-square pressure that drive the Pterodactyl lose much of their force. The result is a Benoni-type structure, with White's pawns on d5 and e4 facing Black's pawn on c5. The engine gives White a slight edge, though results in online play are close to even.

The usual reply by far is 4...d6, which fixes the structure and leaves Black to complete development behind it. Engines also consider 4...a6 and 4...Qb6, the latter hitting b2. Less common choices include 4...Nf6 and 4...e6, which prepares to challenge the d5-pawn. The Pterodactyl-style 4...Qa5 is named the Eastern, Benoni Pterodactyl. Because White's d-pawn has left d2 empty, this queen move pins the knight on c3. White scores somewhat better against 4...Nf6, 4...e6 and 4...Qa5 than against 4...d6.