Sicilian, Siroccopteryx

The Siroccopteryx arises from the Eastern move order of the Pterodactyl Defense. After 1. e4 g6 2. d4 Bg7 3. Nc3 c5 4. Nf3 Qa5, White ignores the tension in the center and continues development with 5. Bc4, aiming the bishop at f7 and preparing to castle. The drawback is that d4 is attacked by the c-pawn and the bishop on g7, while the knight on c3 is pinned against the king by the queen on a5 because d2 is empty. White's ability to hold the center is therefore limited. Engines regard the position as a large advantage for Black.

By far the most common reply is 5...cxd4, chosen in about two-thirds of games. It removes White's d-pawn and leaves White to deal with the opened long diagonal and the pin on c3. In online play Black scores very heavily with it. The developing moves 5...Nf6 and 5...Nc6 are the next most frequent choices, and both are favored by the engine, but in practice they produce more balanced results than the immediate capture. Slower tries such as 5...e6 and 5...d6 give White time to consolidate, and White scores well against them. The line is seen mainly at club and online level, where 5. Bc4 is a natural-looking move that misjudges the position.