Fianchetto, Rhamphorhynchus

This line of the Pterodactyl Defense comes from the Modern Defense move order 1. e4 g6 2. d4 Bg7. White replies 3. g3 and prepares a kingside fianchetto of their own. After 3...c5 4. dxc5 Qa5+, Black checks and intends to recover the pawn on c5, which is the defining Rhamphorhynchus idea. Until Black regains it, White is a pawn up with doubled c-pawns, and the d4-square is gone, so the g7-bishop has an open long diagonal toward b2.