Flightless Skeleton Goonie
From the Super Mario Wiki
Flightless Skeleton Goonies are enemies that appear in Super Mario World 2: Yoshi's Island, Yoshi's Island: Super Mario Advance 3, Yoshi's Island DS, and Yoshi's New Island. They are simply Skeleton Goonies that do not have wings, similar to Flightless Goonies.
In the levels they appear in, Flightless Skeleton Goonies travel in groups of six, and move extremely fast, much like their living cousins.
Flightless Skeleton Goonies also make a cameo appearance, though not as an enemy, in Super Princess Peach.