Magellanic spiral
A Magellanic spiral galaxy is a spiral galaxy with only one spiral arm. Magellanic spiral galaxies are classified as the type Sm ; the prototype galaxy and namesake for Magellanic spirals is the Large Magellanic Cloud, an SBm galaxy. They are usually smaller dwarf galaxies and can be considered to be intermediate between dwarf spiral galaxies and irregular galaxies. They are found in proximity to larger spiral galaxies such as the Milky Way, as is the case with the LMC and the Small Magellanic Cloud.
Magellanic spiral galaxies also have a stratified stellar structure; main sequence stars are found in their spiral arm, and supergiants are clustered in a thick rectangular bar across the middle.
Magellanic spirals
SAm galaxies are a type of unbarred spiral galaxy, while SBm are a type of barred spiral galaxy. SABm are a type of intermediate spiral galaxy.Type Sm and Im galaxies have also been categorized as irregular galaxies with some structure. Sm galaxies are typically disrupted and asymmetric. dSm galaxies are dwarf spiral galaxies or dwarf irregular galaxies, depending on categorization scheme.
The Magellanic spiral classification was introduced by Gerard de Vaucouleurs, along with Magellanic irregular, when he revamped the Hubble classification of galaxies.