The pyroxene pallasite grouplet is a subdivision of the pallasite meteorites (stony-irons).
[1] The grouplet is named "pyroxene pallasites" because they are the only pallasites that contain pyroxene.
[2] It currently has only two members: the Vermillion and Yamato 8451 meteorite.
Both meteorites contain pyroxene and have a number of other similarities: for example their pyroxene composition, rare-earth element concentrations, and oxygen isotope ratios.
However, there are also indicators against the grouping of these two meteorites: for example the texture and occurrence of cohenite in the Vermillion meteorite and the differing siderophile trace element concentrations.