The rare starfishes
Myxaster sol were collected during the work of Russian and French expeditions in the north-eastern Atlantic. The data on the variability of characteristics in some specimens (age characters, in particular) and on intraspecific variability showed that
M. sol and
M. medusa were close to each other, whereas
M. perrieri differs in the number of arms, primary radial plates, and the shape of fascicles in primary radial spines.
M. perrieri is suggested to be a synonym of
Pythonaster atlantidis, which also occurs in the northern Atlantic. Based on the morphological analysis of three species of
Myxaster, the importance of species diagnostic characters is reappraised. Some modifications to the diagnose were made.
Myxaster is closely related to the genus
Asthenactis and differs from it in the absence of actinolateral membrane and the number of spines on primary radial and oral plates. In addition, the
Myxaster species differ in the length of adambulacral membrane. The new findings have expanded significantly the
Myxaster range to the north.
