Molecular and morphological analyses of
Patiriella regularis revealed two distinct forms that co-occur widely around New Zealand. Morphotypes are easily diagnosed by plate arrangement along ray crests. Early last century, Mortensen (1925) recorded two varieties that he considered distinct from
P. regularis. Variety "a" corresponds to a form that is not
P. regularis and variety "b" corresponds to juvenile forms of
P. regularis. Mitochondrial DNA data are congruent with morphology, and indicate that the forms are genetically highly distinct from each other (21.1-23.0% sequence divergence) and from other representatives of
Patiriella (17.6-24.5%). Despite their sympatry and morphological similarity, phylogenetic analysis suggests that the two forms represent a paraphyletic assemblage. We therefore describe a new littoral species from New Zealand:
Patiriella mortenseni sp. nov. (Mortensen's variety "a"). Our morphological revision also encompasses similar asterinids recorded from the region:
Asterina novaezelandiae, Patiriella oliveri, and
Patiriella mimica (junior synonym of
P. regularis.