Austrolejeunea secunda differs from all other species belonging to the Siphonolejeunea generic complex in its acuminate, ventrally secund leaf lobes that have both acroscopic and basiscopic margins reflexed to form a channel extending the entire length of the antical margin, the truncate underleaf lobe apex, the first lobule tooth of three moniliform cells, and the presence of second and third lobule teeth. It is the third New Zealand species of Austrolejeunea from subalpine habitats, and brings to seven the number of Austrolejeunea species known from New Zealand.