Members of the Leptasterias aequalis species complex are small to medium sized. They have six arms up to 5 cm long, and their arm-to-disc ratio is about 4. To the naked eye, the aboral and lateral surfaces seem to be compactly covered with clusters of granular spines (up to 10) with small papular areas separating them. These sea stars have a carinal series of tightly spaced clusters of spines and a dorsolateral series of one to six spinelets per cluster in well-defined longitudinal rows; their pedicellariae are usually present but inconspicuous; the aboral spines are typically subcapitate; the superomarginals each have 4 to 8 slightly bent spines in a vertical series; the inferomarginals have two longer spines; and the oral intermediates are arranged in one, occasionally two, well-developed series. The adambulacrals have one or two spines in irregular alternation. There are clusters of crossed pedicellariae on the distal sides of the adambulacrals, oral intermediates and inframarginals.
Similar SpeciesSmall Leptasterias may be confused with juveniles of Pisaster ochraceus or Evasterias troschelii, which occasionally have six arms. P. ochraceus has a single spine on each adambulacral, with a cluster of pedicellariae at the base but not on the spine. Leptasterias has one or two spines per plate with a cluster of pedicellariae on the spine itself. E. troschelii has pedicellariae on the adambulacrals but an arm-to-disc ratio of 5.0-7.6 and six similar rows of spines between the superomarginals and the furrow, made up of two inferomarginals and four oral intermediates. Leptasterias has no more than two oral intermediates.