Described by Chamberlin (1917: 36).
Like Aptostichus stephencolberti and Aptostichus miwok, Aptostichus simus is distributed throughout the California coastal dune habitats. Specimens are known from Baja California Norte, northward along beaches in San Diego, Orange, Los Angeles, Ventura, Santa Barbara, and San Luis Obispo Counties; their distribution ends just north of Point Conception with two disjunct populations in Monterey County and on the Channel Islands just off the California coast (Map 32). Like other coastal dune species, Aptostichus simus is found in relatively deep burrows on the steep faces of sand dunes and at the base of coastal vegetation. Burrows comprise a thick silk lining and are covered by a very cryptic trapdoor constructed of silk and sand. Dune habitats disturbed by high concentrations of the invasive Carpobrotus edulis (ice plant) tend to lack Aptostichus simus.