Aptostichus atomarius Simon 1891

Aptostichus atomarius, the San Bernardino hills trapdoor spider, is a species of wafer-lid trapdoor spider in the family Euctenizidae. It is found in the United States.

Aptostichus atomarius es una especie de araña migalomorfa del género Aptostichus, familia Euctenizidae.​ Fue descrita científicamente por Simon en 1891.​

Habita en los Estados Unidos.​ Se encuentra en los condados de San Diego, Riverside, Orange, San Bernardino, Los Ángeles, Ventura, Santa Bárbara, San Luis Obispo, Tulare e Inyo.

Aptostichus atomarius est une espèce d'araignées mygalomorphes de la famille des Euctenizidae.

Aptostichus atomarius là một loài nhện trong họ Cyrtaucheniidae. Loài này phân bố ở Hoa Kỳ.

Female originally described by Simon (1891); Male described and female redescribed by Bond and Opell (2002).

Aptostichus atomarius is widely distributed throughout southern California and has been collected in San Diego, Orange, Riverside, San Bernardino, Inyo, Los Angeles, Ventura, and San Luis Obispo counties (Map 2). Populations to the south are found throughout the Peninsular Ranges including the San Ysidro and Jamul Mountains, bounded to the east by the Laguna Mountain range. Moving northward in the Peninsular Ranges populations are abundant in the San Jacinto and Santa Ana Mountains. Like species described for the closely related genus Apomastus Bond and Opell 2002, Aptostichus atomarius was probably once more extensively distributed across the Los Angeles Basin but is now restricted to the steep ravines of the surrounding San Gabriel and Santa Monica Mountains and the Palos Verdes Hills along the coast. Populations to the north are distributed throughout the northeast extent of the Transverse Ranges bounded by the San Bernardino Mountains but extending northward along the coast in the Santa Ynez Mountains into the southernmost extent of the Coastal Ranges. A couple of morphologically similar specimens, collected from Tulare County in the southern extent of the Sierra Nevada Mountain range, are considered herein to be Aptostichus atomarius but will likely be removed to a separate species at a later date. From a geographical perspective it would seem reasonable to include these specimens in the Aptostichus dantrippi hypothesis, however, Aptostichus dantrippi individuals are distinctive morphologically and are considered a separate cohesion species at this time. Future molecular studies will likely resolve the placement of these outlier populations but until such data are available they are retained here as Aptostichus atomarius on the basis of their morphological affinity with all other specimens. Finally, a number of additional allopatric populations are found out on the Channel Islands and have likely been separated for a considerable amount of time but are likewise retained herein as Aptostichus atomarius until additional character systems can be employed to resolve their placement (or allocation to a new species). The DM produced for this species (Map 3) shows the areas with the highest probability of predicted occurrence to be in the Peninsular and southernmost extent of the Transverse Ranges (around the Los Angeles Basin). Many of the populations in the desert to the east and the Coastal and Sierra Nevada Ranges to the north fall in areas predicted to have a very low probability of occurrence in the model, likely reflecting the fact that this species delineation comprises > 1 species. In the Peninsular, Transverse, and Coastal Ranges, Aptostichus atomarius is restricted primarily to the California Coastal Range Open Woodland-Shrub-Coniferous and California Coastal Chaparral Forest and Shrub ecoregions. Vegetation types comprise mainly mixed chaparral, chamise-redshank chaparral, and coastal scrub. Male dispersal times are widely varied across specimens examined as part of this study. However, the majority of males were collected during the late fall to winter months of October through to March. Occasionally specimens have been collected during the summer months of June and August but these represent very rare occurrences. Females construct burrows that are typical for members of the genus.