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Species Coriarachne brunneipes

black crab spider - Bassaniana, perhaps Utahensis? - Coriarachne brunneipes crab spider on door - Coriarachne brunneipes black crab spider - Coriarachne brunneipes - male A Bark Crab Spider? - Coriarachne brunneipes black crab spider - Coriarachne brunneipes - male Crab spider - Coriarachne brunneipes - female Coriarachne? - Coriarachne brunneipes - male Bark spider? - Coriarachne brunneipes
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Chelicerata (Chelicerates)
Class Arachnida (Arachnids)
Order Araneae (Spiders)
Infraorder Araneomorphae (True Spiders)
No Taxon (Entelegynae)
Family Thomisidae (Crab Spiders)
Genus Coriarachne
Species brunneipes (Coriarachne brunneipes)
Easily distinguished from the other species by its relatively uniform color and flat carapace. (1)

Where Coriarachne and Bassaniana are both found they can be identified by the hairs on the carapace. See Rod Crawfords comment; "This is either Coriarachne brunneipes or Bassaniana utahensis. The key feature is whether the large setae on the carapace have pointed ends (Coriarachne) or blunt ends (Bassaniana)."

So I looked at these carefully today, comparing only the males of spiders I think the ID is 100% correct.

Here is what I see... for differences.
Coriarachne brunneipes males tend to have a
1. more elongated abdomen
2. less coloring on the legs
3. longer leg segments
4. carapace tends to have deeper 'grooves'
5. Perhaps the white marking on the abdomen tend to point more forward toward the edges.

Now I think there is the possibility that many of the Coriarachne brunneipes photographed were just 'thinner' than the Bassaniana utahensis, but up to now those points seem to be consistent.
Western United States from Rocky Mountains to Pacific coast, in Canada from British Columbia eastward to northern Ontario. (1)
Internet References
(1) American Arachnology - A Taxonomic Revision of the Crab Spider Genus Coriarachne for North America North of Mexico.