Fritillary folly?

Sometimes I wonder why I venture into ID's that are way over my head.  Well, I don't mind making a fool of myself and I have to learn somehow, right?

With that in mind, I turn to a fritillary I photographed in the Black Hills of South Dakota last weekend.  Here are just a couple quick pictures:

Ok, I may as well start with just a list of "greater" fritillaries that my two books (I'm a beginner, remember?) show as occurring in western South Dakota.  I get:

Great Spangled Fritillary

Regal Fritillary

Coronis Fritillary

Aphrodite Fritillary

Atlantis Fritillary

Edward's Fritillary

Callippe Fritillary

Let's look at the eye color of our mystery butterfly:

If I dare to make the point that the eyes are NOT dull yellow-green, that excludes both Great Spangled and Aphrodite Fritillaries.  For example, here is a Great Spangled from Iowa:

That leaves us with:

Regal Fritillary

Coronis Fritillary

Atlantis Fritillary

Edward's Fritillary

Callippe Fritillary

For a lot of obvious reasons (I think), it's safe to say that this isn't a Regal Fritillary.  Namely the lack of a dark HW and darker black margins on the FW above.  Here is a Regal from Iowa for comparison :

Now we're stuck with:

Coronis Fritillary

Atlantis Fritillary

Edward's Fritillary

Callippe Fritillary

As you can see from the following picture, our mystery butterfly doesn't have a "strong green reflection" on the underside of the hindwing.  This should exclude Callippe; the population in Colorado has green HW disks whereas the more western populations get tougher.  The lack of this "green reflection" on the underside especially excludes Edwards':

Further narrowing down our possibilities, we're left with:

Coronis Fritillary

Atlantis Fritillary

I guess this is officially where I get very lost.  I'm not sure, but from what I can tell, Atlantis Fritillary is supposed to have fairly heavy black markings on the upperwing, including thicker hindwing margins and thicker, "swollen" wing veins.  I don't see this on our mystery fritillary:  

       

I also think the HW marginal spots are more rounded than tent-shaped, another point towards Coronis: 

Lastly, a couple other minor things make me lean towards Coronis as well.  First, Coronis is said to have a flight season of late-May through early-September.  Contrastingly, Atlantis is said to be "mostly" around in July (although there is a lot of slop to that).  Lastly, most range maps just put a dot in the Black Hills for Atlantis Fritillary whereas Coronis is shown to be more widely distributed in that part of the state.

Lastly, any thoughts?  I'd be very pleased if someone who knows these fritillaries better to correct me if I'm wrong.