The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
If larger than an inch - Horseshoe Crab :)
WOW Mark, those are cool-looking creatures!
What was mother nature up to with this one?! Wow! It looks as if it has been pressed in a book.
What family is this bug in? With those operculate gill covers?
It doesn't look like the bug in the link you provided. Your photos seem to indicate a short, squat bug body. The one in the link is long and skinny.
Is it a sulfur?