My breeding pair (laid eggs, but not raised): Sorry about the crappy pic quality
Male:
Female:
Both the male and female (sorry, can't see it in pics) have the dorsal spike, the male has a much more prominent spike.
The male's dot is muted, with no blue spots in it, the females is brighter, with blue speckles. The male has the black smudge behind the black dot, and the female has one, but much more muted.
The female has a pink tummy, the male does not.
The female's pelvic fin is shorter and blunter than the male's.
Ok, so that doesn't really help out here. I don't think the black smudge is a particularly defining feature; my last male had a black smudge too. I think the dorsal spike (much larger and more prominent on males) is an indicator, as well as the pelvic fin, pink pigmentation and black dot (blue spots or not)