Does Master of the Veil work on Megamorphs?
Master of the Veil is able to turn Stratus Dancer facedown.

Rule 702.36b defines Megamorph as a morph variant, and so Master of the Veil's oracle'd ability can target a face up Stratus Dancer.



Oracle text:


  When Master of the Veil is turned face up, you may turn target creature with a morph ability face down.   


702.36. Morph:


  702.36a Morph is a static ability that functions in any zone from which you could play the card it’s on, and the morph effect works any time the card is face down. “Morph [cost]” means “You may cast this card as a 2/2 face-down creature with no text, no name, no subtypes, and no mana cost by paying {3} rather than paying its mana cost.” (See rule 707, “Face-Down Spells and Permanents.”)
  702.36b Megamorph is a variant of the morph ability. “Megamorph [cost]” means “You may cast this card as a 2/2 face-down creature with no text, no name, no subtypes, and no mana cost by paying {3} rather than paying its mana cost” and “As this permanent is turned face up, put a +1/+1 counter on it if its megamorph cost was paid to turn it face up.” A megamorph cost is a morph cost.