Stampeding Horncrest

The haste clause is doing all the pricing here, and the body is deliberately undersold so the reward can track how far you committed. Cast this into a board already holding another Dinosaur and you get an immediate clock, a threat that swings the turn it lands instead of telegraphing itself a full turn out. Cast it with no other lizard around and you have overpaid for a wall that sits until your next untap. That gap is the design being honest with you: it never fakes up a body good enough to run outside the tribe, so the incentive is legible and the tax is mild. The window it manipulates is the summoning-sickness gap, and it only closes that gap once the deck is already built around it, which makes it genuinely worse in a shell splashing one or two Dinosaurs and genuinely good in one running a dozen. Haste that scales with board presence is a well-worn lever, but anchoring it to a creature type rather than an engine keeps the payoff cheap to print: no counting mana, no tracking a resource, just a glance at the board to see whether another Dinosaur is standing. What you get is a tribal payoff that asks you to count before committing, and shrugs when the count comes up short.