The standard for araucana is rumpless and tufted. They are a bantam sized breed, so that is their standard. As for the rumpless and tufted, you can have a pure araucana that has neither, both or only 1 of those characteristics. However, if they are truly bred they can produce offspring that can throw any of the possible characteristics. The tufted gene is lethal in embryo if received from both parents, hatch rates are affected b/c the chicks will make it to pip and even hatch and then die (some die just before pipping), so I understand it is not wise to breed two tufted parents. More on tufts, they can not only have 0 or 2, but can also have just 1 sticking out of one side of their head. Right now I have a rumpless rooster, a duckwing pullet with tail & no tufts and a rumpless blue (light blue) that we're waiting to express its gender.
Are you sure you're new chick has tufts vs a muff? Just curious.
You're chick, however looks rumpless. If its not it will have at least a little nub. The rumpless ones don't even possess the bone structure to support a tail and may get a feather or two (my roo has 2 feathers that hang down from where his rump should be). They are hard to sex b/c roosters typically develop tail feathers very slowly, so unless it has a well colored comb at a young age they can be hard to sex until they get all their feathers in and start showing secondary sex characteristics.