This is the Brutalisk, a campaign-only unit.
This was posted on the official SC Twitter.

Isn't it too arcade?

Whoa! Now, THAT'S a boss.

It needs way bigger legs, it looks ridiculous and like it would fall over immediately, the upper body is pretty awesome though.

Just give it crazy huge spider legs with the usual claw tip and it should be good, or a longer lower body.

Of course Blizzard may never read this...

Ahahahaha it does kind of look like it needs bigger legs...

Well, insectoids are often very strong if you compare their strength to their body weight.

Just look at ants, for instance. So although it does look really weird, it doesn't mean it's silly.

This should be some fun. I Hope they have a lot of boss units in story mode. It makes for interesting play. So far we have seen Giant Zealots with Collosi Beams and then this Queen looking lurker hybrid. Awesome!

Yes insects have ridiculous strength to body weight ratios, but go compare an ant's legs to it's body size, you see it has barely anything that comes over it's knees and it's legs are proportionally quite big.

This thing would collapse or fall over forward if it leaned at all.