Thanks to Waypoint User Noble Squash for pointing this out.
If you look at the 2:15 mark in the recent behind the scenes video, towards the bottom left you will see an unidentified creature. This creature looks very similar to a crawler, but is slimmer and much more dog like.
This can also be seen in the E3 trailer, but I didn’t think much of it back then.
Now compare this with the original crawler and the more heavily armored crawler spotted in Spartan Ops.
Heavily Armored Crawler
I believe that the wolf-like promethean is just another class of crawler which varies in its strength and tactics from other crawlers. Perhaps it is the fastest/weakest type of crawler, because instead of having a fully armored pincer head, it has an exposed smaller head. Just a thought, either way I think it looks badass.