We are referring to Postosuchus the nightmare from the late Triassic, some 220 million years ago.
Postosuchus was an ugly looking customer; on all fours it looked a bit like a really nasty crocodile but on four long legs, standing and running upright like a dog or cat, very unusual for a reptile. It's rear legs were also about 35% longer than the front, so most scientists believe it reared back and did a T-rex imitation from time to time, probably to amuse the kids. Of course, T-rex, had he been present would have had Post-O for lunch, being many times its size.
Postosuchus was neither dinosaur nor crocodile, but an archosaur of the Rauisuchian line which essentially means that it was a proto-dinosaur of the same lineage that spawned crocodiles, birds and dinosaurs.
15' long, 6.5 tall on all fours and significantly taller in bi-ped mode, Posty averaged about 700 lbs. A really big one might go 20' and tip the scales a 1000 lbs.
Postosuchus was a lot like today's Federal Government, rapaciously consuming everything it could get its teeth into. One notorious specimen was found with no less than three medium sized contemporary critters in its gut, leading one to suspect it died of indigestion.
Had there been Tums 200 million years ago, Postosuchus might be with us today. Of course, cryptozoologists don't rule out the survival of anything so just be careful when you answer the door bell, and count the number of rings. (The postosuchus always rings twice.)
If you want to know more about this singularly unattractive creature, there are two mildly relevant articles HERE and HERE.
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