I was asked on Facebook what the story behind this was. I was a little surprised at my answer. Here it is:
What if a creature evolved with a supine posture? I'm not aware this has happened in our animal kingdom, but it could. Think of a biped or upright creature that has since further evolved toward the stability of the supine (belly-up) posture. In this case, to keep the tail forward as the main sensory organ. I imagine it serves much as an elephant's trunk, passing food to the snout; or perhaps it has a reverse digestive system with waste passing out through the "snout." Either way, there are aquatic elements that suggest that it dwells within a fluid, at least part of the time. Those "ribs" on the chest look like fluid intakes/outlets, perhaps an alien type of gill or lung. The similar outlets on the spine could be sonic or sonar-related, or they could allow fluid into the nervous system (as coolant?)
I surmise that it leaps like a reverse rabbit, pushing off with its "arms" and landing on its "toes" with the tail fishing all over the ground for food. Probably spends most of the time in shallow water/swamp. The morphology makes sense in terms of a scavenger that needs to keep its head upright and alert for predators. Perhaps the "ribs" are like snorkels in this respect, keeping air intakes above the water line for a shallows-dwelling creature. In hindsight I think his hands should have some half-webbing between the fingers. I'll probably add them. The chest looks like exposed organs, like an open-heart surgery. What probably started as my attempt to add further gross-out elements now has an explanation in my mind: the lungs probably bloat up like a balloon of vibrant color as a mating display, similar to displays seen in frogs, lizards and birds. The hard "ribs" act as armor to protect this vulnerable zone. I imagine the belly has evolved to be very tough leather, almost bone.