The Dog Vomit Fungus (Fuligo septica) is not a fungus, and is certainly not vomit, be it dog or other. It is a myxomycete, a type of slime mould that will feed on microbial communities on rotting vegetation. F. septica grows vegetatively as a mass of plasmodium which moves by amoeboid locomotion and feeding is achieved by phagocytosis (1). Historical references to F. septica as a fungus arose due to its fungus-like habit if producing fruiting bodies under unfavourable conditions. While these can be quite ornate in some species, F. septica produces a simple aethalium, a large, spore containing sack.
Chapman et al., 1982. Experimental Mycology 6 195-199