Bile acids are steroid acids found predominantly in the bile of mammals and other vertebrates. These fins evolved into legs of the first tetrapod land vertebrates, amphibians. They are similar to the mesonephros of higher vertebrates (reptiles, birds and mammals). These fins evolved into the legs of the first tetrapod land vertebrates, amphibians. Botulism can occur in many vertebrates and invertebrates. Slugs are preyed upon by myriad vertebrates and invertebrates. The fins evolved into the legs of the first tetrapod land vertebrates, amphibians. Most species feed on invertebrates as juveniles and shift to feeding on vertebrates as adults. The first insectivorous (vertebrates) were amphibians. TLRs are present in vertebrates as well as invertebrates. They are internal parasites of molluscs and vertebrates. These digeneans are themselves parasites in various vertebrates and molluscs. Insects are prey for a variety of organisms, including terrestrial vertebrates. Basal pterosaurs were insectivores or predators on small vertebrates. The first fully terrestrial vertebrates were amniotes.