Amphibians are a class of cold-blooded vertebrates within the animal kingdom that are distinguished by their life cycle, typically involving a stage as an aquatic larva followed by a terrestrial adult stage. They include various species such as frogs, toads, salamanders, and newts. The term can also extend to unidentified placozoans, which are a phylum of primitive invertebrate animals that consist of simple cellular organization. Despite the difference in complexity, both amphibians and placozoans share the common characteristic of being part of the broader animal kingdom.