Cynodonts are a group of extinct animals that are known for their advanced mammalian characteristics. They were the first animals to have differentiated teeth and a single temporal opening in the skull. Synonyms for cynodont include mammal-like reptile, therapsid, mammal-like animal, and synapsid. These terms are used depending on the level of emphasis on their mammalian or reptilian characteristics. Scientists have studied the evolution of cynodonts extensively, as they belong to a crucial period in Earth's history when mammalian characteristics began to develop in reptilian ancestors. Cynodonts played a key role in the evolution of mammals and our understanding of the history of life on Earth.