Quick Answer. When a solid turns into a liquid it is called fusion, more commonly referred to as melting. When a material moves from one state of matter into another it is called a phase transition. Fusion is just one of approximately different states that matter can phase through.
Before the dinosaurs, there were Triops. Fossil Triops more than 200 million years old have been discovered. By comparison, dinosaurs date back only about 60 million years...just 'youngsters' in terms of geologic time. Triops are distant relatives of trilobites. Triops means three-eyes while the name trilobite means three lobed or three segments.
The non-mammalian members are described as mammal-like reptiles in classical systematics; they can also be called stem mammals or proto-mammals. Synapsids evolved from basal amniotes and are one of the two major groups of the later amniotes; the other is the sauropsids, a group that includes modern reptiles and birds. The distinctive temporal fenestra developed in the ancestral synapsid about 312 million years ago, during the Late Carboniferous period. Synapsids were the largest terrestrial vertebrates in the Permian period, 299 to 251 million years ago, although some of the larger pareiasaurs at the end of Permian could match them in size.