Who introduced the term Dinosauria and what does it mean?

This is a word composed of two roots of Greek origin, the first (deinós), means "terrible" and the second (sauros), means lizard, so dinosaur means literally "giant lizard". This term was invented in 1841 by Sir Richard Owen and was presented during an annual meeting of the British Association for the Progress of Science. The Dinosauria group originally grouped the three only known dinosaurs: Megalosaurus, Iguanodon and Hylaeosaurus, all from England.

Explanation:

The studies carried out by Richard Owen are so many and so extensive that they are practically unmentionable, however, if we speak of the term dinosaur, the work History of British Fossil Reptiles (History of British reptile fossils), dated 1849.

In this work Richard Owen talks about the large group of reptiles that exercised total hegemony during the Mesozoic Era and named this group with the term Dinosauria, referring to the biological branching of these prehistoric animals.

The term "dinosaur" and "dinosauria" is mainly because Richard Owen studied three fossils that could not be identified with any other fossil or living animal, such was his astonishment that he decided to name these fossil remains as "terrible lizards."