Prior to the emergence of paleontology and comparative anatomy as scientific disciplines at the end of the 18th century, it was generally known that there were species of animals that had disappeared completely. The term "extinction" originally applied to the extinguishing of fires or erasing of one's debt. It was not until 1784 that the term extinction was used to denote the complete eradication of a species of living being. In 1901, Frederic A. Lucas penned an overview of vertebrate animals whose only evidence of being remained in fossil records. The book focuses primarily on vertebrate animals, from fish to mammals. - Summary by Jeffery Smith