The early history of Earth covers such vast stretches of time that years, centuries, and even millennia become virtually meaningless. Instead, paleontologists and scientists who study geochronology divide time into periods and eras.

The Silurian Age occurred during the mid-Paleozoic, and despite its relative brevity, the era developed some interesting features that promulgated life on Earth. Roderick J. Murchison, a British geologist, named a sequence of rocks after a group of indigenous people called the Silures living in Wales during the mid-19th century. Despite their absence in the Silurian Age, the name was bestowed to honor the tribe.

Murchison was inspired by close friend Adam Sedgwick, who named the Cambrian Age, employing the Latin word for Wales. In 1835, the two presented a paper together entitled On the Silurian and Cambrian Systems. Their separate categorizing systems caused a serious enough disagreement over chronology that the friendship ended bitterly. The alternative name for Siluria was Gotlandia after the Baltica island of Gotland.

What ultimately precipitated these subdivisions in the chronology was a “famous unconformity” on the River Onny in Shropshire. It indicated a natural break within “classic Silurian on its own home territory.” The timeline for beginning and end dates has remained imprecise, but the order of fossilized discoveries has proven correct. Joachim Barrande, a French paleontologist, geologist, and botanist, pursued the same issue in the Prague Basin of Bohemia. Studying the Paleozoic trilobite for a period of 10 years, his extensive work was published in his Silurian System of Central Bohemia. Altogether, he identified and analyzed over 4,000 new fossil species, producing the enormous Encyclopedia of Fossils, numbering over 6,000 pages.