Late Ordovician mass extinction in the context of "Trilobite"

The Capitanian mass extinction, also known as the end-Guadalupian, Guadalupian-Lopingian, or pre-Lopingian extinction began around 262 million years ago with its most intense pulse peaking at 259 million years ago, marking the end of the Capitanian stage and Guadalupian (Middle Permian) epoch of the Permian. Historically conflated with the better-known Permian–Triassic extinction, it was only recognised as a distinct event in 1994. Despite this, the mass extinction is believed to be the third-largest of the Phanerozoic in terms of the percentage of genera (33-35%) and species (60-63%) lost after the end-Permian and Late Ordovician mass extinction, while being the fifth worst in terms of ecological severity. The global nature of the Capitanian mass extinction has been called into question by some palaeontologists as a result of some analyses finding it to have affected only low-latitude taxa in the Northern Hemisphere.

The Hirnantian glaciation, also known as the Andean-Saharan glaciation, Early Paleozoic Ice Age (EPIA), the Early Paleozoic Icehouse, the Late Ordovician glaciation, or the end-Ordovician glaciation, occurred during the Paleozoic from approximately 460 Ma to around 420 Ma, during the Late Ordovician and the Silurian period. The major glaciation during this period was formerly thought only to consist of the Hirnantian glaciation itself but has now been recognized as a longer, more gradual event, which began as early as the Darriwilian, and possibly even the Floian. Evidence of this glaciation can be seen in places such as Arabia, North Africa, South Africa, Brazil, Peru, Bolivia, Chile, Argentina, and Wyoming. More evidence derived from isotopic data is that during the Late Ordovician, tropical ocean temperatures were about 5 °C cooler than present day; this would have been a major factor that aided in the glaciation process.

The Late Ordovician glaciation is widely considered to be the leading cause of the Late Ordovician mass extinction, and it is the only glacial episode that appears to have coincided with a major mass extinction of nearly 61% of marine life. Estimates of peak ice sheet volume range from 50 to 250 million cubic kilometres, and its duration from 35 million to less than 1 million years. At its height during the Hirnantian, the ice age is believed to have been significantly more extreme than the Last Glacial Maximum occurring during the terminal Pleistocene. Glaciation of the Northern Hemisphere was minimal because a large amount of the land was in the Southern Hemisphere.