Illustrations of Ordovician conodont and Sacabambaspis

Illustrations of Ordovician, jawless vertebrates. Left is a Promissum conodont, ranging from 5 to 50 cm in length and named after unusual, cone-like teeth fossils, which are hypothesized to be ancestors of modern lampreys and hagfishes. On the right is a pair of Sacabambaspis, around 35 cm in length, which had distinct, forward-facing eyes and an armored head. Very few conodont species survived the Late Ordovician Extinction Event, and no fossils of animals like Sacabambaspis from after the event have been discovered.