cheirurids

Cheirurids were a diverse and widespread group of extinct trilobites that lived during the Paleozoic Era, from the Early Ordovician to the Late Devonian periods. Their taxonomic classification places them within the order Cheirurida. These trilobites are characterized by several distinctive features, most notably their highly effaced (smooth) cephalon (head shield) and glabella (central lobe of the cephalon). A common trait among cheirurids is the presence of genal spines, which are extensions of the genal angles (corners of the cephalon), and often a pygidium (tail shield) with prominent spines. The pygidium of cheirurids is typically semicircular to triangular in shape and displays a characteristic segmentation.

The family Cheiruridae is the most prominent within the order, but other families like Encrinuridae and Deiphiniidae also exhibit cheirurid affinities. Cheirurids inhabited a variety of marine environments, from shallow continental shelves to deeper waters. Their fossils are found globally, indicating their broad distribution across the ancient oceans. The ecological role of cheirurids is thought to have varied, with some likely being detritivores or scavengers, while others may have been predators. Their robust exoskeletons and the presence of genal spines suggest they possessed defensive capabilities against predation. The study of cheirurids provides valuable insights into trilobite evolution and Paleozoic marine ecosystems.