Hibbertopterus is a genus of eurypterid, a group of extinct aquatic arthropods. Fossils of Hibbertopterus have been discovered in deposits ranging from the Devonian period in Belgium, Scotland and the United States to the Carboniferous period in Scotland, Ireland, the Czech Republic and South Africa. The type species, H. scouleri, was first named as a species of the significantly different Eurypterus by Samuel Hibbert in 1836. The generic name Hibbertopterus, coined more than a century later, combines his name and the Greek word πτερόν (pteron) meaning "wing".
Image: Eurypterus scouleri MNHN 1872 19 2
Image: Eurypterus scouleri MNHN 1872 19
Restoration of H. scouleri
Outdated 1872 reconstruction by Henry Woodward of H. scouleri with a telson and appendages based on those of Eurypterus (with swimming paddles and unspecialised walking appendages).
Eurypterids, often informally called sea scorpions, are a group of extinct arthropods that form the order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period 467.3 million years ago. The group is likely to have appeared first either during the Early Ordovician or Late Cambrian period. With approximately 250 species, the Eurypterida is the most diverse Paleozoic chelicerate order. Following their appearance during the Ordovician, eurypterids became major components of marine faunas during the Silurian, from which the majority of eurypterid species have been described. The Silurian genus Eurypterus accounts for more than 90% of all known eurypterid specimens. Though the group continued to diversify during the subsequent Devonian period, the eurypterids were heavily affected by the Late Devonian extinction event. They declined in numbers and diversity until becoming extinct during the Permian–Triassic extinction event 251.9 million years ago.
Eurypterid
Illustration of Hibbertopterus, a large stylonurine (lacking swimming paddles) eurypterid
The holotype of Palmichnium kosinkiorum, containing the largest eurypterid footprints known
The supposed "gill tracts" of eurypterids have been compared to the air-breathing pseudotracheae present in the posterior legs of modern isopods, such as Oniscus (pictured).