Hibbertopteridae

Hibbertopteridae (the name deriving from the type genus Hibbertopterus, meaning "Hibbert's wing") is a family of eurypterids, an extinct group of aquatic arthropods. They were members of the superfamily Mycteropoidea. Hibbertopterids were large, broad and heavy animals unlike virtually every other group of eurypterids, which are commonly streamlined and lightweight. Their bizarre morphology is so unusual that they in the past have been thought to represent an entirely distinct order of chelicerates. Fossils of the family first appear in deposits of Middle Devonian age and the last known fossils representing hibbertopterids are known from deposits of Late Permian age. The hibbertopterids represent the last known living eurypterids, going extinct during the Permian–Triassic extinction event or shortly before.

Although eurypterids are commonly known as "sea scorpions", hibbertopterids inhabited freshwater swamps and rivers and were unable to swim since they lacked swimming paddles, a feature they shared with their entire suborder, the Stylonurina. Hibbertopterids fed using a method referred to as sweep-feeding, in which the animal would rake through the soft sediment of their substrate with specialised blades on their forward-facing appendages to capture small invertebrates. Though this method of feeding was present in other mycteropoids and in stylonuroids, it was at its most advanced stage within the derived Hibbertopteridae.