Rhenopteroidea

Brachyopterus was one of the earliest known eurypterid genera, having been recovered from Middle Ordovician deposits in Montgomeryshire, Wales. Though other species have been assigned to it in the past, Brachyopterus is today recognized as containing one valid species, B. stubblefieldi.

The Rhenopteroidea is an extinct superfamily of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". The superfamily is one of four superfamilies classified as part of the suborder Stylonurina. Previously considered to consist only of the family Rhenopteridae, the superfamily was in 2025 divided into three families: Rhenopteridae, Brachyopteridae, and Brachyopterellidae.