What evidence shows that branchiopods existed by the Devonian Period?

Evidence for the existence of branchiopods during the Devonian Period is provided by the presence of two distinct groups: the Lipostraca and the Spinicaudata.1

The most significant evidence comes from the Lipostraca, represented by the species Lepidocaris rhyniensis, which was discovered in the Rhynie cherts of Scotland. This fossil is exceptionally well-preserved, allowing scientists to observe fine details of its limbs, which provides more structural information than is available for any other fossil crustacean. Researchers have even been able to deduce its feeding methods, noting that its first three pairs of trunk limbs were likely used to scrape material from surfaces, while the subsequent limbs were two-branched and used for swimming.1

Additionally, fossil members of the Spinicaudata have been identified from the Devonian period. While these are not as detailed as Lepidocaris—often being preserved only as carapaces—they confirm the presence of the suborder during this time.1