See text Hurdiidae (synonymous with the previously named Peytoiidae[1]) is an extinct cosmopolitan family of radiodonts, a group of stem-group arthropods, which lived during the Paleozoic Era.

Hurdiidae is characterized by frontal appendages with distal region composed of 5 subequal blade-like endites, alongside the enlarged head carapaces and tetraradial mouthpart (oral cone).

[6] The majority of hurdiids appear to have been predators that fed by sifting sediment with their frontal appendages, but some members, like Aegirocassis, Pseudoangustidontus, and possibly Cambroraster were suspension feeders.

[4] The earliest known hurdiid in the fossil record is Peytoia infercambriensis, which lived during the third age of the Cambrian in what is now the country of Poland.

Hurdiidae is defined phylogenetically as the most inclusive clade containing Hurdia victoria but not Amplectobelua symbrachiata, Anomalocaris canadensis, or Tamisiocaris borealis.