Temporal range: Cambrian stage 3–Mid Ordovician
|Stem group:||Crustacea (?)|
|Families & Genera|
Whilst the Bradoriida were traditionally considered as relatives of the modern bivalved arthropod group Ostracoda, the anatomy of their appendages does not support such a relationship; neither are they related to the Cambrian bivalved arthropod group Phosphatocopida. Rather, they are most probably related to the Eucrustacea at a stem-group level.
Bradoriida are geographically widespread, and occur in the fossil record shortly before the earliest trilobite fossils. Their taxonomic composition broadly reflects two geographical provinces ("European" and "4A", i.e. America, Asia, Australia, Antarctica) which approximately mirror trilobite provinces, with the 4A area representing warmer waters closer to the palaeoequator.
- Timothy P. Topper; Christian B. Skovsted; Glenn A. Brock & John R. Paterson (2010). "The oldest bivalved arthropods from the early Cambrian of East Gondwana: systematics, biostratigraphy and biogeography". Gondwana Research (in press). doi:10.1016/j.gr.2010.05.012.
- Siveter, Derek J.; Briggs, Derek E. G.; Siveter, David J.; Sutton, Mark D.; Legg, David; Joomun, Sarah (2014). "A Silurian short-great-appendage arthropod". Proceedings of the Royal Society B: Biological Sciences. 281. doi:10.1098/rpsb.2013.2986.