Bradoriida

Bradoriida; Temporal range: Cambrian stage 3–Mid Ordovician[1] PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Stem group:	Crustacea (?)
Order:	†Bradoriida; Raymond, 1935
Families & Genera
	Beryichonida Beyrichona Matthew, 1886; Parahoulongdongella; ; Compatulida Öpik, 1968 Altuella; Zepaera Jones & McKenzie, 1980; ; Hipponicharionida Sylvester-Bradley, 1961 Albrunnicola (Beyrichona); Hipponicharion; Quadricona Topper, 2010; Meishucunella; Neokunmingella; ; Monasteriida Epactridion; ; Svealutida Öpik, 1968 Liangshanella Huo, 1956; ; Other genera (may fall into above orders or others; please confirm): Albrunnicola; Amphikeropsis; Bradoria; Comptaluta; Dielymella; Haoia; Indiana; Kunmingella; Mongolitubulus(Spinella); Onagrocharion; Shangsiella; Spinospitella; Walcottella; Wimanicharion; ; and others...

Bradoriids are small marine arthropods with a bivalved carapace, and were globally distributed, forming a significant portion of the Cambrian and early Ordovician soft-bodied communities.[1]

Affinity

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.[1]

An in-depth phylogenetic analysis of Panarthropoda included two bradoriid genera, Kunyangella and Kunmingella, and recovered them as the most basal stem-mandibulates.[2]

Occurrence

Bradoriida are geographically widespread, and occur in the fossil record shortly before the earliest trilobite fossils.[1] 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.[1]

References

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.

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[Topper2010-1] 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.

[Siveter2014-2] 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.