This phyllocarid arthropod is known as Branchiocaris
pretiosa, and has a long legacy since the description of the
genus from a Burgess
Shale specimen by Resser in 1929. The affinity
of Branchiocaris is disputed. Some rank it as being
within a stem group of
euarthropods, and others as a primitive branchiopod crustacean
within the arthropod crown
latter being the most accepted classification.
had a large carapace that protected the anterior body parts.
Its carapace structure hinged along the dorsal
edge in the same manner as seen in bivalves. Usually only the carapace
is found fossilized, and only very rarely are the soft parts
preserved in as in this case in lagerstatte fossil sites such
as the Wheeler Formation. That said, such soft-tissue preservation
is rare in the formation.
the Burgess Shale of British Columbia,
where it is also rare (less than .01% of the biota), another
member of the genus (Branchiocaris yunnanensishas) is described
from the Chengjiang
(1929) named the genus Protocaris and classified it as a phyllocarid
crustacean, but other workers later considered
more closely related to trilobites. Four decades later Briggs (1976)
erected the new genus Branchiocaris, prefering a stem arthropod
(1997) later placed Branchiocaris was a calmanostracan branchiopod,
while other's phylogenetic analyses placed it close to Marrella
(Briggs, Fortey and Wills, 1992). Budd (2008) argued Branchiocaris
a stem euarthropod, belonging to a clade also containing
Perspicaris and Canadaspis.
Thus, Branchiocaris continues its enigmatic legacy.
subclass Phyllocarida contains three orders, one extant (Leptostraca,
classified as a Malacostracan), and two extinct
(Hymenostraca and Archaeostraca).
See: Utah Cambrian Explosion
DE. 1976. The arthropod Branchiocaris n. gen. Middle Cambrian,
Burgess Shale, British Columbia. Geological Survey of Canada
Bulletin, 264: 1-29.
DE. Fortey, MA., and Wills, MA. 1992.
Morphological disparity in the Cambrian. Science, 256: 1670-3.
Chen, J., Waloszek, D. & Maas, A. 2004 A new ‘great-appendage’ arthropod
from the Lower Cambrian of China and homology of the chelicerate
chelicerae and raptorial antero-ventral appendages. Lethaia 37, 3–20.
D.E., Lieberman, B., Hendricks, JR., Halgedahl, SL., & Jarrard,
RD. 2008. Middle Cambrian arthropods from Utah. Journal of Paleontology,
GE. 2002. A palaeontological solution to the arthropod head
problem. Nature, 417: 271-275
GE. 2008. Head structures in upper stem-group euarthropods. Palaeontology,