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Hurdia victoria
Hurdia #1
Hurdia is a genus of an anomalocaridids (family Hurdiidae, order Radiodonta) of the Middle Cambrian. The body size of Hurdia is up to 20 cm, the maximum body size will be up to 50cm 1). The genus "Hurdia" is derived from Mount Hurd in Yoho National Park of Canada, and perhaps the species name "victoris" also is named after Mount Victoria in the park 1).
Hurdia #2
The anterior half of Hurdia has coverd with two different types of three carapaces, namely, one is dorsal H-element and two are lateral P-elements 1). H-element is a triangular shape, and P-element is a subrectangular or trapezoidal shape.
A pair of oval eyes is on the tips of short stalks which project from dorso-lateral gaps in the overlapping carapaces 1).
Hurdia #3
Radial array of small plates surround a mouth on the ventral surface of head and shape a square opening. There are some rows of tooth within the mouth. A pair of nine segmented appendages with long ventral spines have protruded from near mouth part 1).
Hurdia #4
The posterior half of the body consists of seven to nine segments. Each segments have "reversely imbricated" lateral lobes 1). Gill-like structures are attached to the anterior margin of the dorsal surface of lateral lobes 1).
Hurdia #5
While Hurdia may have been an active swimmer and preying on other smaller soft bodied animals using its appendages and spiny mouth 1), it may have been a nektonic and a filter-feeder 2). Anyway, the role of carapace remains unknown.
The new study shows that hurdia has both of dorsal and ventral pair of flaps on each trunk segments. The dorsal flaps have setal blades (comb-like structure) which have been seen on other anomalocaridids, and perhaps have a gill function. These dosal and ventral flaps may represent a pre-state of biramous limb evolution. 2).
Hurdia
The anterior half of Hurdia looks like a nib of fountain pen, or a head of squid and the posterior half looks like a shrimp.
created in March 2017.
References:
  1. Royal Ontario Museum. The Burgess Shale, Fossil Gallery
  2. Van Roy P, Daley AC, Briggs DEG (2015) Anomalocaridid trunk limb homology revealed by a giant filter-feeder with paired flaps. [abstract] Nature 522:77–80. (DOI:10.1038/nature14256.)