Tuzoia

Tuzoia (from Mount Tuzo, a mountain in the Canadian Rockies) is an extinct genus of large bivalved arthropod known from Early to Middle Cambrian marine environments from what is now North America, Australia, China, Europe and Siberia. The large, domed carapace reached lengths of , making them amongst the largest known Cambrian arthropods.

== Description == left|thumb|250x250px|Diagrammatic reconstruction The largest carapaces of Tuzoia are known to reach in length, suggesting a total body length of approximately . Along the sides of the carapace a spiked ridge is present, and the edges and midline of the carapace are also spiked in many species. These spines likely functioned to aid stability while swimming. The carapaces are marked with a reticulate (net-like) pattern, which was likely to increase the structural integrity of the valves while remaining lightweight. The head had a anterior/ocular sclerite at the top, a single pair of large stalked eyes, and a pair of segmented antennae. The head also bore pairs of cephalic appendages, which have curved setae. The first two limb pairs, dubbed the "cephalothoracic legs" have 7 podomeres (segments), with spinose endites (structures that project downwards from the limbs), with the legs ending in a terminal claw. The basipods (basalmost segments of the limbs closest to the body) are greatly elongated, and bears 5 to 6 endites, which become spinose at their ends. It is unclear whether exopods (the upper branch of a two branched (biramous) limb) are present on these limbs. There are likely 10 pairs of trunk legs excluding the cephalothoracic legs. These had seven podomeres, the first with a spinose endite, with the limb ending in a terminal claw, and a similarly elongated basipod, which had a spine proximal to that of the first podomere. These limbs likely had paddle-shaped exopods. The body terminates with a large tail fan.