Hadranax

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Hadranax is a large lobopodian from the lower Cambrian Sirius Passet fossil site in northern Greenland. It is known from about three fragmentary fossils, including the holotype MGUH 24.527. Hadranax stands out for four-node groups along its trunk and extremely large frontal appendages that may have been as long as the animal itself. The largest known specimen is about 6.9 cm long, and Budd & Peel suggested it could reach 15–16 cm when including the end parts. The trunk is about 1.1 cm wide and carries many limb pairs—around twenty in total—with each limb about 1.7 cm long and lacking claws. The frontal appendages are annulated with soft spines.

The Sirius Passet environment was a low-oxygen sea area, which helped preserve these fossils. Hadranax likely lived on the seafloor as a dominant predator, unlike some other lobopodians like Kerygmachela and Pambdelurion, which had large lateral flaps and swam in the water column. The genus name comes from Greek words meaning “sturdy ruler,” and the species name augustus refers to the month when the best specimen was found, in August.