This genus is characterized from other lobopodians due to multiple groups of four nodes running along its trunk region, similar to Kerygmachela, and a pair of extremely large frontal appendages that were possibly as long as the animal's entire body.

[1] The first specimens of Hadranax were first discovered at the base of the larger Buen Formation, more specifically in areas of J.P. Koch Fjord in Northern Greenland.

[1] This genus was very large compared to other lobopodians, with the largest known specimen reaching a length of around 69 millimeters (6.9 centimeters) long (excluding the terminal ends).

[1][3] During the lower Cambrian, the area that would become the Sirius Passet site sat under several hundred meters of water in either the mesopelagic, or bathypelagic zones.

Unlike Hadranax, these two genera possess large lateral flaps on their trunk region, and were swimming in the water column.