Panlongia was a small-sized (up to 2 cm) marine arthropod, with an oval-shaped non-calcified exoskeleton. Both the head shield (or cephalon) and the tail shield (or pygidium) are semi-circular. In between the cephalon and pygidium are four thoracic body segments (somites). The cephalon occupies approximately ⅓ of the body length, the thorax ¼ and pygidium about 45%. Panlongia lived during the late Lower Cambrian (Botomian) in what is today South China. In Panlongia spinosa the edge of the exoskeleton carries several small sawtooth-like spines, that are absent in P. tetranodusa.[1]
The phylogenetic position of Panlongia remains uncertain, because the appendages remain unknown sofar. Panlongia cannot yet with confidence be assigned to the Helmetiida or the Nektaspida,[2] as was initially suggested.[1]
Panlongia tetranodusa occurs with the coeloscleritophoran Allonia sp., the vetulicolian Vetulicola gangtoucunensis, lingulate brachiopods Lingulellotreta malongensis, Diandongia pista, Acrothele rara, and Westonia gubaiensis; dinocaridid Houcaris saron, hyolith Linevitus malongensis, eocrinoid Wudingeocrinus rarus, Trilobites Redlichia yunnanensis, R. mansuyi, R. noetlingi, R. conica, R. shijiangjunensis, Palaeolenus douvillei, and P. lantenoisi; crustaceans: Tuzoia sinensis, T. tylodesa, Branchiocaris sp., Liangshanella liangshanensis, and Neokunmingella sp., and several other arthropods like Longquania bispinosa, Guangweicaris spinatus; Leanchoilia illecebrosa, Isoxys minor, I. wudingensis and Gangtoucunia aspera.[1]