Prehistoric stem group arthropod genera

Anomalocaris (from Ancient Greek , meaning "unlike", and , meaning "shrimp", with the intended meaning "unlike other shrimp") is an extinct genus of radiodont, an order of early-diverging stem-group marine arthropods. It is best known from the type species A. canadensis, found in the Stephen Formation (particularly the Burgess Shale) of British Columbia, Canada. The other named species A. daleyae is known from the somewhat older Emu Bay Shale of Australia. Other unnamed Anomalocaris species are known from China and the United States.

Kylinxia is a genus of extinct arthropod described in 2020. It was described from six specimens discovered in Yu'anshan Formation (Maotianshan Shales) in southern China. The specimens are assigned to one species Kylinxia zhangi. Dated to 518 million years, the fossils falls under the Cambrian period. Announcing the discovery on 4 November 2020 at a press conference, Zeng Han of the Nanjing Institute of Geology and Paleontology, said that the animal "bridges the evolutionary gap from Anomalocaris to true arthropods and forms a key ‘missing link’ in the origin of arthropods," which was "predicte

Lyrarapax is a radiodont genus of the family Amplectobeluidae that lived in the early Cambrian period 518 million years ago. Its fossils were found in the Maotianshan Shales of China. The first species, Lyrarapax unguispinus was described in 2014, with a second species, Lyrarapax trilobus being described in 2016, differing principally in the morphology of its frontal appendages.

Siberion is an extinct genus of lobopodian from the Sinsk biota of Russia. Its anatomy, including the proboscis-like organ projecting from the face and prominent grasping first pair of appendages, suggests that xenusians like this organism may have been phylogenetically related to anomalocaridids, like Anomalocaris. Only two incomplete specimens are known, and the probability of finding more is low, as the Sinsk Algal Lens has been nearly destroyed by commercial fossil collectors.

Erratus is an extinct genus of marine arthropod from the Cambrian of China. Its type and only species is Erratus sperare. Erratus is likely one of the most basal known arthropods, and its discovery has helped scientists understand the early evolution of arthropod trunk appendages. Some of the stem-arthropods like radiodonts did not have legs, instead they had flap like appendages that helped them swim. Erratus on the other hand had not only flaps but also a set of primitive legs. It also supported the theory that the gills of aquatic arthropods probably evolved into the wings and lungs of terr

Megadictyon is a genus of Cambrian lobopodian with similarities to Jianshanopodia and Siberion. The name of the genus is occasionally mis-spelt as Magadictyon.

Paranomalocaris is a genus of radiodont recovered from the Cambrian Stage 4 aged Wulongqing Formation, eastern Yunnan. It contains two species, Paranomalocaris multisegmentalis and P. simplex. It is only known from its frontal appendage.

Jianshanopodia is a monotypic genus of Cambrian lobopodian, discovered in the Maotianshan Shales of Yunnan, China.

Lenisicaris, from Latin lēnis, meaning "smooth", and Ancient Greek καρίς (karís), meaning "shrimp", is an extinct Cambrian anomalocaridid radiodont, known from the Maotianshan Shales of China and the Kinzers Formation of Pennsylvania.

Parvibellus is an extinct genus of panarthropod animal known from the Cambrian of China. It is known from only a single species, P. atavus, found in the Cambrian Stage 3 aged Chengjiang Biota of Yunnan, China.