Radiodonts, enigmatic stem-group euarthropods and some of the earliest apex predators, are iconic animals of the Cambrian Explosion.

As one of the two main lineages of radiodonts, the hurdiids are characterized by a tripartite cephalic carapace composed of a dorsal central element and paired lateral elements, a pair of frontal appendages bearing elongate blade-shaped endites and a tetraradial oral cone.  

Although the Hurdiidae has a cosmopolitan distribution in the Cambrian, their Miaolingian occurrences are restricted to Laurentia and the knowledge of their diversity during this time has potentially been biased and incomplete. 

Recently, Prof. ZHAO Fangchen, postgraduate SUN Zhixin and Dr. ZENG Han from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) descovered two hurdiid genera from the middle Cambrian in Shandong Province, which was the first discovery of hurdiid radiodonts in North China.

Relevant results were published in Palaeogeography, Palaeoclimatology, Palaeoecology and Journal of Paleontology. 

Cordaticaris striatus gen. et sp. nov. was collected from the middle Cambrian (Miaolingian, Drumian) Zhangxia Formation in Linyi City, Shandong Province. This new taxon is characterized by a heart-shaped central element with linear ornament, frontal appendages equipped with nine blade-like endites including seven subequal elongate endites, a node-bearing 'peytoia'-type oral cone, and a trunk covered with rows of setal structures.

Cordaticaris not only enriches the taxonomic diversity of Hurdiidae, but also further exhibits the great morphological disparity of hurdiids. The discovery also stresses the great potential of the Miaolingian strata of North China for the preservation of non-biomineralized organisms. 

Cambroraster, first discovered from the Burgess Shale in 2019, is readily distinguishable from other hurdiid taxa by its central head sclerite with deep posterior notches, a rounded anterior margin, and posterolateral processes bearing multiple spines.

New specimens of Cambroraster were found from the Upper Shale Member of the Mantou Formation (uppermost Wuliuan) in Weifang City, Shandong Province. This discovery suggests that Cambroraster had dispersed over a wide biogeographic range, and indicates that the Upper Shale Member of the Mantou Formation is a promising Burgess Shale-type Lagerst？tte. 

The research was supported by the Strategic Priority Research Program (B) of Chinese Academy of Sciences, National Natural Science Foundation of China, Jiangsu Basic Research Project, and the State Key Laboratory of Palaeobiology and Stratigraphy. 

Artistic reconstruction of Cordaticaris striatus on the Cambrian sea (Image by Joschua Knüppe) 

Cambroraster cf. falcatus from the Cambrian (Miaolingian, Wuliuan) Upper Shale Member, Mantou Formation in Weifang City, Shandong Province, North China, and the dorsal (left) view and ventral (right) view of a Cambroraster model (Image by NIGPAS)