Houcaris gen. nov. from the early Cambrian (Stage 3) Chengjiang Lagerstatte expanded the palaeogeographical distribution of tamisiocaridids (Panarthropoda: Radiodonta)

Radiodonts were cosmopolitan and diverse stem-euarthropods that have been generally regarded as the apex Cambrian predators. Four major groups have been distinguished including tamisiocaridids, primarily based on the endite features of the frontal appendages. Anomalocaris saron Hou, Bergstrom and Ahlberg, 1995, one of the most well-known radiodonts in the Chengjiang Lagerstatte, is generally treated as a member of the Family Anomalocarididae. New anatomical evidence reported here, allied with the data of microcomputed tomography (CT) shows that the endites in A. saron are paired, much longer than the height of associated podomeres, and furnished with multiple slender distal auxiliary spines. These new observations allow us to reassign A. saron to a new genus, Houcaris gen. nov., and strongly support its tamisiocaridid affinities rather than anomalocaridid as previously suggested. Houcaris saron, thus, represents the first tamisiocaridid species known from South China, as well as the oldest tamisiocaridid in the fossil record (Cambrian Stage 3). Our occurrence data, coupled with other distribution of tamisiocaridids, demonstrate that this group is restricted to the early Cambrian (Series 2), and occur across South China, Laurentia and eastern Gondwana within tropics/subtropics belt, indicating a possible climatic control on their distribution. Moreover, these tamisiocaridid records documented in several Konservat Lagerstatten suggest an ecological preference to shallow water environment with well-oxygenated sea bottom conditions.

Automated summary

The study reassigns Anomalocaris saron to a new genus, Houcaris gen. nov., and supports its tamisiocaridid affinities. Houcaris saron represents the first tamisiocaridid species known from South China and the oldest in the fossil record. The tamisiocaridid group is restricted to the early Cambrian, possibly indicating a climatic control on their distribution.