# Discovery of diverse Pectocaris species at the Cambrian series 2 Hongjingshao formation Xiazhuang section (Kunming, SW China) and its ecological, taphonomic, and biostratigraphic implications

## TL;DR

This study discovers new Pectocaris species in China's Cambrian rock layers, revealing ecological adaptations and connections between ancient marine ecosystems.

## Contribution

The discovery of a new Pectocaris species and its ecological interpretation expands understanding of Cambrian biodiversity and niche differentiation.

## Key findings

- Pectocaris paraspatiosa sp. nov. is identified as a filter-feeder adapted to shallow, agitated environments.
- Morphological differences among Pectocaris species suggest niche differentiation within the genus.
- The study establishes a biological connection between Yu’anshan and Hongjingshao Formations through shared fossil taxa.

## Abstract

Pectocaris species are intermediate- to large-sized Cambrian bivalved arthropods. Previous studies have documented Pectocaris exclusively from the Cambrian Series 2 Stage 3 Chengjiang biota in Yu’anshan Formation, Chiungchussu Stage in SW China. In this study, we report Pectocaris paraspatiosa sp. nov., and three other previously known Pectocaris from the Xiazhuang section in Kunming, which belongs to the Hongjingshao Formation and is a later phase within Cambrian Stage 3 than the Yu’anshan Formation. The new species can be distinguished from its congeners by the sparsely arranged endopodal endites and the morphologies of the abdomen, telson, and telson processes. We interpret P. paraspatiosa sp. nov. as a filter-feeder and a powerful swimmer adapted to shallow, agitated environments. Comparison among the Pectocaris species reinforces previous views that niche differentiation had been established among the congeneric species based on morphological differentiation. Our study shows the comprehensive occurrences of Pectocaris species outside the Chengjiang biota for the first time. With a review of the shared fossil taxa of Chengjiang and Xiaoshiba biotas, we identify a strong biological connection between the Yu’anshan and Hongjingshao Formations.