Earliest siphuncle-bearing cephalopod from the early Cambrian

Recent cephalopods are the most intelligent invertebrates and are unique among molluscs in possessing chambered, gas-filled shells penetrated lengthwise by a siphuncle that regulates buoyancy, enabling their nektonic and predatory lifestyle through jet propulsion. The origin of this key innovation remains enigmatic, as there is a major gap between the earliest known cephalopod, Plectronoceras cambria from the late Cambrian, and molecular clock estimates that place the lineage’s divergence from other molluscs in the early Cambrian. Here we report millimetre-scale, orthoconic shells tentatively assigned to Cupitheca sp. from the Shuijingtuo Formation (Cambrian Stage 3) of South China. Internally, the shells exhibit multiple septa and a peripherally situated segmented tube, indicating that the soft body migrated anteriorly to form successive chambers during growth while maintaining contact with earlier chambers via the tube. Collectively, these features identify the segmented tube of Cupit..., , # Earliest siphuncle-bearing cephalopod from the early Cambrian

Dataset DOI: [10.5061/dryad.qbzkh18zk](https://doi.org/10.5061/dryad.qbzkh18zk)

## Description of the data and file structure

Micro-CT scanning data was performed on specimens CUBar297 (GQ-LYB-4)-1(**20231122_gjf_Bar297-1_3.72um-tiff.zip**), CU(CT-cupitheca)-7(**20260106_gjf_cupi-7_2.72um_tiff.zip**) and CU(CT-cupitheca)-11(**20260107_gjf_cupi-11_2.04um_tiff.zip**) with the Zeiss Xradia 520 system at the State Key Laboratory of Continental Dynamics of Northwest University in Xi’an, Shaanxi Province, China.

Scanning conditions were 40 kV accelerating voltage, 80 μA beam current, and an isotropic voxel size of 3.72 μm, 2.72 μm and 2.04 μm, respectively. Approximately 1,000 projection images were acquired in TIFF format. Data were reconstructed using standard, filtered back-projection algorithms and visualized in VG Studio Max 2.2 for three-dimensional volume rendering and segmentation.

## Code/software

VG Studio Max 2...., ,