Earliest siphuncle-bearing cephalopod from the early Cambrian.

Eoceras shaanxiense from the early Cambrian represents the earliest known siphuncle-bearing cephalopod, dating back to Cambrian Stage 3.

• Why it matters: Understanding the origin of the siphuncle is crucial for revealing how cephalopods evolved their unique buoyancy regulation and predatory lifestyle, filling a significant gap in mollusc evolution.
• What they did: The study examined a millimetre-sized orthoconic shell with internal septa and a segmented tube, suggesting it functioned as a primitive siphuncle, based on detailed morphological analysis.
• The result: This discovery pushes the origin of stem cephalopods into the early Cambrian, providing insight into the early development of buoyancy-regulating structures and cephalopod evolution.