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Exploring the influence of cameral deposits on the stability; orientation; and maneuverability of orthocone cephalopods
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DOI：10.1017/pab.2025.10085.png)
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Abstract
En 中文
Orthoceratoid cephalopods had straight or slightly curved shells that often contained enigmatic calcareous structures in their chambers. These cameral deposits have been interpreted as counterweights; allowing these cephalopods to assume postures other than a default; downward-facing orientation. These animals must have balanced the proportions of their soft body; cameral deposits; and air-filled chambers to maintain a condition near neutral buoyancy. Lower body chamber ratios (BCRs) allow more mass to be dedicated to cameral deposits; increasing their influence over the total mass distribution. Using 43 computer reconstructions; we calculated the proportion of chamber contents that satisfy a neutrally buoyant condition across different BCRs. Furthermore; we explored the limits of cameral deposit distributions inside the shell to better understand their influence over orientation; stability; and maneuverability. Cephalopods with 40% BCR cannot accommodate any deposits and assume stable; downward-facing orientations. Cephalopods with 30% BCR allow some cameral deposits; which negligibly reduce stability. A slight reduction in BCR to 25% can considerably improve maneuverability; allowing these cephalopods to assume a wider range of postures while swimming. While our results are most relevant to some subset of orthocone cephalopods (Pseudorthoceratida); we also highlight similar constraints faced by broader orthocone groups. Swimming capabilities are extremely sensitive to BCR; which likely constrains the life habits and ecology of these animals. Our results add context to (1) the physical constraints of orthocone cephalopods; (2) their functional complexity in Paleozoic ecosystems; and (3) how these early swimmers navigated physical trade-offs between stability and maneuverability.
Keywords:
cameral deposits
orthocone cephalopods
buoyancy
stability
maneuverability
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