Computer Simulations Imply Forelimb-Dominated Underwater Flight in Plesiosaurs

Area of Science:

• Paleontology
• Marine Biology
• Biomechanics

Background:

• Plesiosaurians were highly derived marine reptiles inhabiting Earth for 135 million years.
• Their unique body plan featured two pairs of large, wing-like flippers, but their locomotion remains debated.
• Controversies include the limb stroke mechanism (rowing vs. underwater flight) and limb coordination.

Purpose of the Study:

• To investigate plesiosaur locomotion using a novel simulation approach.
• To determine the most efficient limb stroke and coordination for plesiosaur swimming.
• To explore how locomotory repertoire changes under different parameters.

Main Methods:

• Developed a digital, three-dimensional, articulated, free-swimming plesiosaur model.
• Conducted numerous simulations in a simulated fluid environment.
• Varied joint degrees of freedom to analyze locomotory changes.

Main Results:

• Simulated plesiosaurs primarily used forelimbs for propulsion via an unmodified underwater flight stroke.
• Hind limbs generated relatively weak thrust across all simulated conditions.
• Forelimb-dominated swimming was most efficient within biologically plausible ranges.

Conclusions:

• Plesiosaurs were predominantly forelimb-dominated swimmers.
• The hind limbs likely served secondary roles in maneuverability and stability.
• This study clarifies a long-standing debate on plesiosaur locomotion.