Abstract :
[en] The coexistence of sympatric predatory marine reptiles in the Late Cretaceous suggests
ecological partitioning of higher trophic niches. The Western Interior Seaway, a vast inland sea
that stretched across a significant portion of North America, was home to a diverse array of
marine life, most notably a multitude of reptilian predators.
Previous studies have utilized tooth morphology and dental microwear as proxies for
inferring the feeding habits of marine reptiles. However, teeth are only part of the feeding
apparatus. Ecological insights may be elucidated through biomechanical simulations of
craniodental remains, focusing on mechanical performance.
Here, we performed the first, large-scale, comparative study on WIS marine reptile jaw
performance using high-definition three-dimensional models and muscle-driven finite element
analyses (FEA). The jaws of mosasaurids and polycotylid plesiosaurians from the
Campanian-Maastrichtian were 3D scanned and processed for FEA simulations. For comparative
purposes, mosasaur jaws were modeled with a fused symphysis and immobile intramandibular
joint, forming a single functional element. Muscle insertions were identified to reconstruct jaw
adductor muscles and assess respective muscle and bite force. We used Metafor to simulate
realistic, muscle traction dynamics during biting, including simulations at different opening
angles and biting locations.
Results revealed distinct stress distributions per morphotype, demonstrating biomechanical
variation between robust mosasaur mandibles (e.g. Globidens) and the more gracile mandibles of
polycotylids and the mosasaurid Clidastes. Integrating mechanical efficiency with the
deformation sustained by the jaws provided additional ecological inferences. High deformation values in polycotylid jaws suggest that maximum bite force (estimated from muscle attachments) was not exerted, resulting in divergent feeding techniques to mosasaurs (e.g., snapping and swallowing). Moreover, polycotylids and some mosasaurid taxa (e.g., Clidastes and Jormungandr) appear better adapted to biting at wider gape angles, whereas mosasaurids with high mechanical efficiency at wide and narrow gape angles (e.g., Mosasaurus and Prognathodon) are more suited to prey on larger items with powerful bites.
Our results align with niche partition inferences from dental remains and offer deeper
insight into feeding techniques in Late Cretaceous marine predators, providing a unified canvas
and protocol to assess niche partitioning in sympatric marine reptiles from well-sampled (and
well-preserved) regions.
