A salamander that chews using complex, three-dimensional mandible movements

Area of Science:

• * Vertebrate Paleontology
• * Comparative Biomechanics
• * Evolutionary Biology

Background:

• * Non-mammal tetrapods typically exhibit simple, vertical jaw movements for feeding.
• * Complex three-dimensional (3D) jaw motions, including propalinal and transverse movements, are characteristic of mammals.
• * Lissamphibians and sauropsids are generally believed to swallow food largely unreduced, with limited chewing capabilities.

Purpose of the Study:

• * To investigate the intraoral food processing and jaw kinematics of the paedomorphic salamander *Siren intermedia*.
• * To determine if complex 3D jaw movements occur in non-mammalian tetrapods.
• * To challenge the prevailing view that advanced chewing mechanisms are exclusive to mammals.

Main Methods:

• * Combined 3D kinematics using biplanar high-speed video fluoroscopy.
• * Morphological analyses utilizing micro-computed tomography.
• * Analysis of mandibular motion in three planes (vertical, propalinal, transverse).

Main Results:

• * *Siren intermedia* engages in intraoral food processing.
• * The salamander possesses an elaborated jaw joint morphology.
• * This morphology facilitates complex 3D mandibular movements, enabling sophisticated chewing.

Conclusions:

• * Complex 3D chewing is not exclusive to mammals.
• * Sophisticated jaw movement mechanisms may have evolved earlier in tetrapod evolution.
• * *Siren intermedia* provides evidence for early evolution of complex feeding strategies.