Finite element and microstructural analyses indicate that pteraspid heterostracan oral plate microstructure was...

Area of Science:

• Paleontology
• Vertebrate Evolution
• Biomechanics

Background:

• Early vertebrate evolution proposed a shift from passive to active feeding.
• Feeding ecology of extinct stem-gnathostomes, like heterostracans, is poorly understood.
• Pteraspidiform heterostracans had oral plates with debated feeding functions (suspension vs. mechanical).

Purpose of the Study:

• To test the mechanical function hypothesis of pteraspidiform oral plates.
• To investigate the feeding strategies of early gnathostome stem-lineage members.

Main Methods:

• Microstructural analysis of oral plate bone.
• Finite element analysis (FEA) to simulate stress distribution.
• Examination of wear patterns on oral plates.

Main Results:

• A negative correlation was found between compressive stress and bone volume fraction.
• Oral plate shafts showed higher stress, and hooks (load application points) had the highest bone density.
• Wear patterns suggest abrasive polishing consistent with mechanical food processing.

Conclusions:

• The skeletal microstructure of oral plates adapted to mechanical loads, rejecting suspension feeding.
• Heterostracan oral plates likely functioned in mechanical food processing (e.g., deposit feeding, scavenging).
• This supports a more active feeding role in early vertebrate evolution.