First gut contents in a Cretaceous sea turtle

Area of Science:

• Paleontology
• Marine Biology
• Dietary Ecology

Background:

• Modern sea turtles exhibit diverse diets, from herbivory to omnivory.
• The feeding habits of fossil sea turtles remain largely uncharacterized.
• Protostegid turtles have been hypothesized as molluscivores, but their limb morphology suggested surface feeding limitations.

Purpose of the Study:

• To provide the first direct evidence of diet in fossil protostegid sea turtles.
• To investigate the feeding strategies of Lower Cretaceous protostegids (cf. Notochelone).
• To re-evaluate the dietary capabilities of early sea turtles.

Main Methods:

• Analysis of fossilized inoceramid bivalve shell fragments found within the body cavities of protostegid turtles.
• Comparison of shell fragment accumulations with coprolite masses from the same geological deposits.
• Microscopic examination of shell composition and fragmentation patterns.

Main Results:

• Direct evidence of inoceramid bivalve shell fragments within the body cavities of small protostegid turtles (cf. Notochelone) from the Lower Cretaceous of Australia.
• Shell fragments were densely packed, measuring 5-20 mm, and identical accumulations were found in associated coprolites.
• The thin inoceramid shells were ingested in segments, likely with soft tissues and encrusting organisms, indicating consumption of benthic molluscs.

Conclusions:

• Protostegid turtles, specifically cf. Notochelone, regularly consumed benthic molluscs.
• This finding challenges previous interpretations of protostegid feeding limitations based on limb morphology.
• Fossil protostegids likely possessed a broader range of feeding habits, similar to modern sea turtles.