Overview
- A peer-reviewed iScience study led by UC Riverside’s Karma Nanglu identifies question mark–shaped traces in Moroccan Ordovician bivalves as the work of spionid annelid worms.
- High-resolution micro-CT imaging exposed matching markings on shell surfaces and within the shells, with several repeated traces on individual specimens.
- Comparisons with modern observations provided a “smoking gun” image showing the same internal shape made by living spionid worms.
- The inferred life cycle begins with larval settlement and localized shell dissolution for anchoring, followed by deeper burrowing that produces the distinctive question mark geometry.
- Scanning also uncovered additional parasitized shells hidden in layered rock, and the same behavior today weakens oyster shells and can raise mortality in commercial fisheries.