# A 480-million-year-old parasitic spionid annelid

## TL;DR

Fossils from Morocco reveal that parasitic worms existed 480 million years ago, much earlier than previously thought.

## Contribution

This study presents the earliest known evidence of parasitic spionid annelids from the Early Ordovician period.

## Key findings

- Seven bivalve fossils show shell borings consistent with parasitic spionid polychetes.
- This suggests spionid polychetes existed in the Early Ordovician, 100 million years earlier than previously documented.
- The life history strategy of these worms has remained stable for 480 million years.

## Abstract

The Paleozoic fossil record provides unique insights into the evolution of life history traits through the direct preservation of interspecific interactions in deep time. However, evidence of direct interactions between different species is relatively rare even among localities with exceptional soft-tissue preservation. Here we provide evidence of parasitic organisms from the Fezouata Shale biota of Morocco. Seven specimens of the bivalve mollusk Babinka show highly characteristic, question mark-shaped shell borings consistent with those produced by modern and fossil parasitic spionid polychetes. This suggests that the spionid polychetes, or polychetes with behavior consistent with spionids, were present in the Early Ordovician, a significant biostratigraphic shift in their temporal origins from their accepted Devonian occurrence. Many unique life history strategies which were significant components of the Fezouata Shale biota remain undiscovered, despite the high concentration of taxonomic attention on the site.

•The first evidence of parasitism from best preserved Ordovician fossil site, Fezouata•Parasitic spionids occurred ∼100 million years older than previously known•Life history strategy of these worms has remained stable for 480 million years

The first evidence of parasitism from best preserved Ordovician fossil site, Fezouata

Parasitic spionids occurred ∼100 million years older than previously known

Life history strategy of these worms has remained stable for 480 million years

Natural sciences; biological sciences; paleobiology