Ecology of an encrusting fauna on Desquamatia (Atrypida, Brachiopoda) from Cedar Valley formation (Givetian, Devonian) of Iowa, USA

• We examined the biotic interactions of an encrusting fauna and a Devonian atrypide.
• Larger brachiopods were more frequently encrusted than were small hosts.
• Direct interaction between encrusters and their host was rare.
• Direct interaction between encrusters on the same host was rare.
• Space was not a limiting resource in this system.

Encrusting organisms offer a unique window into fossil ecosystems through direct preservation of in situ interactions between host and encrusters and between neighboring encrusters. Herein, we describe a sclerobiont community collected from the Solon Limestone, Cedar Valley Group of Robins Quarry, Iowa. The atrypide Desquamatia (Independatrypa) is frequently encountered in the off-reef carbonates and is commonly encrusted by a moderate diversity of bryozoans, hederellids, auloporid corals, and microconchids comparable to other Devonian sclerobiont communities. This sclerobiont community represents one of few records regarding the paleoecology of Devonian sclerobionts in carbonate settings. Therefore, this study fills a key gap in understanding Devonian pre-extinction ecosystems, given the associated increase in siliciclastic environments during the Devonian mass extinction.In this study, larger Desquamatia brachiopods were more likely to be encrusted. Sclerobionts preferred the convex part of the inflated dorsal valve, likely representing a larval preference for substrates elevated above the sediment–water interface. The life-status relationship between host and sclerobiont is unknown, with rare evidence for either live or dead interactions. Interactions between sclerobionts were rare. Sclerobionts were not space-limited, resulting in a widely distributed, low-interaction sclerobiont community. Our results provide an important insight into sclerobiont communities in carbonate environments, allowing comparison with other Devonian ecosystems as well as providing a reference for comparisons through time.