Exceptionally preserved pea crabs (Decapoda, Brachyura, Pinnotheroidea) from the Miocene St. Marys Formation, eastern USA, exhibiting preferential symbiosis with the surf clam Mactrodesma subponderosa (Ward, 1992)

2026/07/01 by Stephen C Groff, Victor J Perez, Carrie E Schweitzer +2

paper · doi:10.1093/jcbiol/ruag041

Abstract

Abstract A new fossil pinnotheroid crab, Pinnotheres prochowniki n. sp., from the upper Miocene (Tortonian) Little Cove Point Member of the St. Marys Formation of Maryland, USA, and St. Marys or Eastover Formation of Virginia, USA, is described based on sixteen specimens, marking the first occurrence of a pinnotheroid from the Chesapeake Group. These pinnotheroids exhibit remarkable preservation, many specimens of which are fully articulated, and at least one specimen retains preserved pleopods and gills. These crabs also appear to exhibit preferential association with the surf clam Mactrodesma subponderosa Ward, 1992, with all but two being found within their shells and none being found in association with any other potential host species. The exceptional preservation of these pea crabs can be attributed in part to this symbiotic relationship, as the host clam served to protect the crabs from being destroyed by taphonomic processes.

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