New records of Eogastrodorus (Decapoda, Anomura, Gastrodoridae) from the Middle Jurassic (Bajocian) of England and France

Abstract

Of the anomuran Eogastrodorus granulatus (Förster, 1985), the sole representative of the genus, only the holotype from Bajocian strata in Switzerland was known until now. The five additional specimens described here have enabled us to supplement the morphological characterisation of both the genus and species. Of these five individuals, four originate from the shallow-marine Sherborne Limestone Member (Inferior Oolite Formation, lower upper Bajocian) in southern England. The fifth is from the shallow-marine biodetritic Audun-le-Tiche Limestone in Lorraine (France), of late early Bajocian ( Humphriesianum Zone) age; this is the stratigraphically oldest record of a gastrodorid known to date. Two juvenile carapaces from England are preserved within a piece of driftwood. We offer three possible interpretations for this occurrence; the hollowed out inside of the wood could have provided a place for moulting, retreating or mating. Alternatively, the two carapaces represent the remains of a meal of a predator that lived inside the wood or took shelter there, or, thirdly, it could constitute a random influx of carapaces into the empty space of the piece of wood. Each of these scenarios presupposes that these anomurans lived in an onshore habitat, where driftwood of all sizes is frequently encountered. These taphonomic circumstances could represent the earliest instance of the relationship between paguroids and plants.