Unravelling the distribution of decapod crustaceans in the Lower Eocene coral reef mounds of NE Spain (Tremp-Graus Basin, southern Pyrenees)

A highly diverse dromioid crab assemblage (Decapoda, Brachyura) associated with pinnacle reefs in the lower Eocene of Spain

“…Specimens were collected from the outcrop that exposes the transition between the reef limestones and the overlying Riguala Marls at a locality known as “Barranco de Ramals.” A total of 162 specimens of dromioids have been studied from this outcrop. Some of this material (18 carapaces and 17 isolated propodi; 3.1% of total assemblage) was recovered during a detailed paleoecological study of the area in years 2018–2019 (see Ferratges et al, 2021 for more details). The remaining specimens (95 carapaces and 33 isolated propodus) were taken from historical museum collections.…”

“…The Riguala Marls Member, which overlies the reefal unit, has been dated as early to middle Ilerdian (Serra-Kiel et al, 1994), which corresponds to the global Ypresian Stage (Pujalte et al, 2009). This unit formed as a forereef facies in which most of the material was derived from the reef as a result of storm activity, inclusive of the crab specimens described herein (see Ferratges et al, 2021 for more details). Thus, the dromioids, as well as other decapod crustaceans recovered from the same outcrop, lived near these reef pinnacles (Ferratges et al, 2021).…”

“…This unit formed as a forereef facies in which most of the material was derived from the reef as a result of storm activity, inclusive of the crab specimens described herein (see Ferratges et al, 2021 for more details). Thus, the dromioids, as well as other decapod crustaceans recovered from the same outcrop, lived near these reef pinnacles (Ferratges et al, 2021).…”

“…This specific locality corresponds to a reef environment that has already yielded a wide range of decapod crustaceans (Artal and Via, 1989; Artal and Castillo, 2005a; Artal and Van Bakel, 2018a, b; Ferratges et al, 2019). Among the material recognized at this outcrop, dromioids represent only a small portion (3.1%) of the total assemblage (see Ferratges et al, 2021), yet surprisingly, they are unusually highly diverse compared with other Eocene assemblages. This new discovery has prompted a revision of all Eocene dromioid faunules to compare these in terms of diversity and environment with the present material.…”

“…1). This locality has yielded an important assemblage of decapod crustaceans in association with pinnacle coral reefs (Via, 1973;Artal and Via, 1989;Artal and Castillo, 2005a;Fraaije and Pennings, 2006;Artal and Van Bakel, 2018a, b;Ferratges et al, 2019Ferratges et al, , 2021 as well as diverse invertebrate faunas (see Zamora et al, 2018;Ferratges et al, 2021). However, dromioid crabs remained undescribed until now.…”