New isopod and achelatan crustaceans from mid–Cretaceous reefal limestones in the Basque-Cantabrian Basin, northern Spain

Abstract

Mid-Cretaceous (upper Albian) strata of the Basque-Cantabrian Basin in northern Spain are renowned for their highly diverse crustacean assemblages from reef settings. From the Koskobilo quarry, two small, enrolled specimens of a sphaeromatid isopod, Cymodoce (?) scopula sp. nov., and the posterior part of a carapace of a palinurid achelatan, Palaeopalinurus serratus sp. nov., are recorded. In view of the remarkably complete preservation of the isopod specimens, this example ranks amongst those extinct isopods that can be tentatively placed within an extant genus. Cymodoce (?) scopula sp. nov. would constitute the stratigraphically oldest member of this genus to date, extending its range by 65 myr. With regard to the taxonomy of extinct isopods, Sphaeroma gasparellai from the Eocene of Italy is here transferred to Cymodoce, Cymodoce sarmatica is regarded as incertae sedis within Isopoda, and Triassphaeroma magnificum from the Upper Triassic of Italy is placed in the family Cirolanidae. Finally, Reboursia ranvillensis from the alleged Middle Jurassic (upper Bathonian, but possibly Cenozoic) of northwest France best fits in the family Sphaeromatidae. The new palinurid is the youngest representative of Palaeopalinurus thus far. The new palinurid species affirms that Koskobilo and the Albeniz unit are the richest locality and stratigraphic unit for Cretaceous decapods to date. Koskobilo is also one of the most diverse Cretaceous localities for crustaceans