The first record of paguroids from the eocene of Istria (Croatia) and further phylogenetic refinement of the Paguroidea (Crustacea, Anomura)

Abstract

A paguroid, Lessinipagurus vasjamikuzi sp. nov., is described from Eocene (upper Bartonian–lower Priabonian) of Istria, on the basis of a single right chela from Gračišće near Pazin, western Croatia. The specimen originates from beds of olistostrome breccias that formed in a bathyal setting. In addition, a new genus, Prexylopagurus, accommodated in the new family Xylopaguridae, is erected; based on a distinctive set of characters of the dorsal carapace, chelae, and operculate tergite of sixth abdominal somite. The phylogenetic relationships of the new family Xylopaguridae are discussed; it appears to have originated in the Tethyan Realm, possibly as early as the Jurassic, and displays a Tethyan distribution during the Cenozoic. Three extant species are transferred to the new genus, resulting in three new combinations: Prexylopagurus anthonii, P. philippinensis, and P. caledonicus. The palaeoecology and palaeobiogeography of the newly erected taxa are discussed. The bloom of diversity of Lessinipagurus during the late Eocene parallels the evolution and subsequent ecological expansion of grasses, especially of reed and bamboo, thus constituting a rare example of coevolution between land plants and marine organisms. The holotype of Lessinipagurus vasjamikuzi sp. nov. shows remains of an interesting syn-vivo balanomorph association; this is the earliest record of such barnacles on a decapod crustacean in the fossil record, and the sole record from an anomuran to date.