New Early Cenozoic ghost shrimps (Decapoda Axiidea Callianassidae) from Pakistan and their palaeobiogeographic implications

摘要

A new set of Paleocene and Eocene decapod crustaceans is described from the Kirthar Range of Pakistan. Two new ghost shrimps (Crustacea, Decapoda, Callianassidae) are described: Neocallichirus khadroensis Hyžný & Charbonnier, n. sp. from the Paleocene (Danian, Khadro Formation) of Gawar Band, Ranikot District, and Neocallichirus lakhraensis Hyžný & Charbonnier, n. sp. from the Early Eocene (Ypresian, Lakhra Formation) of Rbod Nala, Jhirak District. Both new species exhibit chelipeds which are morphologically surprisingly close to extant Neocallichirus karumba () from the Indo-West Pacific. A group of species sharing this same cheliped morphology is provisionally called the “karumba group” based on Neocallichirus karumba, best documented species. The “karumba group” encompasses seven fossil species: the two new Pakistani species, Neocallichirus tuberculatus (Lőrenthey in ) n. comb. from the Eocene of Hungary, Neocallichirus borensis from the Eocene of Italy, Neocallichirus birmanicus () n. comb. from the Miocene of Myanmar, Neocallichirus dijki () from the Miocene of Java and Philippines, and the subfossil Neocallichirus maximus (A. ) from Thailand. Based upon the extant and fossil occurrences, it is difficult to reconstruct migration pattern of the “karumba group”. For now, it can be concluded, that at the genus level, a relative homogeneity of the ghost shrimps is observed between the Eastern and the Western Tethyan regions, as already suggested by for the assemblage of volutid gastropods from the Lakhra Formation.