New evidence of the global distribution of the swordfish-like pachycormid Protosphyraena in the late Early Cretaceous and a review of global records of the genus

Abstract

Protosphyraena is one of the most widespread Cretaceous actinopterygian genera, with numerous species described primarily from the Upper Cretaceous of North America and Western Europe. However, most of the species are known from fragmentary and anatomically non-overlapping material, making the alpha taxonomy of this genus extremely problematic. Here we describe the first finds of Protosphyraena from the Albian of the Caucasus, and reassess the historical specimens from the Cenomanian of the Kursk Region of Russia. In an attempt to assign Russian specimens to a particular species, we review the global records and tangled taxonomy of Protosphyraena. The type species, P. ferox, is unambiguously known from teeth, cranial fragments and mandibles. The posteriorly directed rostral teeth of the type species cast doubt on the validity of Australopachycormus originally erected based on this feature. Our observations support the assignments of the historical Russian Cenomanian specimens to P. ferox and P. tenuirostris. We do not find sufficient cause to refer all isolated fins from Europe to P. ferox, as suggested by recent research. Instead, the species initially proposed by Agassiz for isolated fins from the English Chalk are available, and the fins of Protosphyraena from the Caucasus are consistent with one of these species, Protosphyraena gibberula comb. nov. Our findings indicate that Protosphyraena was widespread already in the late Early Cretaceous. Moreover, the youngest occurrence of Protosphyraena in Europe, a pectoral fin from the Maastrichtian of Belgium, demonstrates unique features and is thus referred to a new species, Protosphyraena terminata sp. nov.