The first record of the pachycormid fish Bonnerichthys in Eurasia marks a global distribution of Late Cretaceous suspension-feeding giants

Abstract

The giant Late Cretaceous suspension-feeding pachycormid Bonnerichthys has puzzled researchers since it was named, as its geographic distribution is confined to the USA, which contrasts with other widespread Jurassic and Cretaceous pachycormid genera. Here we describe fin fragments of Bonnerichthys from the Campanian of European Russia. The fins have a characteristic structure of the anterior edge, which is strongly thickened with its leading edge forming a sharp but irregularly excavated keel; internally the fins have a specific ossification with wedge-shaped structure between the rays. These features are autapomorphic of Bonnerichthys and thus allow for positive assignment of the Russian specimens to this genus. This is the first direct evidence of the presence of Bonnerichthys outside the USA, which solves the mystery of its seemingly restricted distribution and highlights that all large suspension-feeding pachycormids were cosmopolitan during their Jurassic and Cretaceous evolutionary history.