Specimens of the billfish Xiphiorhynchus Van Beneden, 1871, from the Yazoo Clay Formation (Late Eocene), Louisiana

Abstract

In 1974, Fiersline and Applegate described a new species of billfish, Xiphiorhynchus kimblalocki, based on a rostrum, two vertebrae, and two partial fin spines, from the Yazoo Clay For­ mation, late Eoccne, Mississippi, U.S.A. This was the first sub­ stantiated record of Xiphiorhynchus van Beneden, 1871, outside of western Europe. Since this initial discovery, there have been three other records of Xiphiorhynchus in the United States. Based on four rostral fragments, Breard and Stringer (1995) listed Xiphiorhynchus among the numerous marine vertebrates they collected in the Yazoo Clay Formation, late Eocene, Loui­ siana. There was no formal description and identification was restricted to the generic level. Fierstine and Starnes (2005) iden­ tified X. cf. X. eocaenicus (Woodward, 1901), in the Moodys Branch Formation, middle Eocene, Mississippi, based on com­ parison with X. eocaenicus (Woodward, 1901), from the Brack­ lesham Beds, middle Eocene, England. Monsch and colleagues (2005) confirmed that the holotype of X. rotundus (Woodward, 1901), a featureless, phosphate impregnated rostrum with a vague provenance, was collected in the late Oligocene or early Miocene of the Charleston region, Soulh Carolina. Here we report new specimens (three partial rostra) of Xi­ phiorhynchus that were collected in the Yazoo Clay Formation, late Eocene, Louisiana, U.S.A. Two of the better preserved specimens are identified as X. kimblalocki, and although the third specimen is poorly preserved and only identified to genus, il belongs to a species distinct from X. kimblalocki. We compare all three specimens to other species of Xiphiorhynchus and discuss the difficulty in confirming the identity of rostra that have been referred to X. priscus (Agassiz, 1844) because the holotype of X. priscus is a poorly preserved skull without a ros­ trum.