Analysis and New Records of Billfish (Teleostei: Perciformers: Istiophoridae) from the Yorktown Formation, Early Pliocene of Eastern North Carolina at Lee Creek Mine

Five species of the billfish family Istiophoridae (Istiophorus platypterus (Shaw and Nodder), Makaira indica (Cuvier), M. nigricans Lacepede, M purdyi Fierstine, Tetrapturus albidus Poey) were identified from approximately 500 separate bones collected in the Yorktown Formation (early Pliocene) at Lee Creek Mine, North Carolina. This is the only record of M purdyi, the first fossil record of the genus Tetrapturus (specifically T. albidus), the second fossil record of 1. platypterus and M. indica, and the first record of1. platypterus, M. indica, M. nig­ ricans, and T. albidus from fossil deposits bordering the Atlantic Ocean. Identification was accomplished by converting length and width measurements of individual fossil elements to ratios (proportions), treating them as variables, and comparing them to ratios computed from a large series of bones from extant istiophorid species. Ratios of a fossil specimen that fell outside the range of ratios computed for extant species, or that were equivocal as to genus or species, were identified as one of the following: Istiophoridae, genus and species indeterminate; Istiophorus cf. 1. platypterus; Makaira cf. M. indica; M. cf. M nigricans; M purdyi; cf. Makaira sp.; or Tetrapturus cf. T. albidus. Fifty-three percent of the fossil elements were identified as Istiophoridae, genus and species inde­ terminate, or as M. nigricans. Significant differences (P<0.05) exist between the predentary, rostrum, scapula, and vertebrae 1 and 23 of extant Makaira nig­ ricans and M nigricans from Lee Creek Mine. Features at the extremely significant level (P<O.OO1) are predentaries that are deeper and rounder, rostra that have rounder cross sections and more ventrally placed nutrient canals, and first vertebrae that have a narrower transverse diameter anteriorly. Harry L. Fierstine, BiologicalSciencesDepartment, California Poly­ technic State University, San Luis Obispo, California93407. A review of the natural history and zoogeography of the extant Istiophoridae was used to draw inferences about Lee Creek bill­ fish. The presence ofMakaira indica at Lee Creek Mine suggests that the Panama seaway may have been a migration route for bill­ fish during the early Pliocene. The concentration of billfish at the mine supports the contention that the Yorktown Formation repre­ sents a tropical to warm temperate (21 C) oceanic environ­ ment that was deposited at depths greater than 100 m. Using the width of the rostrum as an estimate of body M. nigricans at Lee Creek Mine probably had a sex ratio of a nonspawning popu­ lation; therefore, I hypothesize that by Yorktown time M. nigri­ cans had already established the present pattern of migrating northward in the western North Atlantic Ocean during the summer to feed after spawning in more southern waters. The fossil history of billfish relevant to the Lee Creek Mine fauna is reviewed and in some cases specimens are reidentified. The family Istiophoridae has a fossil history from the middle Miocene to recent, with the qualification that "Istiophorus" soli­ dus (Van Beneden) (late Eocene, Ghent, Belgium) may be an istio­ phorid. Makaira belgicus (Leriche) (middle Miocene, Anvers, Belgium), 1. cf. I. platypterus (late Miocene, Eastover Forma­ tion, Virginia, United States), and Tetrapturus albidus (early Pliocene, Yorktown Formation, North Carolina, United States) are the oldest known species within their respective genera.