Abstract

Five species of the billfish family Istiophoridae (Istiophorus platypterus (Shaw and Nodder), Makaira indica (Cuvier), M. nigricans Lacépède, 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 I. platypterus and M. indica, and the first record of I. platypterus, M. indica, M. nigricans, 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 ofbones 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. I. 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 indeterminate, or as M. nigricans.

Significant differences (P<0.05) exist between the predentary, rostrum, scapula, and vertebrae 1 and 23 of extant Makaira nigricans and M. nigricans from Lee Creek Mine. Features at the extremely significant level (P<0.001) 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.

Disciplines

Biology

 

URL: http://digitalcommons.calpoly.edu/bio_fac/21