A fossil skull of the extant blue marlin (Makaira nigricans Lacepede, 1802) from the late Miocene of Orange County, California.(Report)

Abstract.--A nearly complete fossil skull, including the rostrum, of blue marlin, Makaira nigricans Lacepede, 1802 (Perciformes: Xiphioidei: Istiophoridae), was collected from the Oso Member (latest Miocene) of the Capistrano Formation, Mission Viejo, Orange County, California. The specimen is compared with extant and fossil istiophorids, and 19 of its 20 morphological variables are within the range of values observed for extant M. nigricans, whereas only 13 or less variables are within the observed range of other extant istiophorids. Because extant M. nigricans usually inhabits a water column with a height of about 200 m or more and is the most tropical of all xiphioid species, its presence supports the hypotheses that the Oso Member was deposited at upper bathyal depths or greater and that the coastal paleoclimate of southern California was warmer during the late Miocene than at present.

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The extant blue marlin, Makaira nigricans Lacepede 1802, (Perciformes: Xiphioidei: Istiophoridae) is an important commercial and recreational fish species that inhabits the tropical and temperate Atlantic, Indian, and Pacific oceans, various strata within a water column of about 200 m or more and average sea surface temperatures of approximately 24[degrees]C (Nakamura 1985). The blue marlin is rarely observed off the coast of southern California (Eschmeyer et al. 1983).

According to Fierstine (2006), the blue marlin or blue marlin-like xiphioids (M. cf. M. nigricans) are the most common fossils of the Family Istiophoridae. The earliest records are from the late Miocene where M. nigricans was identified in two rock units in southern California, the Monterey and San Mateo formations (Fierstine and Applegate 1968; Fierstine and Welton 1988; Fierstine 1998, 2001), and M. cf. M. nigricans was identified in three late Miocene rock units, the Eastover Formation, Virginia, U.S.A. (Fierstine 1998), Gatun Formation, Panama (Fierstine 1999), and Pietra leccese, Italy (Carnevale et al. 2002). In addition, blue marlin and blue marlin-like specimens also were described from the Trinidad Formation, Baja California Sur, Mexico, but because the age of the deposit ranges from late Miocene to late Pliocene (Fierstine et al. 2001), the specimens may or may not rank among the earliest known records of M. nigricans. The specimens from the two southern California localities were originally identified only to genus (Makaira sp.) (Fierstine and Applegate 1968; Fierstine and Welton 1988), but were re-identified by Fierstine (1998, 2001) after more comparative material became available.

In 1980, Hugh Wagner, during a paleomitigation project for the Mission Viejo Company, collected a nearly complete skull of M. nigricans, OCPC 31001 (Orange County Paleontology Collection), from the Oso Member (latest Miocene) of the Capistrano Formation near the current northern city limit of Mission Viejo, Orange County, California (Fig. 1). According to Barnes and Raschke (1991), the Oso Member is correlative with all but the latest Hemphillian North American Land Mammal Age [4.6 to 9.0 Ma (Woodburne and Swisher 1995)]. Although the specimen is the third record of a blue marlin in late Miocene deposits of southern California (Fierstine 2006), it is the only one with a skull and rostrum, and warrants description.

Materials and Methods

Approximately 160 whole and partial skeletons of extant (= Recent or Holocene) specimens, representing seven species of the family Istiophoridae, were examined and used for comparison with the fossil skull. The scientific and common names of Nelson et al. (2004) are used for Recent istiophorids with the exception that I follow Orrell et al. (2006) and place the istiophorids in the suborder Xiphioidei, and Collette et al. (2006) who recognize only one species of blue marlin (M. nigricans) instead of two species [M. nigricans and M. mazara (Jordan and Snyder 1901)]. A combination of the osteological terminology of Arratia (1997), Davie (1990), Gregory and Conrad (1937), Gudger (1940), Rojo (1991), and Schultz (1987) is used.