View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by DigitalCommons@CalPoly Reprinted from: Stroud. Richard H. (ed.). 1990. Planning the Future of Billfishes. Part 2. COlltrib~ted Papers. Proceedings of the Second Intem.~tlonal Billfish Symposium, Kailua-Kana, HawaII, August 1-5, 1988. A Paleontological Review of Three Billfish Families (Istiophoridae, Xiphiidae, and Xiphiorhynchidae) Harry L. Fierstine In 1974, I summarized the osteological and the taxonomic nomenclature of Nakamura paleontological knowledge of billfishes and (1983), with the exception that I agree with Robins suggested some areas of research to aid future and de Sylva (1960) that both the sailfish and paleontological studies (Fierstine 1974). My blue marlin exist as single world-wide species, suggestions included: (l) a comparative osteo­ and not as separate Atlantic Ocean and Pacific logical study, especially of the rostrum, in order Ocean forms. to obtain more accurate identifications of fos­ Family Xiphiidae silized material; (2) a functional study of the Xiphias Linnaeus feeding mechanism, in order to explain observed Xiphias gladius Linnaeus, 1758 ­ interfamilial differences in the skull; (3) a func­ Swordfish tional study of the locomotor apparatus in order Family Istiophoridae to elucidate inter- and intrafamilial differences Istiophorus Lacepede in vertebrae, body shape and fin morphology, Istiophorus platypterus (Shaw and and (4) a more thorough study of those extinct Nodder, 1792) - Sailfish families (Blochiidae and Paleorhynchidae) and Makaira Lacepede genera (Acestrus and Brachyrhynchus) having Makaira indica (Cuvier, 1832) - Black uncertain affinities to other billfishes. marlin Since 1974, some of the foregoing items, as Makaira nigricans Lacepede, 1802­ well as some not listed, have been studied with Blue marlin varying degrees of thoroughness. In the most Tetrapturus Rafinesque comprehensive treatise, Schultz (1987) investi­ Tetrapturus albidus Poey, 1860­ gated all extant and extinct billfishes and White marlin developed a new taxonomic arrangement and Tetrapturus angustirostris Tanaka, 1915 evolutionary scheme based primarily on structure - Shortbill spearfish of the rostrum. The present study reviews the Tetrapturus audax (Philippi, 1887)­ published accounts, presents some new informa­ Striped marlin tion, and summarizes the relevant osteological Tetrapturus belone Rafinesque, 1810­ and current paleontological knowledge of three Mediterranean spearfish billfish families (lstiophoridae, Xiphiidae, and Tetrapturus georgei Lowe, 1840­ Xiphiorhynchidae) . Roundscale spearfish Tetrapturus pfluegeri Robins and de Systematics of Recent Forms Sylva, 1963 - Longbill spearfish Al'.hough Schultz (1987) rearranged the extant billfishes into three families (lstiophoridae), Relevant Osteology of Recent Forms Tetrapturidae, and Xiphiidae) and six genera Skull (Istiophorus, Makaira, Marlina, Pseudohis­ General account and terminology. I will follow tiophorus, Tetrapturus, andXiphias), I will follow the lead of other billfish scientists (e.g., Nakamura 11 12 PLANNING THE FUTURE OF BILLFISHES 1983) and use the osteological terminology of three istiophorid genera can be distinguished by Gregory (1933) and Gregory and Conrad (1937) the shape of their rostra at the rostral mid-point where possible even though it may not conform (Fig. 2). The distribution of denticles (Table I) to modern comparative developmental studies and relative size of the paired nutrient canals (Jollie 1986). Myer et al (in press) and Schultz show interspecific patterns. (1987) independently discovered that the Schultz (1987) noticed that the denticles along istiophorid rostrum contained a new paired ele­ the ventral midline of the rostrum of the shortbill ment, the prenasal, which had mistakenly been spearfish and Mediterranean spearfish are not considered part of the premaxillary bone by housed in alveoli and detach when the rostra are other workers. prepared into skeletons. He separated all spear­ Rostrum. The rostrum (or bill) is defined as fishes (T. angustirostris, T. belone, T. georgei, that part of the snout which extends anteriorly and T. pfluegeri) from the other billfishes from the anterior border of the bony orbit to primarily on the basis of the edentulous zone. terminate in a projection beyond the lower jaw There was no mention of intraspecific or in­ (Fierstine 1978). The Istiophoridae and Xiphiidae terspecific variation of the character. have rostra with different morphologies. Poplin et al (1976) described the microscopic The swordfish bill is flattened in cross-section, anatomy of the swordfish rostrum. It is com­ lacks denticles in the adult (Carter 1919), and posed superficially of a thin layer of acellular usually contains a longitudinal series of central primary bone that has the appearance of dentine. chambers (Poplin 1975, 1976; Poplin et al 1976; The superficial layer is underlain by acellular Schultz 1987) that demonstrate considerable in­ vascular bone containing secondary osteons traspecific variation. In an X-ray examination (Haversian units) which are arranged into large of 39 rostra, I found 24 with chambers running bundles in the deeper regions (center) of the the entire length of the rostrum, five with cham­ sword. There are no comparable histological bers only in the distal one-half, seven with cham­ studies of istiophorid rostra. bers only in the distal one-fourth, and three with Lower jaw. With the exception of mentioning no chambers. There is a minor controversy over the presence or absence of the predentary bone, which bones form the swordfish rostrum. Gregory there are no published studies of other features and Conrad (1937) discussed the problem and of the lower jaw. The istiophorids have a stout concluded that the distal three-fourths is primarily mandible that is composed of the predentary, composed of premaxillae with paired nasals on dentary, and articular bones. There is a well­ the dorsal surface. The proximal one-fourth is developed intermandibular joint and each mandi­ composed of the dermethmoid, frontals, maxilla­ ble has a strong cone-shaped quadrate-articular ries, lateral ethmoids, and vomer. After dissecting joint. In contrast, the swordfish has a much a juvenile swordfish, Conrad (1937) concluded weaker lower jaw with no predentary bone or that the true nasal is "a minute but well-formed intermandibular joint. It has a rather simple bony element lying dorsad to the narial open­ quadrate-articular articulation. ings" and the bones that Gregory and Conrad Intrafamilial variation is unknown. The obser­ (1937) called nasals were just parts of the pre­ vation, however, that the shortbill spearfish has maxillae. To the best of my knowledge, all sub­ its predentary bone reduced to a tooth patch sequent workers (Nakamura 1983; Poplin et al (Fierstine and Applegate 1968), is incorrect 1976; Schultz 1987), except Johnson (1986), because the observation was based on an ab- have followed Gregory and Conrad (1937) and, not Conrad (1937). If most authors are correct, Table I. Relative length of denticulated area on dorsum ofrostrum offive species ofextant billfishes. Relative len[?th then X. gladius lacks the prenasal bones found was determined by dividin[? the length of the denticulated in istiophorids. However, if Conrad (1937) and zone by L (see Fig. 2 legend for definitio/l). Johnson (1986) are correct, then it is possible Number Average relative Range of that the bones they called parts of the premaxillae, studied length of relative and that others called nasals, are really pre­ Species (N) denticulated area length nasals. This matter needs to be resolved. Makaira nigricans 8 .02 .00-.03 In contrast, the istiophorid bill has paired pre­ Makaira indica 4 .05 .04-.07 nasal bones (Fig. I), is rounded in cross-section, Tetrapturus audax 6 .12 .03-.19 lacks any central chambers, and denticles adorn Istiophorus platypterus 4 .34 .08-.63 its ventral and generally its dorsal surfaces. The TetrapturuJalbiduJ 9 .75 .57·.78 BILLFISH PALEONTOLOGY 13 PM M A Figure I. Skull and lower jaw of a blue marlin (Makaira nigricans Lacepede, 1802). left lateral view. Composite illustration by Charles Bloomer primarily from a 43.3 kg (95.5 lb) '( caught off Kailua-Kona. HI. Bones labeled as follows: Articular (A). Dentary (D). Frontal (F), Lateral ethmoid (LE), Maxillary (M), Nasal (N), Predentary (PD). Premaxillary (PM), Prenasal (PN). 13 6 ...._-.1__......__...1-__""-__...._....1 4 5 6 7 8 9 10 DEPTH X 10-1 .5l Figure 2. Simple regression of depth (D) and width (W) of 43 rostra measured at mid-rostrum length (.5L) for six species of billfishes. Rostrum length (L) was determined by measuring the straight-line distance from the distal tip to the anterior orbital margin of the lateral ethmoid. Istiophorus platypterus ('*'), n =4; Makaira indica ( X), n = 5; M. nigricans (e), n = 15; M. panamensis (0), n = I; Tetrapturus albidus (*), n = 9; T. audax (+), n =9. 14 PLANNING THE FUTURE OF BILLFISHES normal specimen. Additional specimens have a (Nakamura 1983). The surface of the scapula small, well-developed predentary bone and a that articulates with the large first pectoral ray lower jaw with an intermandibular joint. is flat in the black marlin, whereas the same Other skull bones. Billfishes differ in the surface in other istiophorids is round (Wapenaar proportions of their skulls. For example, the and Talbot 1964). Fierstine and Welton (1983) Xiphiidae have a short post-orbital region and noted that the articular surface