Copeia, 2005(3), pp. 665±672 Grouped Tooth Replacement in the Oral Jaws of the Tripletail, Lobotes surinamensis (Perciformes: Lobotidae), with a Discussion of Its Proposed Relationship to Datnioides ERIC J. HILTON AND WILLIAM E. BEMIS Lobotes surinamensis is a widely distributed marine perciform and is the sole mem- ber of the family Lobotidae, which has unclear phylogenetic af®nities. In this paper we describe and illustrate a mode of tooth replacement in Lobotes that we name ``grouped'' tooth replacement. Lateral oral teeth are replaced intraosseously, i.e., developing replacement teeth can clearly be seen beneath them within both the dentary and premaxillary bones. In contrast to the more typically seen pattern of alternate replacement, the replacement teeth of Lobotes develop as a group within the bone, lying directly beneath the group of teeth that they will replace. Within each tooth replacement group, the teeth show an anteroposterior gradient in age. Within the category of fully functional teeth there is a clear anterior to posterior gradient of eruption within a tooth group. Grouped tooth replacement may be a synapomorphy of Lobotes and Datnioides.AsinLobotes, the lateral oral teeth of Dat- nioides also are replaced intraosseously and in groups, although they are smaller and the groups are neither as distinct nor as regular. The signi®cance and polarity of this character, as well as other osteological similarities of Lobotes and Datnioides,are dif®cult to evaluate given the lack of understanding of higher level relationships among perciforms and the paucity of information about modes of their tooth re- placement. OBOTES surinamensis, commonly known as morphology of larvae and small juveniles (#23 L the tripletail or black®sh, is a widely dis- mm SL) in their study of development in this tributed marine perciform found in the Atlan- species. tic, eastern Paci®c, and Indo-West Paci®c. It oc- In this paper we describe an unusual mode curs primarily in tropical and sub-tropical waters of tooth replacement in the oral jaws of Lobotes. but at least occasionally enters temperate wa- Tooth replacement of ®shes has received inter- ters, and has been described as a ``slothful, slug- mittent but focused study, both as a general gish animal, much preferring to drift with the phenomenon (e.g., Tomes, 1876; Edmund, currents to take it where they will than to set a 1960; Osborn, 1977) and in speci®c groups of course and go to it'' (Shipp, 1994:147). Lobotes ®shes (e.g., Moy-Thomas, 1934; Miller and Rad- surinamensis is the sole valid species of the nine nor, 1973; Johnson, 1986). Fink (1981) de®ned nominal species in the genus (Eschmeyer, 1998: tooth attachment types in actinopterygians, and 2356). As have many authors (e.g., Weber and most recently, Trapani (2001) detailed various de Beaufort, 1936; Springer, 1982; Carpenter, patterns of tooth replacement in teleostean ®sh- 2001), Nelson (1994:359) included the genera es. He recognized two distinct patterns: extraos- Lobotes and Datnioides (5 Coius of some authors; seus replacement, in which the replacement see Roberts and Kottelat, 1994; Kottelat, 2000) tooth develops outside of the bone and solely in the family Lobotidae, although he acknowl- within soft tissue before attaching to a tooth- edged that there is ``no ®rm evidence that Lo- bearing bone; and intraosseus replacement, in botes and Datnioides form a monophyletic which the replacement tooth develops within group.'' In contrast, Eschmeyer (1998) placed the bone to which it will eventually attach. With- them in different families (i.e., Lobotidae and in each of these broad categories of tooth re- Datnioididae, as Coiidae; see Kottelat [2000] for placement, there are variations on a theme, discussion of the family name of Datnioididae). both within a taxon (i.e., tooth replacement on The phylogenetic af®nities of these genera, different dentigerous bones) and between taxa. both to each other and to other members of Here, we ®rst describe the structure of the oral Perciformes, remain unclear. Also the anatomy jaws of L. surinamensis. We then describe and of Lobotes is poorly known. Johnson (1984) de- illustrate the mode of tooth replacement in Lo- scribed aspects of cranial ornamentation in the botes that we name ``grouped'' tooth replace- larvae and Ditty and Shaw (1994) described the ment. We conclude by reviewing some patterns q 2005 by the American Society of Ichthyologists and Herpetologists 666 COPEIA, 2005, NO. 3 Fig. 1. Left oral jaws of Lobotes surinamensis (UMA F10891; 459 mm SL). (A) Lateral view. (B) Medial view. Anterior facing left (images in B reversed). Abbreviations: ang-ar 5 anguloarticular, a.pr 5 ascending process, cm 5 coronomeckelian, cpr.ang-ar 5 coronoid process of the anguloarticular, cpr.d 5 coronoid process of the dentary, d 5 dentary, m.pr 5 maxillary process of the premaxilla, mx 5 maxilla, pmx 5 premaxilla, pmx.pr 5 premaxillary process of the maxilla, rar 5 retroarticular. of tooth replacement in perciforms and noting F10927 (508 mm SL); UMA F11141 (398 mm the similarity in the pattern of tooth replace- SL). Skeletons of several additional perco- ment in Lobotes and Datnioides, which may rep- morph taxa were also studied and include: Can- resent a putative synapomorphy for these gen- thidermis sp. (UMA F10413, 275 mm SL); Caranx era. hippos (UMA F10954, 233 mm SL); Cynoscion sp. (UMA F10555, 276 mm SL); Datnioides quadri- MATERIALS AND METHODS fasciatus (AMNH 94466SD, est. 250 mm SL; AMNH 37993SD, SL unknown but .300 mm); All but one specimen of L. surinamensis used Lutjanus campechanus (UMA F10962, 665 mm in this study were prepared as dry skeletons SL); Morone saxatils (UMA F10192, SL un- (FMNH 20643 is a cleared-and-stained speci- known); Mycteroperca bonaci (UMA F10944, est. men prepared following a protocol modi®ed 460 mm SL); Orthopristis chrysoptera (UMA from Dingerkus and Uhler, 1977). All newly col- F10216, est. 165 mm SL); Paralichthys lethostig- lected specimens (i.e., the UMA specimens) mata (UMA F11065, 410 mm SL); Pomatomus sal- were prepared following the method outlined tatrix (UMA uncat., SL unknown); Scomberomorus by Bemis et al. (2004). The oral jaws of some maculatus (UMA F10228, est. 600 mm SL); Sphy- specimens were removed from the rest of the raena barracuda (UMA F11026, 1050 mm SL); skeleton and soaked in a weak solution of Stizostedion vitreum (UMA F10204, est. 470 mm household ammonia and any remaining tissue SL). was removed by hand. Institutional abbreviations follow Leviton et RESULTS al. (1985) with the addition of UMA for the Uni- versity of Massachusetts Amherst Zoological Col- Description of the oral jaws.ÐThe oral jaws of Lo- lections. The following specimens of Lobotes botes are illustrated in Figure 1. The upper jaws were examined: ANSP 77947 (est. 200 mm SL); consist of the premaxillae and maxillae and, as FMNH 20643 (est. 50 mm SL); UMA F10698 usual for acanthomorph ®shes, only the pre- (450 mm SL); UMA F10704 (440 mm SL); UMA maxillae bear teeth. The relatively slender max- F10891 (459 mm SL); UMA F10892 (425 mm illa terminates posteroventrally in a laterally ¯at- SL); UMA F10924 (566 mm SL); UMA F10925 tened hook. The maxilla is tightly associated (505 mm SL); UMA F10926 (425mm SL); UMA with the dorsolateral surface of the premaxilla, HILTON AND BEMISÐTOOTH REPLACEMENT OF LOBOTES 667 and the premaxillary process of the maxilla par- tially wraps around the maxillary process of the premaxilla. The lateral surface of the maxilla bears a distinct triangular process for the inser- tion of the maxillo-mandibular ligament or the ligamentum primordium. The well-developed ascending process of the premaxilla is continu- ous with the maxillary process. The lower jaw of Lobotes consists of the den- tary, anguloarticular, retroarticular, and coron- omeckelian. The dentary and the anguloarti- cular are the largest elements of the lower jaw, forming much of the anterior and posterior halves, respectively. Both the dentary and an- guloarticular bear well-developed coronoid pro- cesses that are offset from their dorsal margins. The relatively small retroarticular forms the pos- teroventral corner of the lower jaw, and is com- pletely removed from the quadrate articulatory Fig. 2. Left oral jaws of Lobotes surinamensis in lat- surface. The small coronomeckelian sits imme- eral view to show general arrangement of groups of diately anterior to the junction between Meck- replacement teeth (UMA F10698; 450 mm SL); an- el's cartilage and the anterior portion of the an- terior facing left. The premaxilla has ten replacement gular. groups, denoted by rg1 to rg10. The dentary has nine replacement groups. Each replacement group con- sists of between one and ®ve teeth associated with a Tooth replacement.ÐBoth the dentary and pre- replacement pore (for a single incoming tooth) or slit maxilla of Lobotes bear medial and lateral series (for multiple incoming teeth). Within each replace- of teeth. The medial series consist of small con- ment slit, there is a maximum of four teeth. Anterior ical teeth that form a shagreen on the bone of to left; scale bar equals 10 mm. attachment (Fig. 1B). Nothing is noteworthy about tooth replacement patterns for the me- dial series, for the teeth are replaced individu- through either a pore (for a replacement group ally as is typical for other teleosts. The lateral that consists of only one tooth) or a slit (for a series consist of large, antero-posteriorly ¯at- replacement group that consists of more than tened teeth that, when fully functional, are ®rm- one tooth). The pores and slits represent the ly ankylosed to their bone of attachment (al- physical space through which the dental lamina though no determination of the degree of min- passed from the jaw epithelium to the enamel eralization of the ankylosis was made; e.g., Fink, organ that is needed for cap development in 1981).