Grouped Tooth Replacement in the Oral Jaws of the Tripletail, Lobotes surinamensis (Perciformes: Lobotidae), with a Discussion of Its Proposed Relationship to Datnioides
Lobotes surinamensis is a widely distributed marine perciform and is the sole member of the family Lobotidae, which has unclear phylogenetic affinities. 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. As in Lobotes, the lateral oral teeth of Datnioides also are replaced intraosseously and in groups, although they are smaller and the groups are neither as distinct nor as regular. The significance and polarity of this character, as well as other osteological similarities of Lobotes and Datnioides, are difficult to evaluate given the lack of understanding of higher level relationships among perciforms and the paucity of information about modes of their tooth replacement.Abstract
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 = anguloarticular, a.pr = ascending process, cm = coronomeckelian, cpr.ang-ar = coronoid process of the anguloarticular, cpr.d = coronoid process of the dentary, d = dentary, m.pr = maxillary process of the premaxilla, mx = maxilla, pmx = premaxilla, pmx.pr = premaxillary process of the maxilla, rar = retroarticular
Left oral jaws of Lobotes surinamensis in lateral view to show general arrangement of groups of replacement teeth (UMA F10698; 450 mm SL); anterior facing left. The premaxilla has ten replacement groups, denoted by rg1 to rg10. The dentary has nine replacement groups. Each replacement group consists of between one and five teeth associated with a replacement pore (for a single incoming tooth) or slit (for multiple incoming teeth). Within each replacement slit, there is a maximum of four teeth. Anterior to left; scale bar equals 10 mm
Details of oral tooth attachment and replacement in Lobotes surinamensis (UMA F10698; 450 mm SL). All images are of the right premaxillae, reversed so that anterior faces left. (A) Occlusal view showing four tooth-replacement groups (rg3 to rg6) and the medial shagreen series of teeth (mst). (B) Photograph in lateral view. Replacement groups rg3 to rg6 are indicated and tooth loci are numbered 5 to 23. (C) X-ray in lateral view. Teeth at loci 11, 15, and 20 represent incoming teeth in which collar mineralization has not yet developed; such teeth are described as “incoming 2” (see text for explanation). Functional teeth in replacement group 4 are marked to show their relative ages. The oldest attached tooth in replacement group 4 is indicated by m1; note that its pulp cavity has largely been filled with mineralized dentine. The youngest extant tooth in replacement group 4 is indicated by m3; note that its pulp cavity is more open than is the pulp cavity of m1. (D) Line drawing matching images in B and C. Fully functional (i.e., firmly ankylosed) teeth are shaded black. Incoming 1 teeth, which are deeply set within replacement slits, lack any connection to the bone and are left white. Incoming 2 teeth are shaded gray
Left oral jaws of Datnioides quadrifasciatus (AMNH 94466SD; est. 300 mm TL). (A) Jaws in lateral view. (B) Anterior portion of the dentary. (C) Close-up of some teeth also presented in B showing detail of a similar mode of tooth replacement as described for Lobotes. Scale in B and C in millimeters; anterior facing left in all. Abbreviations: ang-ar = anguloarticular, a.pr = ascending process, cm = coronomeckelian, cpr.ang-ar = coronoid process of the anguloarticular, cpr.d = coronoid process of the dentary, d = dentary, mx = maxilla, pmx = premaxilla, pmx.pr = premaxillary process of the maxilla, rar = retroarticular
Contributor Notes
(EJH) Division of Fishes, Smithsonian Institution, P.O. Box 37012, NMNH Rm. WG-12, MRC 0159, Washington, D.C. 20013–7012; and (WEB) Department of Ecology and Evolutionary Biology, Corson Hall, Cornell University, Ithaca, New York 14853. (EJH) Hilton.Eric@nmnh.si.edu; (WEB) web24@cornell.edu Send reprint requests to EJH.