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.