Basic Morphology

Maxillary incisors range within and among Malagasy lemurs from entirely absent (Lepilemur) or reduced (lemurids, Avahi) to relatively prominent (cheirogaleids, indriids) (see Table 1) (Martin, 1972; Tattersall, 1982). Maxillary canine size varies considerably among lemurs, with some taxa exhibiting very large (i.e., high) canines, relative to first molar size (see Table 3 in Godfrey et al., this volume). Daubentonia has no permanent canines (Swindler, 2002; Tattersall, 1982). In Hapalemur, the maxillary canine is comparatively short and robust, especially so in H. simus (Milton, 1978). In contrast, Lemur catta displays large, prominent maxillary canines (Figure 1). Although Malagasy strepsirhines are generally viewed as dentally monomorphic (e.g., Kappeler, 1996), a view supported in numerous studies (e.g., Lawler et al., 2005), some taxa do exhibit significant sexual dimorphism in favor of either males or females (e.g., Kappeler, 1996). For example, a recent study of brown lemurs (Eulemur) (Johnson et al., 2005) indicates a contrast in maxillary canine height between E. albocollaris and E. fulvus rufus, with E. albocollaris displaying significant male-biased canine height dimorphism. However, the patterns of sexual dimorphism seen among lemurs are not consistent with those in anthropoid primates, as to date, hypotheses concerning intermale competition, female dominance, and mating system do not display a clear correspondence among lemurs (Kappeler, 1996). In addition to their large, projecting canines, ring-tailed lemurs exhibit a high degree of metric variability in both canine length (e.g., Cuozzo and Sauther, 2004a; Sauther et al., 2001) and height (e.g., Kappeler, 1996). Metric variability in anterior teeth (when compared to the postcanine dentition) can indicate sexual dimorphism in primates, including fossil forms (e.g., Gingerich, 1995). Given the large canines and intense intermale aggression seen in ring-tailed lemurs, significant (anthropoid-like) canine dimorphism would not be unexpected, as suggested by Kappeler's (1996) work. Preliminary data from the ring-tailed lemurs at Beza Mahafaly indicate

Figure 1. Projecting maxillary canine (white arrow) in a male Lemur catta (Black 240) from Beza Mahafaly (photo courtesy of Michelle Sauther).

significant male-biased canine height dimorphism (Sauther and Cuozzo, unpublished data).

The mandibular anterior teeth of lemurs are elaborated into a toothcomb, which represents a diagnostic character for all strepsirrhines. As such, there are few departures from the basic structure across Malagasy lemur families. The basic morphology involves integration of the two incisors plus the canine from each side to form a procumbent six-tooth comb (Figure 2). There is a loss of one tooth per side in the indriids, which leaves a comb comprised of an incisor and a canine (Schwartz, 1974, 1978) or two incisors (Gingerich, 1977) (Figure 3). In Daubentonia, the toothcomb, as well as the maxillary anterior tooth, has been further reduced to a single, continuously growing (hypselodont) tooth that has been identified as an incisor (Swindler, 2002) or a canine (Tattersall, 1982) (Figure 4). The anterior premolar among lemurs is often caniniform (Figure 2) (Swindler, 2002; Tattersall, 1982).

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