Figure 7. Occlusal features from casts of lower second molars of (A) Eulemur rubriven-ter (RMNH m) and (B) Propithecus diadema edwardsi (RMNH b). Not to scale. Note: no distinct entoconid on E. rubriventer specimen (photos by Ny Yamashita).
Phaner possessing a hypoconulid on M3 and exceptionally low, rounded cusps in Cheirogaleus (Tattersall, 1982). Cuozzo (2000) has reported a great deal of morphological variation in the dentition of a large sample (n=126) of mouse lemurs (Microcebus c.f. murinus) housed at the American Museum of Natural History (Buettner-Janusch and Tattersall, 1985). For example, approximately 7% of the individuals in this sample exhibit a distinct, variably developed lingual cusp, originating from the cingulum disto-lingual to the hypocone on the first maxillary molar (Cuozzo, 2000). In addition, at least one individual in the sample displays this trait on M2 (Cuozzo, 2000). Even the presence of an M3 hypoconulid, a trait viewed as diagnostic of the cheirogaleids (e.g., Tattersall, 1982), varies in this sample (Cuozzo, 2000). Indriids have retained the paraconid and have a hypoconulid on the third molar only. The indriid trigonid is on the same occlusal plane as the talonid (Schwartz and Tattersall, 1985). Strong transverse crests connect the anterior and posterior cusps to approach a bilophodont condition that is fully realized in Indri.
For many years the focus of morphological study of lemur teeth has emphasized interspecific differences and lemur taxonomy (e.g., Schwartz and Tattersall, 1985; Swindler, 2002; Tattersall, 1982). More recently, work on a limited number of large samples of extant lemurs has allowed for a better understanding of dental variation, which has implications for addressing a variety of questions in primate paleontology and lemur taxonomy (e.g., Cuozzo, 2000; Cuozzo et al., 2004; Sauther et al., 2001). In the set of 23 dental traits used by Tattersall and Schwartz (1991) and Tattersall (1993) in their analyses of extant lemur taxonomy (critiqued by Groves and Trueman, 1995), 9 show a distinction between L. catta and the other lemurids (e.g., Eulemur, Varecia). In a pair of studies examining dental variation in the ring-tailed lemurs at Beza Mahafaly (Cuozzo et al., 2004; Sauther et al., 2001), two of these traits do not show a distinction. This includes the presence of several individuals that display distinct protostyles on the lingual cingula of the maxillary molars (Cuozzo et al., 2004), and roughly half of the population exhibiting distinct metaconids on P4 (Cuozzo et al., 2004; Sauther et al., 2001). The maxillary molar protostyles seen in some individuals at Beza Mahafaly (compare Figures 8 and 9) are exactly what one would expect in other lemurids, such as Eulemur fulvus (e.g., Swindler, 2002; Tattersall, 1982, 1993).
In contrast to molecular data, in which L. catta is most closely allied with Hapalemur (e.g., Karanth et al., 2005; Poux et al., 2005), these dental data suggest that L. catta and the other lemurids are more similar dentally than has generally been recognized (Cuozzo et al., 2004). This example, along with our discussion of dental variation in mouse lemurs, emphasizes the need for large samples when considering traits used in systematic and phylogenetic analyses, and indicates that morphological variation, even within single populations, is pronounced in extant lemurs. Understanding the degree of dental variation in extant lemur species therefore has a number of implications for interpreting variation in fossil assemblages and identifying species in the primate fossil record (Cuozzo, 2000, 2002; Cuozzo et al., 2004; Sauther et al., 2001).
Figure 8. Lingual molar morphology as shown in a cast of an adult ring-tailed lemur from Beza Mahafaly (Hot Pink II 199) with distinct protostyles (black arrows) common to species of Eulemur (photo by Frank Cuozzo).
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